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Objectives/hypothesis: Oxymetazoline is an α-adrenergic agonist that is commonly used as a topical hemostatic agent in the operating room during ear, nose, and throat surgery. There are limited data on oxymetazoline pharmacokinetics in children who undergo general anesthesia. We assessed the hemodynamic effects and systemic absorption of topically applied oxymetazoline in children undergoing various nasal procedures., Study Design: Prospective trial., Methods: Children ages 2 to 17 years undergoing functional endoscopic sinus surgery, turbinate resection, or adenoidectomy were enrolled. The surgeon placed oxymetazoline-soaked pledgets (1.5 mL of 0.05% solution) according to our usual clinical practice. Blood samples for oxymetazoline assay were drawn at 5, 10, 20, 45, 90, and 150 minutes, and hemodynamic data were recorded at 5-minute intervals. Data analysis included mixed-effects regression and population pharmacokinetic/pharmacodynamic modeling., Results: The analysis included 27 patients, age 7 ± 4 years, who received between 2 and 12 pledgets (3-18 mL) of oxymetazoline. Relative bioavailability compared to the spray formulation was 2.3 (95% confidence interval [CI]: 1.6-3.2), with slow absorption from the mucosal surface (absorption half-life 64 minutes; 95% CI: 44-90). Mean arterial pressure did not increase with oxymetazoline instillation at the observed oxymetazoline serum concentrations (0.04-7.6 μg/L)., Conclusions: Despite concerns regarding oxymetazoline administration to mucosal membranes, we found that hemodynamic changes were clinically negligible with our usual clinical use of pledgets soaked in oxymetazoline. Compared to data on oxymetazoline in spray formulation, bioavailability was increased twofold with pledgets, but systemic absorption was very slow, contributing to low serum concentrations and limited hemodynamic effects., Level of Evidence: 1b. Laryngoscope, 129:2775-2781, 2019., (© 2019 The American Laryngological, Rhinological and Otological Society, Inc.)

Objective: To review and summarize topical oxymetazoline's pharmacology, pharmacokinetics, efficacy, safety, cost, and place in therapy for persistent redness associated with erythematotelangiectatic rosacea., Data Sources: Literature searches of MEDLINE (1975 to September 2017), International Pharmaceutical Abstracts (1975 to September 2017), and Cochrane Database (publications through September 2017) using the terms rosacea, persistent redness, α -agonist, and oxymetazoline., Study Selection and Data Extraction: Results were limited to studies of human subjects, English-language publications, and topical use of oxymetazoline. Relevant materials from government sources, industry, and reviews were also included., Data Synthesis: Data support the efficacy of oxymetazoline for persistent facial redness. Little study beyond clinical trials cited in the drug approval process has been conducted. Current data suggest that oxymetazoline is similar in safety and efficacy to brimonidine. Head-to-head comparisons of topical α-agonists for erythema caused by rosacea are needed., Conclusion: The topical α-agonist, oxymetazoline, is safe and effective for reducing persistent facial redness associated with erythematotelangiectatic subtype of rosacea. Health care practitioners selecting among treatments should consider not only the subtype of rosacea but also individual patient response, preference, and cost.

Vasoplegia is a ubiquitous phenomenon in all advanced shock states, including septic, cardiogenic, hemorrhagic, and anaphylactic shock. Its pathophysiology is complex, involving various mechanisms in vascular smooth muscle cells such as G protein-coupled receptor desensitization (adrenoceptors, vasopressin 1 receptors, angiotensin type 1 receptors), alteration of second messenger pathways, critical illness-related corticosteroid insufficiency, and increased production of nitric oxide. This review, based on a critical appraisal of the literature, discusses the main current treatments and future approaches. Our improved understanding of these mechanisms is progressively changing our therapeutic approach to vasoplegia from a standardized to a personalized multimodal treatment with the prescription of several vasopressors. While norepinephrine is confirmed as first line therapy for the treatment of vasoplegia, the latest Surviving Sepsis Campaign guidelines also consider that the best therapeutic management of vascular hyporesponsiveness to vasopressors could be a combination of multiple vasopressors, including norepinephrine and early prescription of vasopressin. This new approach is seemingly justified by the need to limit adrenoceptor desensitization as well as sympathetic overactivation given its subsequent deleterious impacts on hemodynamics and inflammation. Finally, based on new pathophysiological data, two potential drugs, selepressin and angiotensin II, are currently being evaluated.

Background: Oxymetazoline cream 1.0% is FDA-approved for the topical treatment of persistent facial erythema associated with rosacea in adults. This phase 2, multicenter, randomized, double-blind, parallel-group study assessed the pharmacokinetics, safety, and tolerability of oxymetazoline in patients with moderate to severe erythema associated with rosacea., Methods: Eligible patients were randomized to 1 of 8 treatment groups (oxymetazoline cream 0.5%, 1.0%, or 1.5% or vehicle applied topically either once or twice daily for 28 days). Pharmacokinetic analyses were conducted in patients receiving oxymetazoline. Plasma samples for pharmacokinetic assessments were collected prior to dosing and 6 times postdose on days 1 and 28., Results: A total of 356 patients were included in the safety population (oxymetazoline, n=268; vehicle, n=88). Thirty patients (11.2%) in the oxymetazoline group reported treatment-related treatment-emergent adverse events, most of which were mild to moderate application-site reactions. Oxymetazoline, at all concentrations, was generally safe and well tolerated. Mean maximum observed plasma concentrations were ≤115 pg/mL across all groups; the highest mean values for area under the plasma concentration-time curve from time 0 to 24 hours following once- and twice-daily administration of oxymetazoline 1.5% were 1680 pg•h/mL and 2660 pg•h/mL, respectively. Systemic exposure to oxymetazoline increased dose proportionally with once- and twice-daily administration., Conclusion: These findings support the use of oxymetazoline for the treatment of persistent facial erythema associated with rosacea. J Drugs Dermatol. 2018;17(2):213-220.

For this study, 31 compounds, including 16 imidazoline/α-adrenergic receptor (IRs/α-ARs) ligands and 15 central nervous system (CNS) drugs, were characterized in terms of the retention factors (k) obtained using biopartitioning micellar and classical reversed phase chromatography (log k BMC and log k wRP , respectively). Based on the retention factor (log k wRP ) and slope of the linear curve (S) the isocratic parameter (φ 0 ) was calculated. Obtained retention factors were correlated with experimental log BB values for the group of examined compounds. High correlations were obtained between logarithm of biopartitioning micellar chromatography (BMC) retention factor and effective permeability (r(log k BMC /log BB): 0.77), while for RP-HPLC system the correlations were lower (r(log k wRP /log BB): 0.58; r(S/log BB): -0.50; r(φ 0 /P e ): 0.61). Based on the log k BMC retention data and calculated molecular parameters of the examined compounds, quantitative structure-permeability relationship (QSPR) models were developed using partial least squares, stepwise multiple linear regression, support vector machine and artificial neural network methodologies. A high degree of structural diversity of the analysed IRs/α-ARs ligands and CNS drugs provides wide applicability domain of the QSPR models for estimation of blood-brain barrier penetration of the related compounds.

