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Medication-induced prolongation of the QT-interval (miQTP) can lead to cardiac arrhythmia. Our aim was to investigate the prevalence of forensic autopsy cases where fatal cardiac arrhythmia related to treatment with QT-prolonging medications (QT-PMs) could be suspected. We performed a cross-sectional study of 741 forensic autopsies undertaken at our institution in non-drug addicts aged 15 years or above from 2017 to 2019. We defined a high risk of miQTP by one detected QT-PM in a concentration above therapeutic level, or two or more detected QT-PMs in post mortem blood. We reviewed the autopsy reports from cases with a high miQTP-risk to identify cases with no other apparent cause of death. We discarded suicides and cases with lethal levels of QT-PMs. We identified 167 cases (22.5%) with high risk of miQTP, and discarded 36 suicides (4.9%) and 7 (0.9%) with lethal levels of QT-PMs. Apart from a high risk of miQTP, no other apparent explanation of the cause of death was present in seven (0.9%). In 18 cases (2.4%) with high miQTP-risk, the cause of death was primarily attributed to cardiac changes other than acute cardiovascular events. In conclusion, 22.5% had a high risk of miQTP, and fatal cardiac arrhythmia related to treatment with QT-PMs could be suspected in 0.9%. However, a genetic pro-arrhythmic background could not be excluded in our study. Furthermore, it is possible that QT-PMs could have played a role in some of the 2.4% of cases where the cause of death was mainly attributed to cardiac changes and the risk of miQTP was high., Competing Interests: Declarations of interest The authors have no conflicts of interest to declare., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

Ethnopharmacological Relevance: Lagopsis supina (Steph.) Ik. -Gal. ex Knorr. has been widely used as a remedy treatment for diuresis and edema in China over 2500 years. Our previous results showed that the aqueous soluble fraction from L. supina (LSB) possessed acute diuretic effect., Aim of the Study: The aim of this study was to appraise the acute (6 h) and prolonged (7 d) diuretic effects, underlying mechanisms, and chemical profiling of LSB., Materials and Methods: The chemical profiling of LSB was performed by ultra-high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UHPLC-qTOF-MS/MS). Then, oral administration of LSB (40, 80, 160 and 320 mg/kg) and furosemide (10 mg/kg) once daily for 7 consecutive days to evaluate the diuretic effects in saline-loaded rats. The body weight, food consumption, and water intake were recorded once daily. The urinary volume, pH and electrolyte concentrations (Na + , K + , Cl - , and Ca 2+ ) were measured after administration drugs for acute and prolonged diuretic effects. In addition, the serum levels of Na + -K + -ATPase, angiotensin II (Ang II), anti-diuretic hormone (ADH), aldosterone (ALD), atriopeptin (ANP), aquaporins (AQPs)-1, 2 and 3 were determined by ELISA kits. The mRNA expressions and protein levels of AQPs-1, 2 and 3 were analyzed by real-time quantitative PCR and Western blot assays, respectively., Results: 30 compounds were identified in LSB based on accurate mass and MS/MS fragmentation compared to literature, among which phenylpropanoids and flavonoids could be partly responsible for the major diuretic effect. Daily administration of LSB (160 or 320 mg/kg) prominently increased urinary excretion volume after the 2 h at the first day of treatment, remaining until the 7th day. LSB did not cause Na + and K + electrolyte abnormalities, and has minor effect on Cl - and Ca 2+ concentrations at 320 mg/kg. Furthermore, LSB observably suppressed renin-angiotensin-aldosterone system (RAAS) activation, including decreased serum levels of Ang II, ADH, and ALD, and prominently increased serum level of ANP in rats. LSB treatment significantly down-regulated the serum levels, mRNA expressions and protein levels of AQP1, AQP2, and AQP3., Conclusion: LSB has a prominent acute and prolonged diuretic effects via suppression of AQP and RAAS pathways in saline-loaded rats, and support the traditional folk use of this plant. Taken together, LSB might be a potential diuretic agent., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The third trimester of pregnancy is related to physiological changes that can modify the process of absorption, distribution, metabolism, and excretion and, consequently, the efficacy and toxicity of drugs. However, little is known about furosemide pharmacokinetics and placental transfer in pregnancy. This study evaluated the maternal-fetal pharmacokinetics and distribution to amniotic fluid of furosemide in hypertensive parturient women under cesarean section. Twelve hypertensive parturient women under methyldopa (250 mg/8 h) and/or pindolol (10 mg/12 h) treatment received a 40-mg single oral dose of furosemide 1 to 10 hours before delivery by cesarean section. Blood and urine samples were collected for 12 hours after furosemide administration. At delivery, samples were obtained from maternal and umbilical cord blood (n = 8) to assess the transplacental transfer. Amniotic fluid (n = 4) was collected at the time of delivery. The following furosemide pharmacokinetic parameters were obtained as median (interquartile range): C max , 403 ng/mL (229 to 715 ng/mL); T max , 2.00 hours (1.50 to 4.83 hours); elimination half-life (t 1/2 ), 2.50 hours (1.77 to 2.97 hours); AUC 0-12 h , 1366 ng⋅h/mL (927 to 2531 ng⋅h/mL); AUC 0-∞ , 1580 ng⋅h/mL (1270 to 2881 ng⋅h/mL); CL/F 25.3 L/h (13.8 to 31.4 L/h); CLR, 2.50 L/h (1.77 to 2.97 L/h); CLNR, 22.7 L/h (12.1 to 25.6 L/h); and V d /F 82.8 L (34.4 to 173 L). The transplacental transfer of furosemide was 0.43 (0.10 to 0.73), and the amniotic fluid concentration was 11.0 ng/mL (5.51 to 14.6 ng/mL). From a clinical point of view, these results suggest that substrates of uridine diphosphate-glucuronosyltransferase isoenzymes such as furosemide may have increased clearance during pregnancy and could require dose adjustment in this population., (© 2020, The American College of Clinical Pharmacology.)

Many drug candidates have shown significant renoprotective effects in preclinical models; however, there is no clinically used effective pharmacotherapy for acute kidney injury. The failure to translate from bench to bedside could be due to misleading results from experimental animals with undetected congenital kidney defects. This study was performed to assess the effects of congenital hydronephrosis on the functional capacity of tubular renal transporters as well as kidney sensitivity to ischemia-reperfusion (I-R)-induced injury in male Wistar rats. Ultrasonography was used to distinguish healthy control rats from rats with hydronephrosis. L-carnitine or furosemide was administered, and serial blood samples were collected and analyzed to assess the effects of hydronephrosis on the pharmacokinetic parameters. Renal injury was induced by clamping the renal pedicles of both kidneys for 30 min with subsequent 24 hr reperfusion. The prevalence of hydronephrosis reached ~30%. The plasma concentrations after administration of L-carnitine or furosemide were similar in both groups. I-R induced more pronounced renal injury in the hydronephrotic rats than the control rats, which was evident by a significantly higher kidney injury molecule-1 concentration and lower creatinine concentration in the urine of the hydronephrotic rats than the control rats. After I-R, the gene expression levels of renal injury markers were significantly higher in the hydronephrotic kidneys than in the kidneys of control group animals. In conclusion, our results demonstrate that hydronephrotic kidneys are more susceptible to I-R-induced damage than healthy kidneys. Unilateral hydronephrosis does not affect the pharmacokinetics of substances secreted or absorbed in the renal tubules., (© 2020 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.)

Purpose: Toxicological screenings for identifying antihypertensive drugs proved to be a useful tool for assessing adherence. However, misinterpretation may occur in case of highly metabolised drugs with low renal excretion, as well as for drugs with a prolonged detectability. The aim of the present study was to compare a recently developed therapeutic drug monitoring (TDM) method based on serum concentrations to an urine drug detection method for assessing adherence in outpatients. Materials and methods: Corresponding urine and blood samples were obtained at the same time from 26 outpatients without supervised medication. Urine and serum analyses were performed using established high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) methodologies. Adherence was assumed if drugs were detectable in urine or if serum concentrations were above individually calculated lower dose-related concentrations (DRC) or literature-based therapeutic reference ranges (TRR) used as cut-off, respectively. Results: The identification of analytes in urine as well as the quantitative serum assay were performed for atenolol ( n  = 6 patients), bisoprolol ( n  = 8), nebivolol ( n  = 6), canrenone ( n  = 6, metabolite of spironolactone), hydrochlorothiazide ( n  = 12) and furosemide ( n  = 2). On the basis of drug detectability in urine, adherence was assumed in 88% of prescriptions. In 81% (DRC) and 50% (TRR) of the serum analyses the cut-off value was exceeded, which confirms patients' adherence in a lower number. Differences in adherence rates were found in five patients, mainly for β-blockers. Conclusion: This study suggests that assessment of adherence can be performed more precisely on the basis of serum drug concentrations with individually calculated lower DRC than by using the TRR or qualitative urinalysis.

