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Background: Gemfibrozil (Gem) is a drug that has been shown to activate PPAR‐α, a nuclear receptor that plays a key role in regulating lipid metabolism. Gem is used to lower the levels of triglycerides and reduce the risk of coronary heart disease in patients. Experimental studies in vitro and in vivo have shown that Gem can prevent or slow the progression of neurological disorders (NDs), including cerebral ischemia (CI), Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Neuroinflammation is known to play a significant role in these disorders. Method: The literature review for this study was conducted by searching Scopus, Science Direct, PubMed, and Google Scholar databases. Result: The results of this study show that Gem has neuroprotective effects through several cellular and molecular mechanisms such as: (1) Gem has the ability to upregulate pro‐survival factors (PGC‐1α and TFAM), promoting the survival and function of mitochondria in the brain, (2) Gem strongly inhibits the activation of NF‐κB, AP‐1, and C/EBPβ in cytokine‐stimulated astroglial cells, which are known to increase the expression of iNOS and the production of NO in response to proinflammatory cytokines, (3) Gem protects dopamine neurons in the MPTP mouse model of PD by increasing the expression of PPARα, which in turn stimulates the production of GDNF in astrocytes, (4) Gem reduces amyloid plaque pathology, reduces the activity of glial cells, and improves memory, (5) Gem increases myelin genes expression (MBP and CNPase) via PPAR‐β, and (6) Gem increases hippocampal BDNF to counteract depression. Conclusion: According to the study, Gem was investigated for its potential therapeutic effect in NDs. Further research is needed to fully understand the therapeutic potential of Gem in NDs. [ABSTRACT FROM AUTHOR]

Background and purpose: The study was aimed at validating a simple, rapid, and low-cost LC-MS/MS method for carvedilol and 4/-hydroxyphenyl carvedilol assay in human plasma. The validated method was applied to investigate the pharmacokinetics after a low dose of 6.25 mg. carvedilol. Experimental approach: In this study, the plasma was extracted by liquid-liquid extraction and evaporated the organic layer to dryness, then both analytes in the residue were reconstituted and detected by LC- MS/MS. The method was validated following the guideline on bioanalytical method validation. Thirty-one healthy volunteers participated in the pharmacokinetic study. After 10 h of fasting, each volunteer received one tablet of 6.25 mg carvedilol orally. Blood samples were collected at 16 prescheduled time points. The plasma samples were analyzed for pharmacokinetics. Findings/Results: The method was linear over a range of 0.050-50.049 ng/mL for carvedilol and 0.050-10.017 ng/mL for 4/-hydroxyphenyl carvedilol. Crucial validated results reached the requirements of selectivity, accuracy, precision, and stability. Pharmacokinetics of carvedilol and 4/-hydroxyphenyl carvedilol were evaluated which showed Cmax at 21.26 ± 9.23 and 2.42 ± 2.07 ng/mL; AUC0-t 66.95 ± 29.45 and 5.93 ± 3.51 ng.h/mL; AUC0-inf 68.54 ± 30.11 and 6.78 ± 3.49 ng.h/mL; and T1/2 6.30 ± 1.95 and 6.31 ± 6.45 h, respectively. Conclusion and implications: The validated method was able to detect and quantify both analytes in plasma samples and can be applied to the pharmacokinetic study of carvedilol and 4/-hydroxyphenyl carvedilol after receiving carvedilol at 6.25 mg orally. [ABSTRACT FROM AUTHOR]