Objective: Midodrine is an α-agonist prodrug of desglymidodrine used for the management of hypotension, and can also be used for hepatorenal syndrome and cirrhotic patients with tense ascites. The objective of the present work was to study the clinical pharmacokinetic parameters of midodrine and its active metabolite desglymidodrine in cirrhotic patients with tense ascites, which may help in dose selection and improve treatment outcome., Method: This was a prospective, open-label, single-dose, parallel-group study. At first, a pilot study was performed on one healthy volunteer by taking serial blood samples at scheduled time intervals to validate the method of analysis and sampling times. The full study was then conducted by selecting 12 cirrhotic patients with tense ascites in one group and taking nine blood samples. We also selected five healthy volunteers as the control group and took 11 blood samples., Results: Statistically significant differences were observed between the healthy volunteer group and the patients group in the area under the concentration versus time curve (AUC0-t) and maximum plasma concentration (Cmax) values of midodrine and desglymidodrine. Based on the results of the pharmacokinetic analysis, the patient group was further subdivided into those receiving the interacting drug ranitidine (five patients) and those not receiving the interacting drug (seven patients)., Conclusions: Pharmacokinetic parameters of midodrine can differ significantly in cirrhotic patients with tense ascites from those in healthy individuals. Drug monitoring, dose adjustments, and drug-drug interactions should all be considered during therapy in this vulnerable patient group.

Unlabelled: Opioid and α2 -adrenoceptor agonists are potent analgesic drugs and their analgesic effects can synergize when co-administered. These supra-additive interactions are potentially beneficial clinically; by increasing efficacy and/or reducing the total drug required to produce sufficient pain relief, undesired side effects can be minimized. However, combination therapies of opioids and α2 -adrenoceptor agonists remain underutilized clinically, in spite of a large body of preclinical evidence describing their synergistic interaction. One possible obstacle to the translation of preclinical findings to clinical applications is a lack of understanding of the mechanisms underlying the synergistic interactions between these two drug classes. In this review, we provide a detailed overview of the interactions between different opioid and α2 -adrenoceptor agonist combinations in preclinical studies. These studies have identified the spinal cord as an important site of action of synergistic interactions, provided insights into which receptors mediate these interactions and explored downstream signalling events enabling synergy. It is now well documented that the activation of both μ and δ opioid receptors can produce synergy with α2 -adrenoceptor agonists and that α2 -adrenoceptor agonists can mediate synergy through either the α2A or the α2C adrenoceptor subtypes. Current hypotheses surrounding the cellular mechanisms mediating opioid-adrenoceptor synergy, including PKC signalling and receptor oligomerization, and the evidence supporting them are presented. Finally, the implications of these findings for clinical applications and drug discovery are discussed., Linked Articles: This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2., (© 2014 The British Pharmacological Society.)

Anaphylaxis is a rapid, systemic, often unanticipated, and potentially life-threatening immune reaction occurring after exposure to certain foreign substances. The main immunologic triggers include food, insect venom, and medications. Multiple immunologic pathways underlie anaphylaxis, but most involve immune activation and release of immunomodulators. Anaphylaxis can be difficult to recognize clinically, making differential diagnosis key. The incidence of anaphylaxis has at least doubled during the past few decades, and in the United States alone, an estimated 1500 fatalities are attributed to anaphylaxis annually. The increasing incidence and potentially life-threatening nature of anaphylaxis coupled with diagnostic challenges make appropriate and timely treatment critical. Epinephrine is universally recommended as the first-line therapy for anaphylaxis, and early treatment is critical to prevent a potentially fatal outcome. Despite the evidence and guideline recommendations supporting its use for anaphylaxis, epinephrine remains underused. Data indicate that antihistamines are more commonly used to treat patients with anaphylaxis. Although histamine is involved in anaphylaxis, treatment with antihistamines does not relieve or prevent all of the pathophysiological symptoms of anaphylaxis, including the more serious complications such as airway obstruction, hypotension, and shock. Additionally, antihistamines do not act as rapidly as epinephrine; maximal plasma concentrations are reached between 1 and 3 hours for antihistamines compared with < 10 minutes for intramuscular epinephrine injection. This demonstrates the need for improved approaches to educate physicians and patients regarding the appropriate treatment of anaphylaxis.

Unlabelled: In children, because of the dead volume of the central venous catheter (CVC) and the low flow rate of norepinephrine (NE) infusion, the delay between start-up and effective administration can be adversely long. A theoretical calculation enables to estimate the delay and variations of effective administration. However, numerous factors can hinder this theoretical approach. Herein, we measured via bench testing the actual delay and stability of NE administration kinetics. Using an assembly reproducing our currently-implemented catecholamine administration protocol, diluted NE (200 μg ml(-1)) was infused at an initial rate of 2 ml h(-1) (theoretically 6.67 μg min(-1)) for a period of 24 h. An assay measuring the amount of NE (μg) exiting the CVC was conducted by high-pressure liquid chromatography with colorimetric detection. The theoretical calculation of the delay in administered NE, taking into account a CVC dead volume of 0.3 ml, was 9 min. The measured percentage of the administered dose as a function of time in minutes (M) was M0-M3 (0 %), M3-M6 (0 %), M6-M9 (13 %), M9-M12 (28 %), M12-M15 (70 %), and M15-M18 (100 %) The amount of NE (μg) at fixed rate (2 ml h(-1)) was established at 6.9 ± 0.4 μg min(-1) during the 24 h., Conclusion: Continuous NE infusion via a CVC at low rate is stable. In children, because of CVC dead volume and low flow rate infusion, the delay in achieving intended dose delivery is significantly longer than that estimated by theoretical calculation. New modalities of initiation of catecholamine infusion adapted to the child are warranted.

Extralabel drug use for pain relief in the United States is regulated under the Animal Medicinal Drug Use Clarification Act. Agents that may provide analgesia in livestock include local anesthetics, nonsteroidal antiinflammatory drugs, opioids, α2-agonists, and N-methyl-d-aspartate receptor antagonists. The challenges associated with providing pain relief in food animals and the salient pharmacokinetic and pharmacodynamic features of the analgesic compounds that could potentially be used in livestock are reviewed. The potential use of novel agents such as bicarbonate, magnesium, ethanol, and gabapentin to augment analgesia is also discussed., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Aim: To determine if the addition of adrenaline, clonidine, or their combination altered the pharmacokinetic profile of levobupivacaine administered via the caudal epidural route in children., Methods: Children aged <18 years old scheduled to undergo sub-umbilical surgery were administered caudal levobupivacaine plain 2.5 mg · ml(-1) or with adjuvants adrenaline 5 mcg · ml(-1) or clonidine 2 mcg · ml(-1) or their combination. Covariate analysis included weight and postnatal age (PNA). Time-concentration profile analysis was undertaken using nonlinear mixed effects models. A one-compartment linear disposition model with first-order input and first-order elimination was used to describe the data. The effect of either clonidine or adrenaline on absorption was investigated using a scaling parameter (Fabs(CLON), Fabs(ADR)) applied to the absorption half-life (Tabs)., Results: There were 240 children (median weight 11.0, range 1.9-56.1 kg; median postnatal age 16.7, range 0.6-167.6 months). Absorption of levobupivacaine was faster when mixed with clonidine (Fabs(CLON) 0.60; 95%CI 0.44, 0.83) but slower when mixed with adrenaline (Fabs(ADR) 2.12; 95%CI 1.45, 3.08). The addition of adrenaline to levobupivacaine resulted in a bifid absorption pattern. While initial absorption was unchanged (Tabs 0.15 h 95%CI 0.12, 0.18 h), there was a late absorption peak characterized by a Tabs(LATE) 2.34 h (95%CI 1.44, 4.97 h). The additional use of clonidine with adrenaline had minimal effect on the bifid absorption profile observed with adrenaline alone. Neither clonidine nor adrenaline had any effect on clearance. The population parameter estimate for volume of distribution was 157 l 70 kg(-1). Clearance was 6.5 l · h(-1) 70 kg(-1) at 1-month PNA and increased with a maturation half-time of 1.6 months to reach 90% of the mature value (18.5 l · h(-1) 70 kg(-1)) by 5 months PNA., Conclusions: The addition of adrenaline decreases the rate of levobupivacaine systemic absorption, reducing peak concentration by half. Levobupivacaine concentrations with adrenaline adjuvant were reduced compared to plain levobupivacaine for up to 3.5 hours. Clonidine as an adjuvant results in faster systemic absorption of levobupivacaine and similar concentration time profile to levobupivacaine alone. Adding adrenaline with clonidine does not alter the concentration profile observed with adrenaline alone., (© 2012 Blackwell Publishing Ltd.)