Hypertension (HTN) is a significant risk factor for cardiovascular morbidity and mortality. Metabolic abnormalities, including adverse cholesterol and triglycerides (TG) profiles, are frequent comorbid findings with HTN and contribute to cardiovascular disease. Diuretics, which are used to treat HTN and heart failure, have been associated with worsening of fasting lipid concentrations. Genome-wide meta-analyses with 39,710 European-ancestry (EA) individuals and 9925 African-ancestry (AA) individuals were performed to identify genetic variants that modify the effect of loop or thiazide diuretic use on blood lipid concentrations. Both longitudinal and cross sectional data were used to compute cohort-specific interaction results, which were then combined through meta-analysis in each ancestry. These ancestry-specific results were further combined through trans-ancestry meta-analysis. Analysis of EA data identified two genome-wide significant (p < 5 × 10 -8 ) loci with single nucleotide variant (SNV)-loop diuretic interaction on TG concentrations (including COL11A1). Analysis of AA data identified one genome-wide significant locus adjacent to BMP2 with SNV-loop diuretic interaction on TG concentrations. Trans-ancestry analysis strengthened evidence of association for SNV-loop diuretic interaction at two loci (KIAA1217 and BAALC). There were few significant SNV-thiazide diuretic interaction associations on TG concentrations and for either diuretic on cholesterol concentrations. Several promising loci were identified that may implicate biologic pathways that contribute to adverse metabolic side effects from diuretic therapy.

Background: The primary objective of this study was to assess the disposition of furosemide in Thoroughbred horses treated intravenously with 1 mg/kg of furosemide 4 and 24 h before supramaximal treadmill exercise without and with controlled access to water, respectively. Another objective was to determine whether furosemide was detectable in the plasma of horses after exposure to supramaximal treadmill exercise. Thoroughbred horses (n = 4-6) were administered single intravenous doses of 1 mg/kg of furosemide at 4 and 24 h before supramaximal exercise on a high-speed treadmill, with controlled and free access to water, respectively. Plasma furosemide concentrations were determined using liquid chromatography., Results: Furosemide was detected in all the horses, regardless of whether they were treated 24 h or 4 h before excersice. In both treatment sequence groups of 2 horses, the concentration time profiles of furosemide during the first 4 h after its administration were relatively similar. The average maximum observed concentrations, AUC 0-1.5h, and AUC 0-3h , of both groups of horses were not different (p > 0.05). There were no significant differences in systemic clearance based on the geometric mean (95% confidence interval) (409 (347-482) mL/h/kg) for 4 h and 320 (177-580) mL/h/kg) for 24 h) between horses that were exercised 4- and 24-h post-furosemide administration. The plasma concentration of furosemide in all the horses fell below the limit of quantification (25 ng/mL) within 12 h after drug administration. In the group treated 24 h before exercise, none of the horses had detectable furosemide at the time of supramaximal treadmill exercise. In the group treated 4 h before exercise, furosemide was detected 1 h before and 2 h after supramaximal treadmill exercise in 4/4 and 3/4 horses, respectively. The mean AUC 3-last h of both groups of horses were not different (p > 0.05)., Conclusions: Water restriction did not exert any apparent effect on the disposition of furosemide. It remains to be determined, however, whether the attained plasma concentration of furosemide in combination with other controlled water access protocols have any direct or indirect pharmacological effect that may affect the athletic performance of the horse.

Background: This study assessed the contribution of intracorporeal (IC) and extracorporeal clearance (EC) of furosemide in patients with septic acute kidney injury (AKI), and the relationship between plasma concentrations and urine volume., Methods: Prospective cohort observational study of 15 patients with septic AKI undergoing continuous veno-venous hemodiafiltration (CVVHDF) divided according to urine volume (< 500 ml/12 h, Oliguria group, n = 5; > 500 ml/12 h, Diuresis group, n = 10) during continuous infusion of furosemide (120 mg/12 h) at steady-state condition. Plasma and effluent furosemide concentrations were determined by high-performance liquid chromatography (HPLC)-mass spectrometry every 12 h for 48 h., Results: Furosemide plasma concentrations and total body clearance (TBC) were 6.14 mg/l and 22.1 ml/min for the Oliguria group, and 2.63 mg/l and 54.4 ml/min for the Diuresis group, respectively (p < 0.05). When urine volume was < 500 ml/24 h, the furosemide plasma concentrations peaked at the potentially toxic value of 13.0 mg/l. Furosemide EC was not relevant for the Diuresis group, but it represented 18% of TBC for the Oliguria group. Furosemide plasma concentrations correlated positively with dose infusion for both groups (r = 0.728 and 0.685, p < 0.05), and negatively with urine volume only for the Diuresis (r = - 0.578, p < 0.01) but not for the Oliguria group (r = - 0.089, p = 0.715)., Conclusions: For patients with urine volume > 500 ml/12 h continuous infusion of furosemide up to 480 mg/24 h leads to increasing urine volume, which can predict furosemide plasma levels within its safety range. When the urine volume is lower, the furosemide plasma levels are increased beyond any further diuretic efficacy.

Objectives: To determine the relationship between theophylline trough levels and urine output in critically ill children administered aminophylline as adjunctive diuretic therapy., Design: Retrospective cohort study., Setting: The PICU of a tertiary care children's hospital., Patients: A mixed population of medical/surgical including postoperative cardiothoracic surgery patients less than 18 years old., Interventions: Electronic medical records of all PICU patients admitted from July 2010 to June 2015 were reviewed, and patients who received aminophylline as diuretic therapy were identified., Measurements and Main Results: Patient cohort data including demographics, daily aminophylline, furosemide and chlorothiazide dosing, theophylline trough levels, fluid intake, urine output and total fluid balance, blood urea nitrogen, and creatinine levels were abstracted. Multivariate analysis based on a generalized estimating equations approach demonstrated that aminophylline administration, when analyzed as a categorical variable, was associated with an increase in urine output and decreased fluid balance. However, aminophylline dosing, when analyzed as a continuous variable, was associated with neither an increase in urine output nor decreased fluid balance. Theophylline trough levels were not correlated with urine output at 24 hours (p = 0.78) and were negatively correlated with urine output at 48 hours (r = 0.078; p < 0.005)., Conclusions: Aminophylline administration provided a measure of increased diuresis, regardless of dosage, and theophylline trough levels. Therefore, achieving a prescribed therapeutic trough level may not be necessary for full diuretic effect. Because, as opposed to the diuretic effect, the side effect profile of aminophylline is dose-dependent, low maintenance dosing may optimize the balance between providing adjunctive diuretic effect while minimizing the risk of toxicity.