Electrical field stimulation (EFS) induces contractions of both snake aorta and human umbilical cord vessels (HUCV) which were dependent on the presence of the endothelium. This study aimed to establish the nature of the mediator(s) responsible for EFS‐induced contractions in HUCV. Rings with or without endothelium from human umbilical artery (HUA) or vein (HUV) were mounted in organ bath chambers containing oxygenated, heated Krebs‐Henseleit's solution. Basal release of dopamine (DA), noradrenaline, and adrenaline was measured by LC‐MS‐MS. Cumulative concentration‐response curves were performed with dopamine in the absence and in the presence of L‐NAME or of dopamine antagonists. EFS studies were performed in the presence and absence of L‐NAME, the α‐adrenergic blockers prazosin and idazoxan, and the dopamine antagonists SCH‐23390 and haloperidol. Tyrosine hydroxylase (TH) and dopa‐decarboxylase (DDC) were studied by immunohistochemistry and fluorescence in situ hybridizations. Basal release of dopamine requires an intact endothelium in both HUA and HUV. TH and DDC are present only in the endothelium of both HUA and HUV as determined by immunohistochemistry. Dopamine induced contractions in HUA only in the presence of L‐NAME. Dopamine‐induced contractions in HUV were strongly potentiated by L‐NAME. The EFS‐induced contractions in both HUA and HUV were potentiated by L‐NAME and inhibited by the D2‐like receptor antagonist haloperidol. The α‐adrenergic antagonists prazosin and idazoxan and the D1‐like receptor antagonist SCH‐23390 had no effect on the EFS‐induced contractions of HUA and HUV. Endothelium‐derived dopamine is a major modulator of HUCV reactivity in vitro . [ABSTRACT FROM AUTHOR]

Central nervous system (CNS) HIV infection causes brain tissue inflammation and tissue deficit that contributes to neuroAIDS. This complication is escalated by the blood–brain barrier (BBB), which prevents easy access to antiretroviral drugs entering the CNS. In this study the aims were to investigate the BBB membrane penetration and brain localization patterns of Nevirapine (NVP) using Imaging Mass Spectrometry (MSI). Sprague–Dawley rats received an intraperitoneal dose of NVP (50 mg kg−1). Plasma and brain samples were harvested, and mass spectrometric methods were then applied to determine the pharmacokinetic properties and localization patterns of NVP in the brain. The pharmacokinetic parameters demonstrated a rapid bio-distribution of NVP in plasma and brain. The plasma Cmax was 6320 ng mL−1 and the brain Cmax was 1923 ng mL−1, both at a Tmax of 0.25 h. MSI of coronal brain sections showed that NVP penetrated and localized in the brain regions implicated with the development of HIV associated neurodegeneration. NVP has great potential to combat neuroAIDS. [ABSTRACT FROM AUTHOR]

Introduction: This article describes the method development approaches for bioassay of substances containing unstable functional groups and forming unstable metabolites using the example of mycophenolic acid, methyldopa and mebeverine metabolites. Materials and Methods: The concentration of mycophenolic acid, which contains one phenolic hydroxyl and forms glucuronides during metabolism, was measured in plasma using HPLC-MS/MS, HPLC-MS and GC-MS. The determination of methyldopa, containing two phenolic hydroxyls, in stabilised plasma was performed by HPLC-MS/MS in the range of 0.02-3.00 µg/ml. Desmethyl mebeverine acid, which contains one phenolic hydroxyl and is metabolised by forming phenolic glucuronide, was assayed simultaneously with mebeverine acid in the range of 10-2000 ng/ml. Results and Discussion: The selection of storage conditions of the samples containing unstable substances should begin with selecting an anticoagulant based on the study of its short-term stability and freeze/thaw stability. If an unacceptable result is obtained, a combination of the anticoagulant and a stabiliser solution, as well as a concentration of this solution and its volume ratio to the biological fluid should be titrated. After which, this method should be validated by using the selected anticoagulant or the combination of the anticoagulant and stabiliser solution. Conclusion: The application of this approach to developing a bioanalytical method for determination of unstable compounds makes it possible to avoid obtaining false assay results. [ABSTRACT FROM AUTHOR]