Attention-deficit/hyperactivity disorder (ADHD) is a common neurobehavioral disorder characterized by developmentally inappropriate levels of inattention, hyperactivity and impulsivity. Although much evidence supports the use of psychostimulants as a first-line treatment in children and adolescents, up to 30% of patients may have an inadequate response to these medications. For these patients, addition of an α₂-adrenoceptor agonist can further improve ADHD symptoms. The α₂-adrenoceptor agonists may work in a synergistic fashion with stimulants through regulation of prefrontal cortex function. Early studies were completed with immediate-release clonidine (CLON-IR), which requires multiple daily doses and achieves a higher maximum concentration more rapidly than the more recently developed extended-release clonidine (CLON-XR). Pharmacokinetic properties of CLON-XR may be responsible for differences in efficacy and tolerability between the CLON-IR and CLON-XR formulations. Recent double-blind, placebo-controlled trials have shown that extended-release α₂-adrenoceptor agonists are safe and effective, both as monotherapy and as adjunctive treatment with stimulants. This review will focus on clonidine used in conjunction with stimulants to optimize treatment of ADHD., (Copyright 2012 Prous Science, S.A.U. or its licensors. All rights reserved.)

More than 200 studies and reports have been published regarding the use of dexmedetomidine in infants and children. We reviewed the English literature to summarize the current state of knowledge of this drug in children for the practicing anesthesiologist. Dexmedetomidine is an effective sedative for infants and children that only minimally depresses the respiratory system while maintaining a patent airway. However, dexmedetomidine does depress the cardiovascular system. Specifically, bradycardia, hypotension, and hypertension occur to varying degrees depending on the age of the child. Hypertension is more prevalent when larger doses of dexmedetomidine are given to infants. Consistent with its 2-hour elimination half-life, recovery after dexmedetomidine may be protracted in comparison with other sedatives. Dexmedetomidine provides and augments analgesia and diminishes shivering as well as agitation postoperatively. The safety record of dexmedetomidine suggests that it can be used effectively and safely in children, with appropriate monitoring and interventions to manage cardiovascular sequelae.

Synephrine is a natural compound, frequently added to ephedra-free dietary supplements for weight-loss, due to its effects as a nonspecific adrenergic agonist. Though only p-synephrine has been documented in plants, the presence of m-synephrine has also been reported in weight-loss products. The use of synephrine in dietary supplements was accompanied by reports of adverse effects, especially at the cardiovascular level. It is well known that the imbalance in cardiac glutathione levels can increase the risk of cardiomyopathy. The present work aimed to study the role of organic cation-mediated transport of m- and p-synephrine and the possibility that p- and m-synephrine induce intracellular changes in glutathione levels in calcium-tolerant freshly isolated cardiomyocytes from adult rat. After a 3 h incubation with 1 mM p- or m-synephrine, the intracellular content of synephrine was measured by gas chromatography/ion trap-mass spectrometry (GC/IT-MS); cell viability and intracellular glutathione levels were also determined. To evaluate the potential protective effects of antioxidants against the adverse effects elicited by m-synephrine, cells were pre-incubated for 30 min with Tiron (100 μM) or N-acetyl-cysteine (NAC) (1 mM). To assess the influence of α(1)-adrenoceptors activation in glutathione depletion, a study with prazosin (100 nM) was also performed. The results obtained provide evidence that organic cation transporters OCT3 and OCT1 play a major role in m- and p-synephrine-mediated transport into the cardiomyocytes. The importance of these transporters seems similar for both isomers, although p-synephrine enters more into the cardiomyocytes. Furthermore, only m-synephrine induced intracellular total glutathione (GSHt) and reduced glutathione (GSH) depletion. NAC and Tiron were able to counteract the m-synephrine-induced GSH and GSHt decrease. On the other hand, the incubation with prazosin was not able to change m-synephrine-induced glutathione depletion showing that this effect is independent of α(1)-adrenoceptor stimulation. In conclusion, both positional isomers require OCT3 and OCT1-mediated transport to enter into the cardiomyocytes; however, the hydroxyl group in the p-position favours the OCT-mediated transport into cardiomyocytes. Furthermore, the structural isomerization of synephrine influences its toxicological profile since only m-synephrine caused GSH depletion.

Background: Oral clonidine is used as premedication in children. The bioavailability of clonidine given orally in adults is 75-100% but is unknown in children., Methods: Children (3-10 years) undergoing adenotonsillectomy were administered oral clonidine 4 mcg·kg(-1) mixed with apple fruit drink as premedication. Intravenous plasma was assayed for clonidine concentration at 5, 15, 30, 45 min and 1, 2, 4, 6, 12, 18 h after administration. Clonidine plasma concentrations were determined by liquid chromatography-mass spectroscopy, and pharmacokinetic parameters were calculated using nonlinear effects mixed-effects models. Current data were pooled with published time-concentration profiles from children (n = 49) administered intravenous clonidine to determine oral bioavailability., Results: There were eight children studied (age 3-10 years, weight 10.5-36 kg). A two-compartment model with first-order absorption and elimination was used to describe time-concentration profiles. Population parameter estimates (CV%; 95% CI), standardized to a 70-kg person, were absorption half-life (Tabs), 0.45 (85.1; 0.221-0.884) h, absorption lag time (Tlag), 0.148 (91.2; 0.002-0.316) h, Clearance (CL) 17.9 (30.3; 16-20.3) l·h(-1) per 70 kg, between compartment clearance (Q) 121 (44.3; 80.1-165) l·h(-1) per 70 kg, central volume (V1) 81.2 (71.5; 60.7-105) l·70 kg(-1), peripheral volume of distribution (V2) 113 (33.9; 91-131) l·70 kg(-1). The oral bioavailability was 55.4% (CV 6.4%; 95% CI 0.469, 0.654)., Conclusions: Clonidine administered with an apple fruit drink displays a variable and relatively slow absorption after oral administration (T(max) 1.04 h, C(max) 0.77 mcg·l(-1)). The oral bioavailability was 55.4%, which is less than reported in adults. Consequently, higher oral doses of clonidine (per kg) are required when this formulation is used to achieve concentrations similar to those reported in adults., (© 2010 Blackwell Publishing Ltd.)