Background: Poor drug adherence in hypertensive patients can lead to treatment failure and increased cardiovascular morbidity, as well as increased costs to society. An analytical method based on ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MSMS) was developed and validated for use in routine therapeutic drug monitoring (TDM). The method includes 21 antihypertensive drugs or active metabolites from the groups beta blockers (n=5), calcium antagonists (n=5), angiotensin II receptor antagonists (n=4), angiotensin converting enzyme (ACE) inhibitors (n=3) and diuretics (n = 3), in addition to one α1-selective alpha blocker., Method: A 200 µL serum sample was handled automatically using a pipetting robot. Protein precipitation was performed with 600 µL of 1% formic acid in acetonitrile (v:v) and phospholipid removal was carried out using a Waters OSTRO™ 96-well plate. After evaporation and reconstitution the eluent was injected thrice with different inlet and mass spectrometric methods to cover the different physico-chemical properties of the drugs and the variations in therapeutic concentration ranges between drugs. Acquity UPLC BEH C18 (2.1x50mm, 1.7 µm) column equipped with a corresponding pre-column was used for chromatographic separation. For every analyte an isotopically labelled analogue served as internal standard, except for lisinopril where enalaprilat-d5 was used., Results: Accuracies were in the range of -13.7 to 13.2% and intra-day and inter-day precisions in the range of 1.1 to 10.5%. The linearity within the calibration ranges expressed as coefficient of determination was higher than 0.995 for all compounds. Matrix effects and recovery efficiencies were within acceptable limits. The limits of quantitation varied from 0.02 to 10.7 µg/L. The stability of the drugs in serum at different conditions was tested. Diltiazem was not stable at 4-8 °C with up to 23.5 % loss after six days. Degradation of atenolol, irbesartan, bendroflumethiazide, hydrochlorothiazide and diltiazem was observed when stored at 30 °C. The suitability of the method was demonstrated in a routine TDM setting, analysing samples from 127 patients undergoing antihypertensive drug treatment., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Diuretic treatment is the mainstay for management of congestive heart failure in horses, and its use has been restricted to injectable medications because no currently data supports the use of PO administered loop diuretics., Objectives: To determine the pharmacokinetic and pharmacodynamic properties of PO administered torsemide and, determine if PO administered torsemide, could be used as an alternative to injectable diuretics in the horse., Animals: Six healthy adult mares., Methods: A 2-phase, prospective study, that consisted of pharmacokinetic profiling of a single dose (6 mg/kg PO) and pharmacodynamic effects of long-term torsemide administration (2 mg/kg PO q12h) for 6 days in healthy horses., Results: Pharmacokinetic analysis identified a peak concentration (C max ) of 10.14 µg/mL (range, 6.79-14.69 µg/mL) and elimination half-life (T 1/2 ) 9.2 hours (range, 8.4-10.4 hours). The area under the plasma drug concentration over time curve (AUC) was 80.7 µg × h/mL (range, 56.5-117.2 µg × h/mL). A statistically significant increase in urine volume and decrease in urine specific gravity were found from day 0 (baseline) to day 6 (P < .0001). Significant alterations in biochemical variables included hyponatremia, hypokalemia, hypochloremia, and increased serum creatinine concentration. Mean arterial blood pressure significantly decreased on day 6 (57.7 ± 8.8 mm Hg, P = .001) as compared with baseline (78 ± 6.1 mm Hg). Serum aldosterone concentrations significantly increased after 6 days of torsemide administration (P = .0006)., Conclusions and Clinical Importance: PO administered torsemide (4 mg/kg/day) successfully reached therapeutic concentrations in blood, induced clinically relevant diuresis, and resulted in moderate pre-renal azotemia and electrolyte disturbances., (Copyright © 2018 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Aims: Sacubitril/valsartan is indicated for the treatment of heart failure and reduced ejection fraction (HFrEF). Furosemide, a loop diuretic commonly used for the treatment of HFrEF, may be coadministered with sacubitril/valsartan in clinical practice. The effect of sacubitril/valsartan on the pharmacokinetics and pharmacodynamics of furosemide was evaluated in this open label, two-period, single-sequence study in healthy subjects., Methods: All subjects (n = 28) received 40 mg oral single-dose furosemide during period 1, followed by a washout of 2 days. In period 2, sacubitril/valsartan 200 mg (97/103 mg) was administered twice daily for 5 days and a single dose of 40 mg furosemide was coadministered on day 6. Serial plasma and urine samples were collected to determine the pharmacokinetics of furosemide and sacubitril/valsartan and the pharmacodynamics of furosemide. The point estimates and the associated 90% confidence intervals for pharmacokinetic parameters were evaluated., Results: Coadministration of furosemide with sacubitril/valsartan decreased the maximum observed plasma concentration (C max ) [estimated geometric mean ratio (90% confidence interval): 0.50 (0.44, 0.56)], area under the plasma concentration-time curve (AUC) from time 0 to infinity [0.72 (0.67, 0.77)] and 24-h urinary excretion of furosemide [0.74 (0.69, 0.79)]. When coadministered with sacubitril/valsartan, 0-4-h, 4-8-h and 0-24-h diuresis in response to furosemide was reduced by ~7%, 21% and 0.2%, respectively, while natriuresis was reduced by ~ 28.5%, 7% and 15%, respectively. Post hoc analysis of the pivotal phase III Prospective comparison of ARNI with ACEI to Determine Impact on Global Mortality and morbidity in Heart Failure trial (PARADIGM-HF) indicated that the median furosemide dose was similar at baseline and at the end of the study in the sacubitril/valsartan group., Conclusions: Sacubitril/valsartan reduced plasma C max and AUC and 24-h urinary excretion of furosemide, while not significantly affecting its pharmacodynamic effects in healthy subjects., (© 2018 Crown copyright. British Journal of Clinical Pharmacology © 2018 British Pharmacological Society.)

Introduction: Diuretic failure is a potential life-ending event but is unpredictable and poorly understood. The objectives of this study were to evaluate pharmacodynamic markers of furosemide-induced diuresis and to investigate mechanisms of diuretic braking in dogs receiving constant rate infusion (CRI) of furosemide., Animals: Six healthy male dogs., Methods: Raw data and stored samples from one arm of a previously published study were further analyzed to mechanistically investigate causes of diuretic braking in these dogs. Urine volume was recorded hourly during a 5-h furosemide CRI. Urine and blood samples were collected hourly to measure serum and urine electrolytes, urine aldosterone, and plasma and urine furosemide. Serum electrolyte fractional excretion was calculated. Urine sodium concentration was indexed to urine potassium (uNa:uK) and urine furosemide (uNa:uFur) concentrations, plasma furosemide concentration was indexed to urine furosemide concentration (pFur:uFur), and urine aldosterone was indexed to urine creatinine (UAldo:C). Temporal change and the relationship to urine volume were evaluated for these measured and calculated variables., Results: Urine volume was significantly correlated with urine electrolyte amounts and with uNa:uK. The ratio of pFur:uFur decreased during the infusion, whereas furosemide excretion was unchanged., Conclusions: There was a strong relationship between urine volume and absolute urine electrolyte excretion. Urine volume was strongly correlated to uNa:uK, giving it potential as a spot indicator of urine production during diuresis. The decrease in uNa:uK over time during the infusion is consistent with mineralocorticoid modification of urinary electrolyte excretion, supporting renin-angiotensin-aldosterone activation as a cause of diuretic braking in this model., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Furosemide is a diuretic agent used commonly in racehorses to attenuate the bleeding associated with exercise-induced pulmonary hemorrhage (EIPH). The current study describes serum and urine concentrations and the pharmacokinetics of furosemide following administration at 4 and 24 hrs prior to maximal exercise. Eight exercised adult Thoroughbred horses received a single IV administration of 250 mg of furosemide at 4 and 24 hrs prior to maximal exercise on a high-speed treadmill. Blood and urine samples were collected at time 0 and at various times for up to 72 hrs and furosemide concentrations determined using liquid chromatography-tandem mass spectrometry. Serum furosemide concentrations remained above the LOQ (0.05 ng/ml) for 36 hrs in 3/8 and 1/8 horses in the 4- and 24-hrs groups, respectively. Serum concentration data were best fit by a two-compartment model. There was not a significant difference in the volume of distribution at steady-state (0.594 ± 0.178 [4 hrs] and 0.648 ± 0.147 [24 hrs] L/kg) or systemic clearance (0.541 ± 0.094 [4 hrs] and 0.617 ± 0.114 [24 hrs] L/hrs/kg) between horses that were exercised at 4- and 24 hrs postdrug administration. The mean ± SD elimination half-life was 3.12 ± 0.387 and 3.23 ± 0.407 hrs following administration at 4 and 24 hrs prior to exercise, respectively., (© 2017 John Wiley & Sons Ltd.)

Bumetanide is a loop diuretic that is proposed to possess a beneficial effect on disorders of the central nervous system, including neonatal seizures. Therefore, prediction of unbound bumetanide concentrations in the brain is relevant from a pharmacological prospective. A physiologically-based pharmacokinetic (PBPK) model was developed for the prediction of bumetanide disposition in plasma and brain in adult and paediatric populations. A compound file was built for bumetanide integrating physicochemical data and in vitro data. Bumetanide concentration profiles were simulated in both plasma and brain using the Simcyp PBPK model. Simulations of plasma bumetanide concentrations were compared against plasma levels published in the literature. The model performance was verified with data from adult studies before predictions in the paediatric population were undertaken. The adult and paediatric intravenous models predicted pharmacokinetic factors, namely area under the concentration-time curve, maximum concentration in plasma and time to maximum plasma concentration, within two-fold of observed values. However, predictions of plasma concentrations within the neonatal intravenous model did not produce a good fit with the observed values. The PBPK approach used in this study produced reasonable predictions of plasma concentrations of bumetanide, except in the critically ill neonatal population. This PBPK model requires more information regarding metabolic intrinsic clearance and transport parameters prior to further validation of drug disposition predictions in the neonatal population. Given the lack of information surrounding certain parameters in this special population, the model is not appropriately robust to support the recommendation of a suitable dose of bumetanide for use as an adjunct antiepileptic in neonates., (Copyright © 2018 John Wiley & Sons, Ltd.)