A nanosensor was introduced for a sensitive determination of methyldopa using multiwall carbon nanotubes (MWCNTs) decorated with ferrite nickel nanoparticles (NiFeO) on a glassy carbon electrode. The electrochemical activity of the modified electrode for the determination of methyldopa was investigated using differential pulse voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy. The results showed that the modified electrode exhibits synergistic activity to the oxidation of methyldopa. The influence of several parameters that affect the response of the modified electrode was studied. A wide linear dynamic range of 0.5 to 900 μmol L methyldopa with a detection limit of 0.08 μmol L was achieved using differential pulse voltammetry. The interference of foreign substances on the selectivity of the electrochemical sensor was evaluated. Finally, the proposed method was successfully applied for the determination of methyldopa in real samples such as human urine, tablet, and plasma with satisfactory results. [ABSTRACT FROM AUTHOR]

Background: Dexmedetomidine is a highly selective a2-adrenoceptor agonist that is widely used for sedation and analgesia during the perioperative period. Intravenous administration of dexmedetomidine induces transient hypertension due to vasoconstriction via the activation of the a2-adrenoceptor on vascular smooth muscle. The goal of this in vitro study is to investigate the calcium-dependent mechanism underlying dexmedetomidine-induced contraction of isolated endothelium-denuded rat aorta. Methods: Isolated endothelium-denuded rat thoracic aortic rings were suspended for isometric tension recording. Cumulative dexmedetomidine concentration-response curves were generated in the presence or absence of the following inhibitors: a2-adrenoceptor inhibitor rauwolscine; voltage-operated calcium channel blocker verapamil (5 × 10-7, 10-6 and 5 × 10-5 M); purported inositol 1,4,5-trisphosphate receptor blocker 2-aminoethoxydiphenylborate (5 × 10-6, 10-5 and 5 × 10-5 M); phospholipase C inhibitor U-73122 (10-6 and 3 × 10-6 M); and store-operated calcium channel inhibitor gadolinium chloride hexahydrate (Gd3+; 5 × 10-6 M). Dexmedetomidine concentration-response curves were also generated in low calcium concentrations (1 mM) and calcium-free Krebs solution. Results: Rauwolscine, verapamil, and 2-aminoethoxydiphenylborate attenuated dexmedetomidine-induced contraction in a concentration-dependent manner. Low calcium concentrations attenuated dexmedetomidine-induced contraction, and calcium-free Krebs solution nearly abolished dexmedetomidine-induced contraction. However, U-73122 and Gd3+ had no effect on dexmedetomidine-induced contraction. Conclusions: Taken together, these results suggest that dexmedetomidine-induced contraction is primarily dependent on extracellular calcium concentrations that contribute to calcium influx via voltage-operated calcium channels of isolated rat aortic smooth muscle. Dexmedetomidine-induced contraction is mediated by a2-adrenoceptor stimulation. Dexmedetomidine-induced contraction appears to be partially mediated by calcium release from the sarcoplasmic reticulum. [ABSTRACT FROM AUTHOR]

Knowledge of the stability of drugs in biological samples is important for the interpretation of toxicological findings. This paper reviews data on the stability of drugs in blood, plasma, or serum. Since such data have already been reviewed for classic drugs of abuse, the focus here is on newer drugs of abuse and on therapeutic drugs. Key information about the conditions of the stability experiments will be provided and the following drugs or drug classes are covered: amphetamines, amphetamine-derived, piperazine-derived, and phenethylamine-derived designer drugs, antidepressants, neuroleptics, anti-HIV drugs, antiepileptics, cardiovascular drugs, and others. In addition, aspects of stability experiments and their evaluations are discussed. The data presented show that the majority of drugs are stable in blood, plasma, or serum samples under the conditions usually encountered in a clinical or forensic toxicology laboratory. Instability usually only occurs for drugs carrying ester moieties, sulfur atoms, or other easily oxidized or reduced structures. Nevertheless, clinical or forensic specimens should always be stored at least in the refrigerator and preferably at −20 °C or lower to avoid any degradation. Finally, results obtained from biosamples that have been stored at room temperature for a longer time should be interpreted with great care and partial degradation should always be considered. [ABSTRACT FROM AUTHOR]