Clonidine is a centrally acting, alpha-2 adrenergic agonist used for the treatment of hypertension during pregnancy. The metabolic pathways of clonidine are poorly understood, and the quantitative contribution of specific human cytochrome P450 (P450) isoforms has not been systematically assessed. In this study, 17 cDNA-expressed P450 enzymes, in addition to pooled human liver microsomes, were evaluated for clonidine 4-hydroxylation activity in vitro. Five P450 enzymes-CYP2D6, 1A2, 3A4, 1A1, and 3A5-catalyzed measurable formation of 4-hydroxyclonidine. Selective inhibition studies in human liver microsomes confirmed that these isoforms are jointly responsible for 4-hydroxylation of clonidine in vitro, and CYP2D6 accounted for approximately two-thirds of the activity. The major role of CYP2D6 in clonidine metabolism might explain the increase in its nonrenal clearance during pregnancy.

Unlabelled: Dysfunction of the sympathetic nervous system underlies many cardiac diseases and can be assessed by molecular imaging using PET in humans. Small-animal PET should enable noninvasive quantitation of the sympathetic nervous system in mouse models of human disease. For mice, however, the radioactivity needed to give acceptable image quality may be associated with a mass of unlabeled compound sufficient to block the binding of radioligand to its target. The present study assesses the feasibility of using [N-methyl-(11)C]meta-hydroxyephedrine ((11)C-mHED) to measure norepinephrine reuptake in humans, to determine cardiac innervation in mice., Methods: Anesthetized mice were placed in a small-animal PET scanner. (11)C-mHED (containing 18% precursor metaraminol) was injected via a tail vein into each animal simultaneously. Fifteen minutes later, animals were injected with saline or metaraminol which competes with mHED for norepinephrine reuptake. (18)F-FDG was injected at 60 min to identify heart regions. After reconstruction of the list-mode data, radioactivity in myocardial regions was computed using in-house software, and time-activity curves were plotted., Results: Hearts were clearly visualized after injection of (11)C-mHED. Injection of metaraminol at doses less than 50 nmol x kg(-1) had no effect, whereas doses greater than 100 nmol x kg(-1) caused a dose-dependent loss of specifically bound radioactivity., Conclusion: (11)C-mHED was successfully used to visualize and assess myocardial innervation in mice. Uptake of (11)C-mHED is displaceable by the false transmitter metaraminol. The total molar dose of metaraminol and (11)C-mHED must be considered in the analysis of PET data.

Medetomidine is a potent and selective alpha2-adrenergic agonist. The activation of alpha2-adrenergic receptor mediates a variety of effects including sedation, analgesia, relief of anxiety, vasoconstriction and bradycardia. However, our main interest is the sedative effects of medetomidine when used as a premedicant prior surgery in companion animals, especially in dogs. Recently, data suggested that following intravenous infusion at six dosing regiments non-linear pharmacokinetics was observed. Major causes of non-linear pharmacokinetics are the elimination of the drug not following a simple first-order kinetics and/or the elimination half-life changing due to saturation of an enzyme system. The goal of this study was to establish the metabolic stability and determine the metabolic pathway of medetomidine in dog liver microsomes. Consequently, Michaelis-Menten parameters (V(max), K(m)), T(1/2) and CL(i) were determined. The incubations were performed in a microcentrifuge tube and containing various concentrations of medetomidine (10-5000 nM), 1 mg/mL of microsomal proteins suspended in 0.1 M phosphate buffer, pH 7.4. Microsomal suspensions were preincubated with NADPH (1 mM) for 5 min at 37 degrees C prior to fortification with medetomidine. Samples were taken at various time points for kinetic information and the initial velocity (v(i)) was determined after 10 min incubation. The reaction was stopped by the addition of an internal standard solution (100 ng/mL of dextrometorphan in acetone). Medetomidine concentrations were determined using a selective and sensitive HPLC-ESI/MS/MS method. Using non-linear regression, we determined a K(m) value of 577 nM, indicating relatively low threshold enzyme saturation consistent with previous in vivo observation. The metabolic stability was determined at a concentration of 100 nm (<

Importance of the Field: Brimonidine is a drug used in the management of glaucoma throughout the world and is the most modern alpha(2)-adrenoceptor agonist available. This review comprehensively discusses the use of brimonidine for glaucoma., Areas Covered in This Review: A historical insight into the development of selective adrenergic glaucoma drugs is given, followed by a description of the mechanisms of action and a discussion of the main clinical trials investigating clinical applications. The safety of brimonidine is evaluated, and our expert opinion is provided on how brimonidine is used in our clinical practice. The most relevant literature on the role of brimonidine in glaucoma is discussed., What the Reader Will Gain: A clear understanding of the role of brimonidine for glaucoma treatment, with an explanation of its efficacy, limitations and use in clinical practice., Take Home Message: Brimonidine is an effective drug for lowering intraocular pressure. It has potentially serious systemic effects in children, in whom it is contraindicated. Its use in adults is limited by its ocular side effects such as allergy. Brimonidine is, however, an important part of the range of intraocular pressure lowering drugs available to prescribers.

This study investigated the differences in pharmacokinetic, urodynamic and haemodynamic parameters after administration of two dosages of phenylpropanolamine (PPA) in female Beagle dogs. Blood was collected and urethral pressure profiles were performed over 24 h periods following single or three times daily (T(0),T(6h),T(12h)) administration of PPA. The maximal concentration (C(max)) was reached 2 h after PPA administration (T(max)) and the half-life (T((1/2))) was 4 h. Three times daily administration induced an increase in C(max) due to bioaccumulation. A significant increase in urethral resistance, compared to the control group, was observed at T(max) after 1 week of once daily administrations, but not when PPA was administered every 6 h during the day, despite higher plasma concentrations following more frequent dosing. An increase in mean arterial pressure was compensated by a decreased heart rate. Clinical efficacy with the temporary increase in urethral resistance following single daily administration of PPA in dogs suffering from urethral sphincter mechanism incompetence (USMI) needs to be further investigated in a randomised clinical trial., (Copyright 2009 Elsevier Ltd. All rights reserved.)

Importance of the Field: The emergence of fixed-combination drugs for the treatment of glaucoma has, to some extent, changed the medical management of glaucoma. The potential benefits of these drugs include a reduction in the total number of drops and preservatives instilled per day and improved patient comfort factors, which may contribute to better compliance. Combination medications may also improve therapeutic efficacy and play an important role in controlling medication cost. However, the fixed dosing may be a disadvantage in some cases., Area Covered in This Review: This review describes the composition, pharmacokinetics, mode of action, efficacy, side effects, and safety profile of fixed-combination dorzolamide-timolol and fixed-combination brimonidine-timolol., What the Reader Will Gain: Understanding of the pros, cons, and safety profile of two FDA approved fixed-combination antiglaucoma medication., Take Home Message: Fixed-combination medications may be a reasonable adjunct to prostaglandins if a large drop in the intraocular pressure (IOP) is desired and adding only one medication is unlikely to reach the target IOP range. Both mentioned drugs are effective in reducing the IOP and further clinical studies will help identify differences in efficacy between the two. The clinician must make an individualized assessment of the medication's risk-benefit profile for each patient.