Background: Metolazone is a diuretic, saluretic and antihypertensive chemical compound from the quinazoline category that possesses medicinal features similar to those of other thiazide diuretic drugs. However, the pharmacokinetics of metolazone in the Chinese population has rarely been studied. This study aimed to examine the pharmacokinetic characteristics, safety characteristic, and tolerability of metolazone in healthy Chinese subjects after single and multiple doses taken orally as well as the effects that food and gender have on oral metolazone pharmacokinetic parameters., Methods: An open-label, randomized, and single- and multiple-dosing investigation was performed in healthy Chinese subjects. The investigation included 3 study groups: the 0.5 mg, 1 mg and 2 mg dose groups were the single-dose study groups in the first stage. Eligible volunteers were randomly and orally administered a single 0.5 mg, 1 mg, or 2 mg metolazone tablet. The 0.5 mg dose group was also part of the multiple-dose study group, and the 1 mg dose group was the food-effect study group in the second stage. Human plasma samples were gathered pre-dosing and up to 48 h after dosing. The human plasma sample concentration of metolazone was quantified using a validated liquid chromatography tandem mass spectrometry method. Pharmacokinetic data were calculated by a noncompartmental analysis method using WinNonlin version 6.4. Tolerability was evaluated based on adverse events, medical examination, 12-lead ECG, and other clinical laboratory exams., Results: Thirty eligible subjects (15 men and 15 women) were registered in our investigation and completed all of the study stages. The AUC and C max showed dose proportionality after a single dose based on the linear-regression analysis. A comparison of the pharmacokinetic data revealed that the differences between the male and female groups were not statistically significant. The t max of metolazone was increased by approximately 100% in the fed condition. Metolazone was well tolerated at the tested dose, and no adverse effects were observed., Conclusions: Single dosing with 0.5 mg, 1 mg, or 2 mg metolazone yielded linear plasma pharmacokinetic properties in healthy Chinese subjects. Multiple oral doses of metolazone did not display significantly different distributions or elimination characteristics from those observed for a single dose. Gender factors did not appear to influence the pharmacokinetic parameter variation of metolazone. The t max of metolazone increased in the fed condition. Metolazone was well tolerated at the tested dose in this study., Trial Registration: This investigation is retrospectively registered at chictr.org.cn (ChiCTR-IIR-17012929, October 09 2017).

Though numerous reports have demonstrated multiple mechanisms by which furosemide can exert its anti-hypertensive response. However, lack of studies describing PK-PD relationship for furosemide featuring its anti-hypertensive property has limited its usage as a blood pressure (BP) lowering agent. Serum concentrations and mean arterial BP were monitored following 40 and 80mgkg -1 multiple oral dose of furosemide in spontaneously hypertensive rats (SHR) and DOCA-salt induced hypertensive (DOCA-salt) rats. A simultaneous population PK-PD relationship using E max model with effect compartment was developed to compare the anti-hypertensive efficacy of furosemide in these rat models. A two-compartment PK model with Weibull-type absorption and first-order elimination best described the serum concentration-time profile of furosemide. In the present study, post dose serum concentrations of furosemide were found to be lower than the EC 50 . The EC 50 predicted in DOCA-salt rats was found to be lower (4.5-fold), whereas the tolerance development was higher than that in SHR model. The PK-PD parameter estimates, particularly lower values of EC 50 , K e and Q in DOCA-salt rats as compared to SHR, pinpointed the higher BP lowering efficacy of furosemide in volume overload induced hypertensive conditions. Insignificantly altered serum creatinine and electrolyte levels indicated a favorable side effect profile of furosemide. In conclusion, the final PK-PD model described the data well and provides detailed insights into the use of furosemide as an anti-hypertensive agent., (Copyright © 2017. Published by Elsevier B.V.)

The circadian clock controls a wide variety of metabolic and homeostatic processes in a number of tissues, including the kidney. However, the role of the renal circadian clocks remains largely unknown. To address this question, we performed a combined functional, transcriptomic, and metabolomic analysis in mice with inducible conditional knockout (cKO) of BMAL1, which is critically involved in the circadian clock system, in renal tubular cells (Bmal1 lox/lox /Pax8-rtTA/LC1 mice). Induction of cKO in adult mice did not produce obvious abnormalities in renal sodium, potassium, or water handling. Deep sequencing of the renal transcriptome revealed significant changes in the expression of genes related to metabolic pathways and organic anion transport in cKO mice compared with control littermates. Furthermore, kidneys from cKO mice exhibited a significant decrease in the NAD + -to-NADH ratio, which reflects the oxidative phosphorylation-to-glycolysis ratio and/or the status of mitochondrial function. Metabolome profiling showed significant changes in plasma levels of amino acids, biogenic amines, acylcarnitines, and lipids. In-depth analysis of two selected pathways revealed a significant increase in plasma urea level correlating with increased renal Arginase II activity, hyperargininemia, and increased kidney arginine content as well as a significant increase in plasma creatinine concentration and a reduced capacity of the kidney to secrete anionic drugs (furosemide) paralleled by an approximate 80% decrease in the expression level of organic anion transporter 3 (SLC22a8). Collectively, these results indicate that the renal circadian clocks control a variety of metabolic/homeostatic processes at the intrarenal and systemic levels and are involved in drug disposition., (Copyright © 2016 by the American Society of Nephrology.)

LCZ696 is a first-in-class angiotensin receptor neprilysin inhibitor in development for treatments of hypertension and heart failure indications. In 3 separate studies, pharmacokinetic drug-drug interactions (DDIs) potential was assessed when LCZ696 was coadministered with hydrochlorothiazide (HCTZ), amlodipine, or carvedilol. The studies used a open-label, single-sequence, 3-period, crossover design in healthy subjects. Blood samples were collected to determine the pharmacokinetic parameters of LCZ696 analytes (AHU377, LBQ657, and valsartan), HCTZ, amlodipine, or carvedilol (R[+]- and S[-]-carvedilol) for statistical analysis. When coadministered LCZ696 with HCTZ, the 90% CIs of the geometric mean ratios of AUCtau,ss of HCTZ and that of LBQ657 were within a 0.80-1.25 interval, whereas HCTZ Cmax,ss decreased by 26%, LBQ657 Cmax,ss increased by 19%, and the AUCtau,ss and Cmax,ss of valsartan increased by 14% and 16%, respectively. Pharmacokinetics of amlodipine, R(+)- and S(-)-carvedilol, or LBQ657 were not altered after coadministration of LCZ696 with amlodipine or carvedilol. Coadministration of LCZ696 400 mg once daily (qd) with HCTZ 25 mg qd, amlodipine 10 mg qd, or carvedilol 25 mg twice a day (bid) had no clinically relevant pharmacokinetic drug-drug interactions. LCZ696, HCTZ, amlodipine, and carvedilol were safe and well tolerated when given alone or concomitantly in the investigated studies., (© 2015, The American College of Clinical Pharmacology.)

Objectives: The aim of the present study was to compare the pharmacokinetic profiles between a new generic and a branded reference formulation of irbesartan/ hydrochlorothiazide FDC tablets, and to assess the bioequivalence of the two products in healthy Chinese male volunteers., Materials and Methods: 24 male healthy volunteers participated in the open-label, single-dose, randomized-sequence, 2-way crossover study. Eligible subjects were randomly assigned (1:1) to receive a single 300/12.5-mg dose of either the test or reference formulation followed by a 1-week washout. Blood samples were obtained before (0 hours) and 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 36, 48, and 72 hours after dosing. Plasma concentrations of irbesartan and hydrochlorothiazide were analyzed by two separate validated liquid chromatography/tandem mass spectrometric (LC-MS/MS) methods., Results: For irbesartan, the 90% confidence intervals (CIs) of AUC0-t, AUC0-∞, and Cmax were 103.27-116.71%, 105.01-121.47%, and 84.15-96.88%, respectively. For hydrochlorothiazide, the 90% CIs of AUC0-t, AUC0-∞, and Cmax were 96.11-109.02%, 95.15-107.35%, and 91.66-101.40%, respectively. A total of 3 mild AEs were reported in 3 subjects (12.5%)., Conclusion: In this study, a single dose (300/12.5-mg) of the test formulation of irbesartan and hydrochlorothiazide FDC tablet in fasting healthy Chinese male volunteers met WHO's and China's FDA regulatory criteria for assumption of bioequivalence to the reference formulation based on AUC and Cmax. Both formulations were well tolerated.