Alpha-methyldopa is a regularly used antihypertensive drug during pregnancy. Methyldopa, which decreases the sympathoadrenal system, is the first drug of choice since decades. The reactive hepatitis is not frequent, but known serious side effect of alpha-methyldopa. In non-pregnant women the estimated rate of manifest hepatotoxicity is 2.5-10%. In our case, gestation hypertension developed at the 21st gestation week of a 35 year-old pregnant woman. Oral methyldopa, a central alpha adrenergic blocker therapy was introduced. On the 23rd gestation week acute hepatitis developed. During differential diagnosis of hepatitis, the etiology of methyldopa was taken into account. Viral and autoimmune origin was rolled out. No fetal aberration was found during ultrasound examination. The function of drug metabolizing function from blood was measured by CYP phenotyping (CYP gene expression analysis). CYP3A4 enzyme plays a primary role in the metabolism of nifedipine. Antihypertensive therapy was changed from methyldopa to nifedipine. Nifedipine dosage was based on the value of CYP3A4 gene expression. With the reduced nifedipine therapy (30 mg daily), blood pressure was successfully under control. The diagnosis of alpha-methyldopa induced hepatitis was based on anamnesis, clinical picture and the results of chemical and radiological examination and confirmed by the level of drug-metabolizing capacity. The gestation hepatotoxicity of alpha-methyldopa was reported first in 1969 by Elkington Smith, who suggested the monitoring of serum aminotransferase during alpha-methyldopa therapy in pregnancy in their case report. Our case report confirms that monitoring of serum aminotransferase level is still valuable when treating a pregnant woman with alpha-methyldopa.

Background and Objective: The purpose of the present study was to compare the bioavailability of a new methyldopa (CAS 555-30-6) tablet formulation with that of a reference formulation in 12 healthy male subjects using a modified HPLC method., Methods: The study was designed as an open label, single-dose, randomized study with a cross-over design. Under fasting conditions, each subject received one 250-mg tablet orally as a single dose of a test or reference formulation on two treatment days. The treatment periods were separated by a one-week washout period. The blood samples were collected at different time points after each administration and determined using a rapid and reliable modified HPLC method. The method used was validated for specificity, accuracy, precision and sensitivity. The pharmacokinetic parameters (Cmax, AUC0-t, AUC0-infinity) were statistically compared by analysis of variance (ANOVA) for test and reference formulations., Results and Discussion: All validation criteria for the developed HPLC method were in acceptable range. The maximum plasma concentration (Cmax) of alpha-methyldopa was 270.3-1864.9 ng/ml for the test and 224.5-1585.6 ng/ml for the reference formulation. The mean AUC0-infinity of alpha-methyldopa was 2002.1-10614.8 and 2076.8- 9056.3 ng x h/ml for the test and reference formulation, respectively. The calculated 90% confidence intervals for the mean test/reference ratios of mentioned parameters were 92.48-115.94, and 88.82-101.13 which are in the bioequivalence range. The statistical tests did not show any statistical differences between formulations suggesting that methyldopa tablet of test and reference can be considered as bioequivalent preparations., Conclusion: A rapid and reliable HPLC method with fluorescence detector was developed to analyze alpha-methyldopa in human plasma. Based on the obtained results the test formulation of alpha-methyldopa is bioequivalent to the reference formulation.

The present experiments compared the peripheral and central pharmacological effects of three alpha(2)-adrenoceptor agonists: fadolmidine, clonidine, and dexmedetomidine after single intrathecal bolus injections at analgesic dose level in rats. Effects on mydriasis and cardiovascular functions were studied in anaesthetised rats, the effects on sedation/motor performance, body temperature, and gastrointestinal motility were evaluated in conscious rats, and also the effects on brain biogenic amines were studied. All compounds caused dose-dependent mydriasis, a decrease in blood pressure and heart rate, sedation, hypothermia, and inhibition of gastrointestinal transit, but in contrast to the analgesic effects, dexmedetomidine and clonidine were much more potent than fadolmidine. In accordance with the other systemic effects, dexmedetomidine and clonidine, but not fadolmidine, reduced the turnover of the monoamine neurotransmitters, noradrenaline and serotonin, in brain at the analgesic dose. The difference in the systemic effect profile between fadolmidine and clonidine or dexmedetomidine is most probably explained by differences in their ability to spread from the site of administration at the lumbar level into the periphery and/or the brain and further the concentrations of the compounds in the side of action. These results supports that intrathecally administered fadolmidine could have potential to be used as an analgesic agent with less subraspinal or spinal adverse effects at analgesic doses than dexmedetomidine and clonidine.

Background: Silodosin is a new alpha(1)-adrenergic receptor antagonist that is selective for the alpha(1A)-adrenergic receptor. It was approved by the US Food and Drug Administration (FDA) in 2008 for the treatment of lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH)., Objective: This article reviews the pharmacology, pharmacokinetics, clinical efficacy, adverse effects, drug interactions, and dosage and administration of silodosin in adult male patients with BPH., Methods: A search of MEDLINE (1950-October 8, 2009), International Pharmaceutical Abstracts (1970-October 8, 2009), and the Iowa Drug Information Service database (1966-October 8, 2009) was conducted using the terms silodosin, KMD-3213, benign prostatic hyperplasia, and alpha(1)-adrenergic receptor antagonist. Reports of research and review articles published in English were identified and evaluated, and the bibliographies of these articles were reviewed for additional relevant publications. A search of the FDA Web site was performed, and abstracts and posters presented at scientific meetings of the American Urological Association were reviewed., Results: By antagonizing alpha(1A)-adrenergic receptors in the prostate and urethra, silodosin causes smooth muscle relaxation in the LUT. Silodosin has greater affinity for the alpha(1A)-adrenergic receptor than for the alpha(1B)-adrenergic receptor (by a factor of 583), minimizing the propensity for blood pressure-related adverse effects mediated by alpha(1B) blockade. In 3 controlled clinical studies in patients with BPH-related LUTS (1 published; 2 presented in the prescribing information and published in a pooled analysis), patients receiving silodosin at a total daily dose of 8 mg had significant improvements in the International Prostate Symptom Score (IPSS) and maximum urinary flow rate (Q(max)) compared with those receiving placebo (both, P < 0.05). The most commonly reported adverse effect was abnormal or retrograde ejaculation (>22%), and the incidence of orthostatic hypotension was low (<3%)., Conclusions: In the small number of clinical trials reviewed, silodosin was associated with significant reductions in IPSS and Q(max) compared with placebo. To determine whether silodosin's selectivity for the alpha(1A)-adrenergic receptor translates into a clinical advantage relative to other available agents, long-term studies evaluating the comparative efficacy and tolerability of silodosin and other alpha(1)-blockers (specifically tamsulosin) are necessary., (Copyright 2009 Excerpta Medica Inc. All rights reserved.)

Background: Published dexmedetomidine pharmacokinetic studies in children are limited by participant numbers and restricted pathology. Pooling the available studies allows investigation of covariate effects., Methods: Data from four studies investigating dexmedetomidine pharmacokinetics after i.v. administration (n = 95) were combined to undertake a population pharmacokinetic analysis of dexmedetomidine time-concentration profiles (730 observations) using nonlinear mixed effects modeling (NONMEM). Estimates were standardized to a 70-kg adult using allometric size models., Results: Children had a mean age of 3.8 (median 3 years, range 1 week-14 years) and weight of 16.0 kg (median 13.3 kg, range 3.1-58.9 kg). Population parameter estimates (between subject variability) for a two-compartment model were clearance (CL) 42.1 (CV 30.9%) lx h(-1) x 70 kg(-1), central volume of distribution (V1) 56.3 (61.3%) l.70 kg(-1), inter-compartment clearance (Q) 78.3 (37.0%) l x h(-1) x 70 kg(-1) and peripheral volume of distribution (V2) 69.0 (47.0%) l.70 kg(-1). Clearance maturation with age was described using the Hill equation. Clearance increases from 18.2 l x h(-1) x 70 kg(-1) at birth in a term neonate to reach 84.5% of the mature value by 1 year of age. Children given infusion after cardiac surgery had 27% reduced clearance compared to a population given bolus dose. Simulation of published infusion rates that provide adequate sedation for intensive care patients found a target therapeutic concentration of between 0.4 and 0.8 microg x l(-1)., Conclusions: The sedation target concentration is similar to that described for adults. Immature clearance in the first year of life and a higher clearance (when expressed as l x h(-1) x kg(-1)) in small children dictate infusion rates that change with age. Extrapolation of dose from children given infusion in intensive care after cardiac surgery may not be applicable to those sedated for noninvasive procedures out of intensive care.

Twenty-three hours after heart transplantation, life-threatening acute right heart failure was diagnosed in a patient requiring continuous venovenous hemodiafiltration (CVVHDF). Increasing doses of catecholamines, sedatives, and muscle relaxants administered through a central venous catheter were ineffective. However, a bolus of epinephrine injected through an alternative catheter provoked a hypertensive crisis. Thus, interference with the central venous infusion by the dialysis catheter was suspected. The catheters were changed, and hemodynamics stabilized at lower catecholamine doses. When the effects of IV drugs are inadequate in patients receiving CVVHDF, interference with adjacent catheters resulting in elimination of the drug by CVVHDF should be suspected.

Clonidine is classified as an imidazoline and it is the prototypical alpha-2 receptor agonists. It has been used for several years to treat hypertension. It has also been used, "off label", for a variety of purposes, including opioid and anesthetic sparing effects, anxiolysis and sedation, drug withdrawal as well as stabilizing blood pressure and reducing stress response to surgery. Particularly in the case of patients with overt or underlying cardiac disease and in those at risk of perioperative ischemia the action of clonidine can be expected to reduce the risk of procedure-related cardiac events. In addition, clonidine used as a premedication drug before surgery or surgical procedure, has been shown to substantially reduce anaesthetic, benzodiazepine and opioids requirements. However, its "off label" use, the absence of an intravenous form of in the United States, possible inadvertent hypotension, bradycardia or post-operative sedation, and the variability of the haemodynamic response to different doses or rates of administration, have limited its use in clinical practice. This review discusses the potential role of clonidine and the supporting evidence for the use of this drug beyond its anti-hypertensive use in perioperative medicine and critical care in adults patients.

Background: The aim of this study was to investigate the uptake and release kinetics of two common glaucoma drugs delivered onto hydrogel contact lenses using analytical chemistry and to evaluate this device's ability to control intraocular pressure in a limited number of volunteers., Methods: Contact lenses were incubated in a source solution containing timolol maleate or brimonidine tartrate to determine uptake kinetics. The lenses were then immersed in fresh saline to determine release kinetics. Analysis was performed by high-pressure liquid chromatography (HPLC). HPLC column retention times were determined for drugs released from the lens individually and under co-elution conditions. To evaluate clinical feasibility and toxicity, three volunteers (patients being treated for glaucoma) were provided with contact lenses that had been passively impregnated with either drug. After a three-week wash-out period, the volunteers were instructed to wear the lenses for 30 minutes per day for two weeks., Results: HPLC analysis showed that maximum uptake and release of both drugs had occurred by approximately 60 minutes, with the slopes tending to flatten after this point. The retention time on the HPLC column was 8.08 minutes for timolol maleate and 2.16 minutes for brimonidine tartrate after incubation for one hour, with no changes after seven hours. Patient data showed that use of the lenses maintained IOP at levels equivalent to those obtained with previous treatment. No ocular toxicity was observed., Conclusion: Drugs commonly used for glaucoma treatment can be passively transferred to a hydrogel contact lens and then eluted from the polymer. Data obtained from a limited number of patients suggest that this contact lens/drug delivery system may be a feasible means of controlling IOP.

Objective: To review the available evidence for the neuroprotective qualities of brimonidine tartrate in optic nerve and retinal injury., Methods: References for this study were obtained by running a search of the PubMed database using keywords brimonidine, neuroprotection, ischemic optic neuropathy, and alpha2-adrenergic agonists. References focusing on ocular hypertension were excluded., Results: Forty-eight articles addressing 1 of 4 criteria for neuroprotection were included. The literature confirms that brimonidine therapy meets the first 3 criteria for neuroprotection: receptors on its target tissues, adequate penetration into the vitreous and retina at pharmacologic levels, and induction of intracellular changes that enhance neuronal resistance to insults or interrupt apoptosis in animal models. Brimonidine did not meet the final neuroprotective criterion of success in humans., Conclusions: Experimental evidence has demonstrated that brimonidine is a potential neuroprotective agent. However, to date, clinical trials have failed to translate into similar efficacy in humans.

The objective of this study was to determine the pharmacokinetic parameters of clonidine during pregnancy compared with previously published data in nonpregnant subjects. Serial blood and urine samples were collected in 17 women during mid to late pregnancy over one steady-state dosing interval to determine clonidine noncompartmental pharmacokinetic parameters (n = 17) and creatinine clearance. In six of these pregnant subjects, maternal and umbilical cord (venous and arterial) plasma samples were collected at the time of delivery for measurement of clonidine concentrations. Clonidine apparent oral clearance was found to be 440 +/- 168 ml/min during pregnancy compared with 245 +/- 72 ml/min as previously reported in nonpregnant subjects (p < 0.0001) (Cunningham et al., 1994). There was a strong correlation (r = 0.82, p < 0.001) between clonidine renal clearance, adjusted for variation in glomerular filtration rate, and urine pH. Umbilical cord to maternal plasma clonidine concentration ratios were 1.0 +/- 0.1 (arterial) and 1.0 +/- 0.1 (venous). In conclusion, clonidine is cleared more rapidly in pregnant women than in nonpregnant subjects. At the time of delivery, the fetus is exposed to similar plasma clonidine concentrations as the mother.