Bumetanide is increasingly being used for experimental treatment of brain disorders, including neonatal seizures, epilepsy, and autism, because the neuronal Na-K-Cl cotransporter NKCC1, which is inhibited by bumetanide, is implicated in the pathophysiology of such disorders. However, use of bumetanide for treatment of brain disorders is associated with problems, including poor brain penetration and systemic adverse effects such as diuresis, hypokalemic alkalosis, and hearing loss. The poor brain penetration is thought to be related to its high ionization rate and plasma protein binding, which restrict brain entry by passive diffusion, but more recently brain efflux transporters have been involved, too. Multidrug resistance protein 4 (MRP4), organic anion transporter 3 (OAT3) and organic anion transporting polypeptide 2 (OATP2) were suggested to mediate bumetanide brain efflux, but direct proof is lacking. Because MRP4, OAT3, and OATP2 can be inhibited by probenecid, we studied whether this drug alters brain levels of bumetanide in mice. Probenecid (50 mg/kg) significantly increased brain levels of bumetanide up to 3-fold; however, it also increased its plasma levels, so that the brain:plasma ratio (~0.015-0.02) was not altered. Probenecid markedly increased the plasma half-life of bumetanide, indicating reduced elimination of bumetanide most likely by inhibition of OAT-mediated transport of bumetanide in the kidney. However, the diuretic activity of bumetanide was not reduced by probenecid. In conclusion, our study demonstrates that the clinically available drug probenecid can be used to increase brain levels of bumetanide and decrease its elimination, which could have therapeutic potential in the treatment of brain disorders., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: The novel iron-based phosphate binder sucroferric oxyhydroxide is being investigated for the treatment of hyperphosphatemia. Patients with chronic kidney disease often have multiple comorbidities that may necessitate the daily use of several types of medication. Therefore, the potential pharmacokinetic drug-drug interactions between sucroferric oxyhydroxide and selected drugs commonly taken by dialysis patients were investigated., Methods: Five Phase I, single-center, open-label, randomized, three-period crossover studies in healthy volunteers investigated the effect of a single dose of sucroferric oxyhydroxide 1 g (based on iron content) on the pharmacokinetics of losartan 100 mg, furosemide 40 mg, omeprazole 40 mg, digoxin 0.5 mg and warfarin 10 mg. Pharmacokinetic parameters [including area under the plasma concentration-time curve (AUC) from time 0 extrapolated to infinite time (AUC0-∞) and from 0 to 24 h (AUC0-24)] for these drugs were determined: alone in the presence of food; with sucroferric oxyhydroxide in the presence of food; 2 h after food and sucroferric oxyhydroxide administration., Results: Systemic exposure based on AUC0-∞ for all drugs, and AUC0-24 for all drugs except omeprazole (for which AUC 0-8 h was measured), was unaffected to a clinically significant extent by the presence of sucroferric oxyhydroxide, irrespective of whether sucroferric oxyhydroxide was administered with the drug or 2 h earlier., Conclusions: There is a low risk of drug-drug interactions between sucroferric oxyhydroxide and losartan, furosemide, digoxin and warfarin. There is also a low risk of drug-drug interaction with omeprazole (based on AUC0-∞ values). Therefore, sucroferric oxyhydroxide may be administered concomitantly without the need to adjust the dosage regimens of these drugs.

A new, specific and sensitive reversed-phase high-performance liquid chromatography method was developed for the simultaneous determination of metolazone (MET) and losartan potassium (LOS). Good chromatographic separation was achieved within 6.0 min on a 150 × 4.6 mm i.d., 5 µm Waters, Ireland and ProDIGY 5 ODS 3 100 A column. A mobile phase containing a mixture of methanol and 0.02 M phosphate buffer (65:35, v/v) at pH 3.0 was used. The analysis was performed at a flow rate of 1 mL/min with fluorescence detection at 410 nm after excitation at 230 nm. Aspirin (ASP) was used as an internal standard. The proposed method was rectilinear over 2.0-40.0 (MET) and 40.0-800.0 ng/mL (LOS), with limits of detection of 0.22 and 4.52 ng/mL and limits of quantification of 0.68 and 13.70 ng/mL for MET and LOS, respectively. The method was successfully applied for the simultaneous analysis of the studied drugs in their laboratory-prepared mixtures, single tablets and co-formulated tablets. Moreover, the method was applied to an in vitro drug release (dissolution) test. The method was further extended to the determination of LOS in spiked human plasma. Statistical evaluation and comparison of data obtained using the proposed and comparison methods revealed no significant difference between the two methods in addition to good accuracy and precision for the proposed method., (Copyright © 2013 John Wiley & Sons, Ltd.)

Furosemide is a loop diuretic frequently used to treat fluid overload conditions such as hepatic cirrhosis and congestive heart failure (CHF). A population-based meta-analysis approach in NONMEM® was used to develop a PK model characterizing the time-course of furosemide in plasma and excretion into the urine for healthy subjects and fluid overload patients. Furosemide PK data from healthy subjects receiving 80 mg of oral furosemide were supplemented with additional individual and aggregate plasma concentration and urinary excretion versus time data from the literature after intravenous (i.v.) or oral furosemide administration (10-500 mg) to healthy subjects or fluid overload patients. A three-compartment model with zero-order input following i.v. administration (or first-order absorption using a Weibull function after oral administration) and first-order elimination best described furosemide PK. A covariate analysis identified creatinine clearance (CL(CR)) as a statistically significant predictor of renal clearance (CL(R)), with a population mean CL(R) of 4.67, 3.11, 1.95 and 1.17 l/h for a subject with normal renal function (CL(CR) = 120 ml/min) or mild (CL(CR) = 80 ml/min), moderate (CL(CR) = 50 ml/min) or severe (CLCR  = 30 ml/min) renal impairment. Oral bioavailability was 59.1% and non-renal clearance was 2.02 l/h. A PC-VPC and other model diagnostics demonstrated that the population PK model can reasonably predict the rate of urinary furosemide excretion over time using dosing history and commonly available demographic data, allowing for convenient assessment of PK-PD relationships for furosemide when given alone or in combination with other agents used to treat fluid overload conditions., (Copyright © 2013 John Wiley & Sons, Ltd.)

Hydrochlorothiazide (HCTZ) is a thiazide diuretic used for the treatment of hypertension and edema associated with fluid overload conditions such as congestive heart failure (CHF). A population-based meta-analysis approach in NONMEM® was used to develop a PK model to characterize the time-course of HCTZ concentrations in plasma and excretion into the urine for healthy subjects and CHF patients. Data from healthy subjects receiving 100 mg of oral HCTZ were supplemented with additional plasma concentration and urinary excretion versus time data published in the literature following administration of oral HCTZ doses ranging from 10 to 500 mg to healthy subjects or patients with renal failure, CHF or hypertension. A two-compartment model with first-order oral absorption, using a Weibull function, and first-order elimination best described HCTZ PK. Creatinine clearance (CLCR ) was a statistically significant predictor of renal clearance (CLR ). Non-renal clearance was estimated to be 2.44 l/h, CLR was 18.3 l/h and T1/2,α was 1.6 h and T1/2,β was 14.8 h for a typical individual with normal renal function (CLCR  = 120 ml/min). However, CLR was reduced to 10.5, 5.47 and 2.70 l/h in mild (CLCR  = 80 ml/min), moderate (CLCR  = 50 ml/min) and severe (CLCR  = 30 ml/min) renal impairment, respectively. Model diagnostics helped to demonstrate that the population PK model reasonably predicts the rate of urinary HCTZ excretion over time using dosing history and estimated CLCR , allowing for the convenient assessment of PK-PD relationships for HCTZ when given alone or in combination with other agents used to treat fluid overload conditions., (Copyright © 2013 John Wiley & Sons, Ltd.)

In this work, an electrogenerated chemiluminescence (ECL) detector with improved stability was developed for high-performance liquid chromatography (HPLC) detection of hydrochlorothiazide (HCTZ). The detector was prepared by packing cation exchanged resin particles in a glass tube, followed by inserting Pt wires (working electrode) in this tube and sealing. The leakage of Ru(bpy)3(2+) from the resin was compensated by adding a small amount of Ru(bpy)3(2+) in the mobile phase. Factors affected the performance of the proposed ECL detector were investigated. Under the optimal conditions, the ECL intensity has a linear relationship with the concentration of HCTZ in the range of 5.0 × 10(-8) g mL(-1)-2.5 × 10(-5) g mL(-1) and the detection limit was 2.0 × 10(-8) g mL(-1) (S/N=3). Application of the detector to the analysis of HCTZ in human serum proved feasible., (Copyright © 2013 Elsevier B.V. All rights reserved.)

At present the role of capillary electrophoresis in the detection of doping agents in athletes is, for the most part, nonexistent. More traditional techniques, namely gas and liquid chromatography with mass spectrometric detection, remain the gold standard of antidoping tests. This Feature will investigate the in-roads that capillary electrophoresis has made, the limitations that the technique suffers from, and where the technique may grow into being a key tool for antidoping analysis.

Ergosta-4,6,8(14),22-tetraen-3-one (ergone) isolated from Polyporus umbellatus possesses a variety of pharmacological activities in vivo and in vitro, including cytotoxic, diuretic, and immunosuppressive effect. The interaction of cerium ions (Ce(3+)) with ergone was studied by fluorescence and absorption spectroscopy. Spectra data revealed that Ce(3+) ions exhibited emission maxima around 350 nm when the excitation wavelength was fixed at 255 or 290 nm, and the fluorescence of Ce(3+) ions was quenched by the addition of ergone, indicating that a Ce(3+)-ergone complex was formed. According to the modified Benesi-Hildebrand equation, the binding constant of interaction of Ce(3+) ions with ergone was obtained at room temperature. Based on this, a sensitive spectrofluorometric method using Ce(3+) ions as a probe was applied for the identification and quantification of ergone in rat plasma, feces, and urine. The linear ranges of the calibration curves were 1.31 to 4.50 μM for plasma, 1.12-9.87 μM for feces, and 1.28-3.42 μM for urine, and the ergone recoveries were found to be 97.1 ± 0.9%, 98.2 ± 0.7% and 96.5 ± 1.4% for plasma, feces, and urine, respectively. The intraday and inter-day relative standard deviations were less than 9.7%. The proposed spectrofluorometric method is simple and rapid for the quantitative determination of ergone in rat plasma, feces, and urine, and it is affordable for most laboratories because it has few requirements and uses low cost, easy to operate equipment.