The objective of this study was to evaluate the plasma pharmacokinetics of ketamine and its active metabolite norketamine administered intravenously at a dose of 0.1 mg/kg together with xylazine (0.05 mg/kg) to control the pain associated with castration in calves. A two-compartment model with an additional metabolite compartment linked to the central compartment was used to simultaneously describe the time-concentration profiles of both ketamine and its major metabolite norketamine. Parameter values estimated from the time-concentration profiles observed in this study were volume of the central compartment (V(c) = 132.82 +/- 68.23 mL/kg), distribution clearance (CL(D) = 15.49 +/- 2.56 mL/min/kg), volume of the peripheral compartment (V(T) = 257.05 +/- 41.65 mL/kg), ketamine clearance by the formation of the norketamine metabolite (CL(2M) = 8.56 +/- 7.37 mL/kg/min) and ketamine clearance by other routes (CL(o) = 16.41 +/- 3.42 mL/kg/min). Previously published data from rats suggest that the metabolite norketamine contributes to the analgesic effect of ketamine, with a potency that is one-third of the parent drug. An understanding of the time-concentration relationships and the disposition of the parent drug and its metabolite is therefore important for a better understanding of the analgesic potential of ketamine in cattle.

Background: The alpha2 agonist clonidine has become a popular drug for premedication in children. Effects and pharmacokinetics after oral, rectal, and intravenous administration are well known. The aim of this study was to investigate the absorption pharmacokinetics of clonidine nasal drops in children., Methods: Thirteen ASA I pediatric patients received after induction of anesthesia 4 mcg x kg(-1) of clonidine by the nasal route. Blood samples were taken during a 12-h period and plasma levels of clonidine were analyzed by liquid chromatography-mass spectrometry. Data were calculated by a computer-aided curve-fitting program., Results: Plasma pharmacokinetics following administration of clonidine nasal drops showed a considerable interindividual variability and absorption was delayed and limited. A total of 95% confidence intervals for maximum plasma concentration and time to achieve maximum plasma concentration were 0.4-0.6 ng x ml(-1) and 1.4-3.0 h, respectively., Conclusions: Clonidine nasal drops are erratically absorbed from the nasal mucosa and, thus, this mode of drug administration is not recommended for premedication purposes.

Background: Dexmedetomidine (DEX) is a highly selective alpha(2)-adrenoceptor agonist that has been used increasingly in children. However, the effect of caudal DEX has not been evaluated before in children. This prospective randomized double-blinded study was designed to evaluate the analgesic efficacy of caudal DEX with bupivacaine in providing pain relief over a 24-h period., Methods: Sixty children (ASA status I) aged 1-6 years undergoing unilateral inguinal hernia repair/orchidopexy were allocated randomly to two groups (n = 30 each). Group B received a caudal injection of bupivacaine 2.5 mg/ml, 1 ml/kg; Group BD received the same dose of bupivacaine mixed with DEX 1 microg/kg during sevoflurane anesthesia. Processed electroencephalogram (bispectral index score), heart rate, blood pressure, pulse oximetry and end-tidal sevoflurane were recorded every 5 min. The characteristics of emergence, objective pain score, sedation score and quality of sleep were recorded post-operatively. Duration of analgesia and requirement for additional analgesics were noted., Results: The end-tidal sevoflurane concentration and the incidence of agitation were significantly lower in the BD group (P < 0.05). The duration of analgesia was significantly longer (P < 0.001) and the total consumption of rescue analgesic was significantly lower in Group BD compared with Group B (P < 0.01). There was no statistically significant difference in hemodynamics between both groups. However, group BD had better quality of sleep and a prolonged duration of sedation (P < 0.05)., Conclusion: Caudal DEX seems to be a promising adjunct to provide excellent analgesia without side effects over a 24-h period. It has the advantage of keeping the patients calm for a prolonged time. Implications statement: Caudally administered DEX (1 microg/kg), combined with bupivacaine, was associated with an extended duration of post-operative pain relief.

Alpha2-adrenergic receptors (alpha2-adrenoceptors) mediate various physiological actions of endogenous catecholamines in the central and peripheral nervous systems being involved in alertness, heart rate regulation, vasomotor control and nociceptive processing. In the present study, the pharmacological profile of a novel alpha2-adrenoceptor agonist, fadolmidine, was studied in various in vitro and in vivo assays and compared to the well characterised alpha2-adrenoceptor agonist, dexmedetomidine. Fadolmidine displayed high affinity and full agonist efficacy at all three human alpha2-adrenoceptor subtypes (A, B and C) in transfected CHO cells with EC50 values (nM) of 0.4, 4.9 and 0.5, respectively. Fadolmidine inhibited also electrically evoked contractions in rat vas deferens demonstrating the activation of rodent presynaptic alpha2D-adrenoceptors with an EC50 value of 6.4 nM. Moreover, fadolmidine was a full agonist at human alpha1A-adrenoreceptor (EC50 value 22 nM) and alpha1B-adrenoreceptor (EC50 value 3.4 nM) in human LNCaP cells and transfected HEK cells, respectively. Agonism at the alpha1-adrenoceptor was also observed in rat vas deferens preparations although at lower potency (EC50 value 5.6 microM). Fadolmidine demonstrated potent alpha2-adrenoceptor agonist activity also in vivo by inhibiting electrically induced tachycardia in pithed rats and increasing mean arterial pressure in anaesthetised rats. However, after systemic administration, fadolmidine had considerably weaker CNS-mediated effects (mydriasis and sedation) compared to dexmedetomidine possibly due to limited penetration through the blood brain barrier by fadolmidine. In a conclusion, fadolmidine is a potent full agonist at all three alpha2-adrenoceptor subtypes with a pharmacological profile compatible with a therapeutic value e.g. after spinal administration.

Background: The alpha2-adrenergic agonist tizanidine has been reported to have a narrow therapeutic index. A multiparticulate capsule formulation of tizanidine has been developed in an attempt to improve patient tolerability., Objective: This study assessed bioequivalence between a single, intact, 6-mg capsule of tizanidine and the capsule contents sprinkled in applesauce in fasted healthy subjects., Methods: Healthy male and female subjects aged 18 to 45 years completed 2 treatment periods: one with a tizanidine 6-mg capsule administered intact and the other with capsule contents sprinkled in applesauce. The 2 treatment periods had a 6-day washout period between administrations. Plasma tizanidine concentrations were determined for blood samples collected over 24 hours after administration. All treatment-emergent adverse events were recorded and graded by intensity and relationship to the study drug (not, improbable, possible, probable, definite) by the attending physician based on his or her clinical impression., Results: A total of 19 men and 9 women (mean age, 26 years) completed the trial. Geometric mean natural logarithm-transformed AUC values (AUC(0-infinity) [AUC to infinity] and AUC(0-t) [AUC to the last measurable time point]) and C(max) ratios were significantly (P

Purpose: To determine and compare the human aqueous humor (AH) concentrations of 2 formulations of brimonidine ophthalmic solution [0.1% brimonidine Purite (BP) (average pH 7.4 to 8.0) and 0.15% BP (average pH 6.6 to 7.4)]., Patients and Methods: Single-center, randomized, controlled, double-masked, prospective study. Twenty-two patients were randomized to receive one 30-microL drop of 0.1% (n=11) or 0.15% BP (n=11) into the eye requiring routine cataract surgery. Solutions were administered approximately 40 to 55 minutes before surgery and AH samples (100 microL) were withdrawn from treated eyes at surgery initiation. Times from instillation to sampling were recorded. Brimonidine AH concentrations were assayed by high performance liquid chromatography-tandem mass spectrometry., Results: Mean brimonidine AH concentrations sampled 52+/-9 and 54+/-8 minutes (P=0.57) after instillation of 0.1% and 0.15% BP solutions were 59.4+/-42.7 and 95.5+/-87.5 ng/mL, respectively (P=0.23). When normalized for concentration differences between the 2 formulations, AH concentrations were similar (P=0.85). Both solutions were well tolerated with no adverse events observed., Conclusions: Brimonidine AH concentrations in human eyes after single doses of 0.1% or 0.15% BP ophthalmic solutions were proportional to the respective concentrations of the brimonidine formulation instilled. The pH difference between these 2 formulations seemed to exert no effect on brimonidine bioavailability or the tolerability of the solution.