Purpose: To compare the pharmacokinetics and pharmacodynamics of tolvaptan in Caucasian and Japanese healthy male subjects under fasting and non-fasting conditions., Methods: This was a single-center, parallel-group, randomized, open-label, three-period crossover trial of single oral doses of tolvaptan 30 mg under fasting and non-fasting [a high-fat, high-calorie meal (HFM) or Japanese standard meal] conditions in 25 healthy male Caucasian subjects and 24 healthy male Japanese subjects. Pharmacodynamic endpoints were urine volume and fluid balance for 0 to 24 h postdose., Results: In the fasted state, the plasma tolvaptan C(max) and AUC(∞) geometric mean ratios (90 % confidence interval) were 1.105 (0.845-1.444) and 1.145 (0.843-1.554) for Japanese compared to Caucasian subjects. A HFM increased the C(max) and AUC(∞) values by about 1.15-fold in both Japanese and Caucasian subjects.. Twenty-four-hour urine volumes paralleled pharmacokinetic changes, but the increases were not clinically significant. Fluid balance in the Japanese men was 1.4- to 2.0-fold more negative than that in the Caucasian men., Conclusion: Tolvaptan pharmacokinetics is not clinically significantly affected by race. Body weight is a factor that affects exposure. Tolvaptan can be administered with or without food.

A rapid, selective and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay has been proposed for the determination of bumetanide in human plasma using tamsulosin as internal standard (IS). The analyte and IS were extracted from 200 μL of human plasma via solid phase extraction and the chromatographic separation was achieved on Peerless Basic C18 (100 mm × 4.6 mm, 3 μm) column under isocratic conditions. Detection of bumetanide and IS was done by tandem mass spectrometry, operating in positive ionization and multiple reaction monitoring (MRM) acquisition mode. The protonated precursor to product ion transitions monitored for bumetanide and IS were m/z 365.2→240.2 and 409.2→228.2 respectively. The method was fully validated as per the US FDA guidelines. The limit of detection and lower limit of quantitation of the method were 0.03 and 0.30 ng/mL respectively with a linear dynamic range of 0.30-200.0 ng/mL for bumetanide. The intra-batch and inter-batch precision (% CV) was ≤6.9% while the mean extraction recovery was >90% across quality control levels. The method is selective in presence of four diuretic drugs and some commonly used medications by healthy volunteers. It was successfully applied to a bioequivalence study of 2mg bumetanide tablet formulation in 10 healthy Indian male subjects under fasting condition. The reproducibility in the measurement of study data was demonstrated by reanalysis of 42 incurred samples., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A simple RP-HPLC method for the quantification of valsartan (VAL), amlodipine (AML) and hydrochlorothiazide (HCT) in human plasma was developed and validated. VAL, AML and HCT were resolved using a Gemini C18 column and mobile phase gradient starting from 20 % acetonitrile and 80 % 10 mmol L(-1) ammonium formate (V/V, pH 3.5 ± 0.2, by formic acid) to 70 % acetonitrile and 30 % 10 mmol L(-1) ammonium formate, over 20 minutes, with a flow rate of 1 mL min(-1). The samples were purified by protein precipitation and extraction. Telmisartan was used as internal standard. The method was validated according to USFDA and EMEA guidelines with good reproducibility and linear responses R = 0.9985 (VAL), 0.9964 (AML), and 0.9971 (HCT). RSDs of intra- and inter-day precision ranged 2.2-8.1 and 4.6-11.7 %, respectively, for all three drugs. Mean extraction recoveries of three QCs for the triple drug combination were 76.5 (VAL), 72.0 (AML) and 73.0 (HCT) % for human plasma. Although the LC-MS/MS method is more sensitive than HPLC, HPLC is still suitable for preliminary pharmacokinetic study. The experiments performed demostrated that simultaneous determination of all components of the triple drug combination in human plasma can be done by this method. Proposed method can be also used for guidance to the LC-MS/MS method.

Purpose: Tolvaptan is a selective vasopressin V2 receptor antagonist that can be given orally once daily for treatment of clinically significant hypervolemic and euvolemic hyponatremia (US and Europe) or extracellular volume expansion despite taking other diuretics (Japan). In vitro studies indicated that tolvaptan was a CYP3A4 substrate., Methods: A single-center, randomized, crossover trial of 60-mg tolvaptan with 240 mL of water or with 240 mL of reconstituted grapefruit juice (washout period of 72 h between doses) was conducted in 20 healthy subjects. Blood samples for tolvaptan plasma concentrations were obtained for 48 h postdose., Results: All subjects completed the trial. Following co-administration with grapefruit juice, tolvaptan concentrations were elevated compared with tolvaptan alone for only 16 h postdose; consequently, the mean elimination half-life of tolvaptan was unchanged, 5.7 vs 5.1 h respectively. The mean maximal plasma concentration (C(max)) and the area under the curve (AUC(∞)) of tolvaptan were increased 1.86- and 1.56-fold respectively when co-administered with grapefruit juice., Conclusions: It appears that grapefruit juice increases the bioavailability of tolvaptan, but does not affect its systemic elimination. The adverse event profile was consistent with the aquaretic effect of tolvaptan as urinary frequency, thirst, and dry mouth were the most frequently reported events.

Purpose: This study aimed to investigate the pharmacokinetics, pharmacodynamics, efficacy and safety of tolvaptan, an orally effective vasopressin V2-receptor antagonist., Methods: This was a multicenter, randomized, double-blind, parallel group study. Tolvaptan was administered at 7.5 or 15 mg, in combination with furosemide, for 7 days in Japanese heart failure (HF) patients with volume overload that had not resolved despite receiving furosemide., Results: The blood concentration of tolvaptan was maintained at a higher concentration for a longer time in patients who received 15 mg/day when compared with patients who received 7.5 mg/day. Tolvaptan increased urine volume and increased weight loss dose-dependently when used in combination with furosemide. Importantly, tolvaptan enhanced water diuresis without affecting blood electrolyte levels., Conclusion: Tolvaptan exerts diuretic effects and causes body weight loss at the low dose of 7.5 mg; however, these effects were less than those elicited by 15 mg tolvaptan.

Purpose: Single- and multiple-dose studies were conducted to assess the pharmacokinetics, pharmacodynamics and safety of tolvaptan in healthy Japanese subjects., Methods: All studies were single-center, randomized, placebo-controlled, single-blind or double-blind. In an ascending single-dose study, subjects were given a single oral dose of 15-120 mg tolvaptan or placebo. In multiple-dose studies, subjects were given 30, 60, 90 or 120 mg tolvaptan or placebo once daily for 7 days., Results: After a single dose of 15-120 mg tolvaptan, the maximum plasma concentration (C(max)) and the area under the plasma concentration-time curve from zero to time t (AUC(t)) increased dose-dependently, and increases in AUC(t) were dose-proportional. Increases in 24-hour cumulative urine volume were dose- and AUC(24hr)-dependent. Urine excretion rates reached a maximum within 2-4 h after dosing. The maximal urine excretion rates increased dose-dependently, and appeared to reach a plateau at doses ≥ 60 mg. A decrease in urine osmolality and an increase in free water clearance indicated an aquaretic effect of tolvaptan. Serum sodium concentrations were increased by tolvaptan and were higher than that with placebo, even 24 h after dosing, while serum potassium concentrations were unchanged. No tolvaptan accumulation was found after multiple dosing for 7 days. Although 24-hour cumulative urine volume following multiple dosing slightly decreased, a sustained diuretic effect was observed throughout the dosing period. The most common adverse event was mild thirst., Conclusions: Single and multiple oral doses of tolvaptan exhibited dose-dependent aquaretic effects. Tolvaptan was well tolerated at all doses tested.

Tonapofylline is an antagonist of adenosine A1 receptor being developed for heart failure. In the present studies, pharmacokinetic characteristics, including dose proportionality, bioavailability, and effects of gender and food, were evaluated in healthy subjects receiving single-dose tonapofylline (0.2-375 mg) in a parallel or crossover design. Following oral administration, tonapofylline concentrations mostly peaked within 3 hours and declined over time in a multiple phasic manner. Based on a power model, dose proportionality of peak concentration (C(max)), area under the time-concentration curve for all values (AUC(all)), and area under the time-concentration curve to infinity (AUC(inf)) was concluded in a clinical setting. The bioavailability of tonapofylline was 81.2% (90% confidence interval, 70.6%-93.5%). Following intravenous administration, the steady-state volume of distribution of tonapofylline was estimated to be 756 mL/kg. The total clearance of tonapofylline was low (64.8 mL/h/kg), approximately 5% of hepatic blood flow. The terminal half-life was variable within groups and ranged from 11.2 to 24.2 hours across the dose range. Female subjects showed significantly higher C(max), AUC(all), and AUC(inf) than male subjects (P < .05). Food decreased C(max) by approximately 39%, whereas it did not appear to affect AUC(all) and AUC(inf). The intersubject variability of the pharmacokinetic parameters of tonapofylline was generally less than 30%. In these studies, a single dose of tonapofylline was safe and well tolerated.