Medetomidine is a chiral imidazole derivate whose dextroenantiomer is pharmacologically active. The major metabolic pathway of dexmedetomidine [(+)-4-(S)-[1-(2,3-dimethylphenyl)ethyl]-1H-imidazole] in humans is N-glucuronidation at the imidazolate nitrogens. We have purified the N3- and N1-glucuronides of dexmedetomidine, termed DG1 and DG2, respectively, according to their elution order in liquid chromatography and determined their structure by 1H nuclear magnetic resonance (NMR). Studying medetomidine glucuronidation by human liver microsomes (HLMs) and recombinant UDP glucuronosyltransferase (UGT) 1A4 indicated that another human UGT plays a major role in these activities. We now demonstrate that this enzyme is UGT2B10. HLMs catalyzed DG1 and DG2 formation, at a ratio of 3:1, with two-enzyme kinetics that contain both a high-affinity component, K(m1) values of 6.6 and 8.7 microM, and a low-affinity component, K(m2) values > 1 mM. The DG1/DG2 ratio in the case of UGT2B10 was lower, 1.4:1, whereas the substrate affinity for both reactions was high, K(m) values of 11 and 16 microM. UGT1A4 produced mainly DG1 (DG1/DG2 ratio of 6.6:1) at low substrate affinities, K(m) values above 0.6 mM, but superior expression-normalized V(max) values. Levomedetomidine [(-)-4-(R)-[1-(2,3-dimethylphenyl)ethyl]-1H-imidazole] glucuronidation by HLMs yielded mostly the N3-glucuronide (LG1, structure determined by NMR), with monophasic kinetics and a K(m) value of 14 microM. The activity of UGT1A4 toward levomedetomide was low and generated both LG1 and LG2, whereas UGT2B10 exhibited relatively high activity and sharp regioselectivity, yielding only LG1, with a K(m) value of 7.4 microM. The results highlight the contribution of UGT2B10 to medetomidine glucuronidation and its potential importance for other N-glucuronidation reactions within the human liver.

Background: Dexmedetomidine is an alpha-2 adrenoreceptor agonist with sedative, analgesic and anxiolytic properties. Since its release in the US market in late 1999, it has gained remarkable attention in the adult, pediatric and geriatric populations, predominantly because of its minimal respiratory depression. However, beyond its well-known properties, dexmedetomidine has recently been investigated for its potential in many other clinical scenarios, including neuroprotection, cardioprotection and renoprotection, with promising results., Objective: This review provides an outline of the current use of dexmedetomidine in adult and pediatric populations in several clinical settings, including operating room, intensive care unit, postsurgical patients and patients who need sedation and/or analgesia for invasive and noninvasive procedures. Our objectives were to examine the most up-to-date clinical evidence, describe the magnitude of effects, and shed some light on potential future applications., Methods: Published, peer-reviewed studies, including preclinical data, were included in this review article., Results/conclusions: Dexmedetomidine is a novel agent with a wide safety margin and excellent sedative and moderate analgesic properties. Though its broadest use is currently in surgical and nonsurgical intensive care unit patients, dexmedetomidine appears to have promising future applications in the areas of neuroprotection, cardioprotection and renoprotection.

Background: Sertindole is a second-generation antipsychotic recently reintroduced in the market for the treatment of schizophrenia after a reevaluation of its risks and benefits., Objective: This article provides an overview of the pharmacological properties of sertindole as well as of its efficacy, tolerability and safety profile., Methods: Several clinical trials and large-scale epidemiological studies have evaluated the efficacy and tolerability of sertindole in patients with schizophrenia., Results/conclusions: Findings from controlled clinical trials have demonstrated that sertindole is at least as effective as haloperidol and risperidone against the positive symptoms of schizophrenia, while it appears superior against negative symptoms. Preliminary evidence suggests that sertindole has beneficial effects on cognitive function. Sertindole is associated with a low rate of extrapyramidal side effects, lacks sedative properties, and may induce a moderate weight gain. No clinically relevant elevations in serum prolactin, glucose or lipid levels have been so far documented in sertindole-treated patients. On the other hand, administration of sertindole may result in a prolongation of the QTc interval, with subsequent risk of serious arrhythmias. However, postmarketing surveillance studies have recently indicated that sertindole is not associated with a higher rate of cardiovascular mortality than other antipsychotic agents.

Objectives: The objective of this investigation was to characterize the pharmacokinetic profile of lofexidine. Lofexidine is an orally bioavailable alpha 2-adrenergic receptor agonist analogue of clonidine that acts centrally to suppress opiate withdrawal symptoms., Methods: During the detoxification period of a phase 3 placebo-controlled, randomized, double-blind trial, six subjects were entered in this preliminary pharmacokinetic study., Results: Pharmacokinetic analysis of plasma samples collected during study day 7 indicated that C(max) was 3242 +/- 917 ng/L. The mean trough levels between the study days were not significantly different (p > .05), suggesting that the subjects were at steady-state., Conclusions: Although preliminary due to the limited number of subjects, these findings are the first to document lofexidine clinical pharmacokinetics in opiate addicts using a highly sensitive liquid chromatography tandem mass spectrometric analysis.

Objective: We studied the effects of gender and smoking on the pharmacokinetics and effects of the cytochrome P450 (CYP) 1A2 substrate tizanidine., Methods: Seventy-one healthy young volunteers (male and female nonsmokers, male smokers) ingested 4 mg tizanidine. Plasma concentrations and pharmacodynamics of tizanidine were measured, and a caffeine test was performed., Results: Among nonsmokers, the peak concentration (C(max)) and area under concentration-time curve from 0 to infinity [AUC(0-infinity)] of tizanidine did not differ significantly between females and males. However, the half-life (t(1/2)) was 9% shorter in female nonsmokers than in male nonsmokers (P < 0.05). In male smokers, the t(1/2) was 10% shorter and the weight-adjusted AUC(0-infinity) 33% smaller than in male nonsmokers (P < 0.05). The caffeine/paraxanthine ratio was 35-40% smaller (P = 0.001) in male smokers than in nonsmoking males or females, but did not differ between males and females. Tizanidine lowered blood pressure and caused drowsiness significantly (P < 0.05) more in females than in either male groups. The effects on blood pressure were smallest in male smokers (P < 0.05)., Conclusions: Gender by itself seems to have no clinically significant effect on the pharmacokinetics of tizanidine, whereas smoking reduces plasma concentrations and effects of tizanidine. Any possible effect of gender and smoking is largely outweighed by individual variability in CYP1A2 activity due to genetic and environmental factors and in body weight. Careful dosing of tizanidine is warranted in small females, whereas male smokers can require higher than average doses.