A tandem solid-phase extraction method (SPE) of connecting two different cartridges (C(18) and MCX) in series was developed as the extraction procedure in this article, which provided better extraction yields (>86%) for all analytes and more appropriate sample purification from endogenous interference materials compared with a single cartridge. Analyte separation was achieved on a C(18) reversed-phase column at the wavelength of 265 nm by high-performance liquid chromatography (HPLC). The method was validated in terms of extraction yield, precision and accuracy. These assays gave mean accuracy values higher than 89% with RSD values that were always less than 3.8%. The method has been successfully applied to plasma samples from rats after oral administration of target compounds., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Diuretics are drugs that increase the rate of urine flow and sodium excretion to adjust the volume and composition of body fluids. There are several major categories of this drug class and the compounds vary greatly in structure, physicochemical properties, effects on urinary composition and renal haemodynamics, and site and mechanism of action. Diuretics are often abused by athletes to excrete water for rapid weight loss and to mask the presence of other banned substances. Because of their abuse by athletes, diuretics have been included on The World Anti-Doping Agency's (WADA) list of prohibited substances; the use of diuretics is banned both in competition and out of competition and diuretics are routinely screened for by anti-doping laboratories. This review provides an overview of the pharmacology and toxicology of diuretics and discusses their application in sports. The most common analytical strategies currently followed by the anti-doping laboratories accredited by the WADA are discussed along with the challenges laboratories face for the analysis of this diverse class of drugs.

A sensitive, specific and selective liquid chromatography/tandem mass spectrometric method has been developed and validated for the simultaneous determination of irbesartan and hydrochlorothiazide in human plasma. Plasma samples were prepared using protein precipitation with acetonitrile, the two analytes and the internal standard losartan were separated on a reverse phase C(18) column (50mmx4mm, 3microm) using water with 2.5% formic acid, methanol and acetonitrile (40:45:15, v/v/v (%)) as a mobile phase (flow rate of 0.70mL/min). Irbesartan and hydrochlorothiazide were ionized using ESI source in negative ion mode, prior to detection by multiple reaction monitoring (MRM) mode while monitoring at the following transitions: m/z 296-->269 and m/z 296-->205 for hydrochlorothiazide, 427-->175 for irbesartan. Linearity was demonstrated over the concentration range 0.06-6.00microg/mL for irbesartan and 1.00-112.00ng/mL for hydrochlorothiazide. The developed and validated method was successfully applied to a bioequivalence study of irbesartan (300mg) with hydrochlorothiazide (12.5mg) tablet in healthy volunteers (N=36)., (Copyright 2009 Elsevier B.V. All rights reserved.)

Highly selective molecularly imprinted polymers (MIPs) for solid-phase extraction and determination of furosemide in human plasma have been designed and prepared. In order to study the intermolecular interactions in the pre-polymerization mixture and to find a suitable functional monomer in MIP preparation, a computational approach was developed. It was based on the comparison of the binding energy of the complexes between the template and functional monomers. Having confirmed the results of computational method, three MIPs were synthesized with different functional monomers, i.e. acrylamide (AAM), 4-vinylpiridine (4-VP) and acrylonitrile (ACN), and then evaluated using Langmuir-Freundlich (LF) isotherm. Using the MIP prepared by AAM as functional monomer, a molecularly imprinted solid-phase extraction procedure followed by high performance liquid chromatography with ultraviolet detector (MISPE-HPLC-UV) was developed for selective extraction and determination of furosemide in human plasma. For the proposed MISPE-HPLC-UV method, the linearity between responses (peak area) and concentration was found over the range of 75-3500 ng mL(-1) with a linear regression coefficient (R(2)) of 0.997. The limit of detection (LOD) and quantification (LOQ) in plasma were 12.9 and 43.3 ng mL(-1), respectively., (Copyright 2009 Elsevier B.V. All rights reserved.)

1. The main objective of the present study was to compare the bioavailability/bioequivalence of a new prolonged-release (PR) formulation of torasemide with an immediate-release (IR) formulation. In addition, we assessed the pharmacokinetics of both formulations, as well as the urine pharmacodynamics. 2. Two doses (5 and 10 mg) of PR torasemide were compared with the same doses of IR torasemide in a single-blind, single-dose, two-treatment, two-period, cross-over, sequence-randomized clinical trial in 20 healthy volunteers (two groups; n = 10 in each group). Torasemide plasma concentrations were measured by high-pressure liquid chromatography-electrospray ionization mass spectrometry. Torasemide urine concentrations, the diuretic effect of torasemide, urine electrolytes and urine density were also determined. 3. Plasma bioequivalence parameters, based on logged values, were as follows: (i) in the 5 mg group, the area under the plasma drug concentration-time curve from t = 0 to last measurable drug concentration at time t (AUC(0-t)) tablet ratio was 1.03 (90% confidence interval (CI) 0.91-1.17) and C(max) was 0.82 (90% CI: 0.68-0.98); and (ii) in the 10 mg group, the AUC(0-t) was 1.07 (90% CI 0.99-1.14) and C(max) was 0.68 (90% CI 0.60-0.78). The PR formulation showed a significantly prolonged t(max) compared with the IR formulation. The amount of torasemide recovered in the urine 24 h after administration was higher with the PR formulation for both doses. The natriuretic rate versus torasemide excretion rate for the PR and IR formulations were successfully regressed to a sigmoid E(max) model. Pharmacodynamic urine evaluations were similar with both formulations, although urine volume and urine electrolyte excretion were lower for the PR formulation in the first hour after administration. However, the PR formulation showed higher natriuretic efficiency. No significant adverse events were reported. 4. In conclusion, both formulations of torasemide showed similar systemic exposure (AUC). However, the PR formulation had a lower rate of absorption (lower C(max) and prolonged t(max)). The PR formulation had urinary excretion rates that were associated with a higher natriuretic efficiency and more constant diuresis.

A sensitive, selective and rapid liquid chromatography/tandem mass spectrometric (LC-MS/MS) method was developed and validated for the determination of hydrochlorothiazide (HCTZ) in human plasma. The plasma samples were prepared by solid phase extraction using Oasis HLB 30 mg 1CC cartridges. Chromatographic separation was accomplished on a Thermo Hypurity Advance (50 mm x 4.6mm i.d., 5 microm) column. The mobile phase consisted of HPLC Grade Acetonitrile: 2 mM Ammonium acetate (90 : 10 v / v) at a flow rate of 0.5 mL min(-1). Detection of hydrochlorothiazide and the internal standard (IS) zidovudine was achieved by ESI MS/MS in the negative ion mode. The total chromatographic runtime was 2.5 minutes. The linear range of the method was from 2.036-203.621 ng mL(-1). The mass transition ion pair has been followed as m/z 296.10/205.00 for HCTZ and 266.10/223.10 for Zidovudine. The mean overall recovery of HCTZ was 66.40% with a precision of 2.44%. The mean recovery of internal standard (Zidovudine) was 63.62% with a precision ranging from 2.06% to 5.40%. The method was successfully applied for the evaluation of pharmacokinetics of hydrochlorothiazide after single oral dose of 25 mg hydrochlorothiazide to healthy volunteers.

A rapid and sensitive method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been developed for the simultaneous determination of telmisartan and hydrochlorothiazide in human plasma. Sample preparation involved liquid-liquid extraction with diethyl ether-dichloromethane (60:40, v/v). The analytes and internal standard, probenecid, were separated on a Venusil XBP-C(8) column using gradient elution with acetonitrile-10 mM ammonium acetate-formic acid at a flow rate of 1.2 mL/min. Detection was by electrospray negative ionization mass spectrometry using multiple reaction monitoring of the transitions at m/z 513.0-->469.4 for telmisartan, m/z 295.9-->268.9 for hydrochlorothiazide and m/z 283.9-->239.9 for probenecid. For both analytes, the method was linear in the range 1.00-600 ng/mL with intra- and inter-day precision (as relative standard deviation)

Objectives: To document the diuretic effect of different oral doses of spironolactone (SP) in healthy dogs., Background: SP is currently mentioned as a diuretic agent in the dog. However, the recommended doses were empirically defined and their corresponding diuretic effect has never been documented in dogs., Animals, Materials and Methods: Eight adult Beagle dogs were used for two separate 2*2 cross-over designs. In the first cross-over, 4 dogs received SP orally for 8 days at 1 and 2mg/kg per day. In the second cross-over the 4 other dogs received SP similarly, but at 4 and 8 mg/kg per day. Dogs were weighed on the first and last day of each period. Plasma SP and canrenone (the main active metabolite of SP) were assayed by high performance liquid chromatography (HPLC). Daily water consumption, urine weight, urine specific gravity, and urine excretion of sodium and potassium were measured during the SP treatment., Results: Two hours after SP administration, SP was metabolized into canrenone. A significant 14 and 22% decrease in urine potassium excretion was observed at 1 and 2mg/kg, respectively, but not at the two other dose levels. Daily water consumption, urine weight, urine specific gravity, and urine excretion of sodium were not significantly altered by the SP treatment regardless of dose., Conclusions: Repeated oral administration of SP at 1, 2, 4 or 8 mg/kg for 8 days had no effect on water and sodium diuresis in healthy dogs.

In this study, a fast and sensitive liquid chromatography/tandem mass spectrometry method for determination of hydrochlorothiazide in human plasma was developed and validated. The analyte and irbesartan, used as the internal standard, were precipitated and extracted from plasma using methanol. Analysis was performed on a Phenomenex Kromasil C(8) column with water and methanol (27:73, v/v) as the mobile phase. Linearity was assessed from 0.78 to 200 ng/mL in plasma. The analytical method proved to be applicable in a pharmacokinetic study after oral administration of 12 mg hydrochlorothiazide tablets to 20 healthy volunteers.

The aim of our work was to develop an assay for the determination of proguanylin in human blood, and investigate its levels in healthy volunteers and donors suffer from hypertension often accompanied by body sodium accumulation and plasma volume expansion. We developed and evaluated the sandwich ELISA method for the quantitative determination of human proguanylin in serum samples. We conducted also the pilot study on individuals with hypertension and oh healthy probands and measured proguanylin serum levels, serum and urine sodium and creatinine levels. In the study on 256 healthy volunteers we demonstrated that women have significantly higher values of proguanylin than men (medians 12.7 vs. 9.6 ng/ml, p < 0.01) and proguanylin values increased with age of individuals (p < 0.01). Futhermore, we tested 17 individuals with hypertension and found that probands with anamnesi of hypertension had higher proguanylin values than healthy individuals from the first study (medians 16.2 vs. 11.3 ng/ml, p < 0.01). Both of groups did not differ in sex or age. Proguanylin values correlated with the systolic blood pressure (r = 0.41, p < 0.01), sodium fraction excretion (r = 0.72, p < 0.01) and serum sodium (r = -0.39, p < 0.01). No significant correlation we found with serum proguanylin and creatinine. In the group of 9 healthy probands we demonstrated the existence of a diurnal rhythm of proguanylin with its maximum in the evening hours (between 6-10 p.m.). The pilot study supports the hypothesis about the role of proguanylin in sodium metabolism and its possible importance for hypertension disorder. Further research is necessary to confirm our findings in individuals with hypertension with different medication in order to assess proguanylin value as a risk predictor of accelerated hypertension, and to classify individuals with hypertension for variuos types of diuretic therapy.

A new method for simultaneous determination of amiloride and hydrochlorothiazide by liquid chromatography/electrospray tandem mass spectrometry (LC/MS/MS) operated in positive and negative ionization switching mode was developed and validated. Protein precipitation with acetonitrile was selected for sample preparation. The analytes were separated on a Phenomenex Curosil-PFP (250x4.6 mm, 5 microm) column by a gradient elution with a mobile phase consisting of 0.15% formic acid solution containing 0.23% ammonium acetate and methanol pumped at a flow rate of 1.0 mL.min(-1). Rizatriptan was used as the internal standard (IS) for quantification. The determination was carried out on a Waters Quattro-micro triple-quadrupole mass spectrometer operated in multiple reaction monitoring (MRM) mode using the following transitions monitored simultaneously: positive m/z 230-->171 for amiloride, m/z 270-->158 for rizatriptan, and negative m/z 296-->205 for hydrochlorothiazide. The lower limits of quantification (LLOQs) were 0.1 and 1.0 ng.mL(-1) for amiloride and hydrochlorothiazide, respectively, which were lower than other published methods by using ultraviolet (UV), fluorimetric or mass spectrometric detection. The intra- and inter-day precision and accuracy were studied at three different concentration levels and were always better than 15% (n=5). This simple and robust LC/MS/MS method was successfully applied to the pharmacokinetic study of compound amiloride and hydrochlorothiazide tablets in healthy male Chinese volunteers., (Copyright (c) 2007 John Wiley & Sons, Ltd.)

Introduction: The objective of the present study was to explore a continuous intravenous furosemide regimen that adapts to urine output in neonates treated with extracorporeal membrane oxygenation (ECMO)., Methods: Seven neonates admitted to a paediatric surgical intensive care unit for ECMO therapy were treated with a furosemide regimen consisting of a loading bolus (1-2 mg/kg) followed by a continuous infusion at 0.2 mg/kg per hour, which was adjusted according to the target urine production of 6 ml/kg per hour. Therapeutic drug monitoring for furosemide concentrations in blood was performed., Results: The mean +/- standard deviation furosemide dose was 0.17 +/- 0.06 mg/kg per hour, 0.08 +/- 0.04 mg/kg per hour and 0.12 +/- 0.07 mg/kg per hour, respectively, on the first day, second day and third day of the study. The median (range of the urine production of the study subjects) urine production over the consecutive study days was 6.8 (0.8-8.4) mg/kg per hour, 6.0 (4.7-8.9) mg/kg per hour and 5.4 (3.4-10.1) ml/kg per hour. The target urine production was reached after a median time of 7 (3-37) hours. The regimen was haemodynamically well tolerated and the median furosemide serum concentration was 3.1 (0.4-12.9) mug/ml, well below the toxic level., Conclusion: The evaluated furosemide infusion appears an effective means to reduce volume overload in neonates treated with ECMO. The data of this preliminary study suggest that the starting dose of furosemide was too high, however, because the urine output was excessive and required frequent adaptations. The results of this study therefore indicate that a novel pharmacokinetic/pharmacodynamic model needs to be developed for neonates treated with ECMO.

In the present study we developed a fast and reliable HPLC assay for the determination of the loop diuretic furosemide in plasma and urine, using a Chromolith RP 18e (100 mm x 4.6 mm) monolithic silica rod HPLC column. After liquid-liquid extraction with diethylether plasma or urine samples were separated with a gradient consisting of solvent A (20% acetonitrile) and solvent B (80% acetonitrile), both in 0.25% acetic acid. The flow rate was 3.5 ml/min and the effluent was monitored by fluorescence with excitation at 230 nm and emission at 410 nm. The retention times for the internal standard (naproxen) and for furosemide were 2.1 and 3.7 min, respectively, and total run time was 8 min. The calibration curves were linear between 7.8 and 1000 ng/ml, and within-assay and between-assay coefficients of variation were <6.5% and <10%, respectively. The proposed assay for furosemide in plasma and urine using monolithic silica rod chromatography is fast, sensitive, and reliable, and, thus, well suited for pharmacokinetic studies.

This article describes reverse phase high-performance liquid chromatography (RPHPLC) methods for determination of diuretics in different human body fluids (whole blood, plasma, serum or urine). Sample preparation procedures, including solid-phase extraction, liquid-liquid extraction, dilution, precipitation as well as automated RPHPLC procedures, are discussed in order to present the advantages and disadvantages of each type of sample preparation. Also, values of analytical recovery of each procedure used for sample preparation are summarized. The most important RPHPLC parameters (detection mode, stationary phase, mobile phase, sensitivity, etc.) are also summarized and discussed.

A highly precise and sensitive method for the estimation of indapamide in human whole blood using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) is described. The method developed is validated in human whole-blood matrix, with a sensitivity of 0.5 ng/ml as lower limit of quantification. The procedure for the extraction of indapamide and glimepiride as internal standard (IS) involves haemolysis and deprotienation of whole blood using ZnSO(4) followed by liquid-liquid extraction using ethyl acetate. The sample extracts after drying were reconstituted and analysed by LC-MS/MS, equipped with turbo ion spray (TIS) source, operating in the positive ion and selective reaction monitoring (SRM) acquisition mode to quantify indapamide in human whole blood. The mean recovery for indapamide was 82.40 and 93.23% for IS. The total run time was 2.5 min to monitor both indapamide and the IS. The response of the LC-MS/MS method for indapamide was linear over the range of 0.5-80.0 ng/ml with correlation coefficient, r>or=0.9991. The coefficient of variance (% CV) at 0.5 ng/ml was 4.02% and the accuracy was well within the accepted limit of +/-20% at 0.5 ng/ml and +/-15% at all other concentrations in the linear range. This method is fully validated for the accuracy, precision and stability studies and also applied to subject-sample analysis of bioequivalence study for 1.5mg sustained-release (SR) formulations.