Pharmacokinetics of isoniazid in Wistar rats exposed to ethanol

Abstract Tuberculosis treatment consists of a drug combination, where isoniazid is the core drug and alcoholism is a factor highly related to poor patient compliance with the therapy. CYP2E1 is an enzyme involved both in the metabolism of ethanol and in the formation of hepatotoxic compounds during the metabolism of isoniazid. The shared metabolism pathway accounts for the possibility of pharmacokinetic interaction in cases of concomitant alcohol use during tuberculosis treatment. The aim of this study was to evaluate the effect of repeated exposure of Wistar rats (males, 250 g, n=6) to ethanol on the pharmacokinetics of a single dose of isoniazid in combination with pyrazinamide and rifampicin (100 mg/kg, 350 mg/kg and 100 mg/kg, respectively). An animal group received the combination of drugs and ethanol and was compared to a control group, which received the combination of drugs without exposure to ethanol. The plasma concentrations of isoniazid were determined by a UHPLC/UV bioanalytical method that was previously validated. Biochemical markers of liver function were measured to assess potential damage. A lower elimination half-life of isoniazid was observed in the ethanol group than in the control group (t1/2 0.91 h versus 1.34 h). There was no evidence of hepatotoxicity through the biomarker enzymes evaluated. The results allow us to infer that although there are no biochemical changes related to liver damage, there is a slight influence of ethanol exposure on the pharmacokinetic profile of isoniazid. This change may have a relevant impact on the efficacy of isoniazid in the outcome of tuberculosis treatment.

Assessment of the Physicochemical Properties and Stability for Pharmacokinetic Prediction of Pyrazinoic Acid Derivatives.

BACKGROUND: Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis, which still has high prevalence worldwide. In addition, cases of drug resistance are frequently observed. In the search for new anti-TB drugs, compounds with antimycobacterial activity have been developed, such as derivatives of pyrazinoic acid, which is the main pyrazinamide metabolite. In a previous study, the compounds were evaluated and showed moderate antimycobacterial activity and no important cytotoxic profile; however, information about their pharmacokinetic profile is lacking. OBJECTIVE: The aim of this work was to perform physicochemical, permeability, and metabolic properties of four pyrazinoic acid esters. METHOD: The compounds were analyzed for their chemical stability, n-octanol:water partition coefficient (logP) and apparent permeability (Papp) in monolayer of Caco-2 cells. The stability of the compounds in rat and human microsomes and in rat plasma was also evaluated. RESULTS: The compounds I, II and IV were found to be hydrophilic, while compound III was the most lipophilic (logP 1.59) compound. All compounds showed stability at the three evaluated pHs (1.2, 7.4 and 8.8). The apparent permeability measured suggests good intestinal absorption of the compounds. Additionally, the compounds showed metabolic stability under action of human and rat microsomal enzymes and stability in rat plasma for at least 6 hours. CONCLUSION: The results bring favorable perspectives for the future development of the evaluated compounds and other pyrazinoic acid derivatives.

Simple and Rapid Method by Ultra High-Performance Liquid Chromatography (UHPLC) with Ultraviolet Detection for Determination of Efavirenz in Plasma: Application in a Preclinical Pharmacokinetic Study.

A simple and rapid ultra-high-performance liquid chromatography (UHPLC) method for determination of efavirenz (EFV) in plasma was developed and applied in a preclinical pharmacokinetic study. The method involves only addition of acetonitrile to precipitation of plasma proteins followed by solvent evaporation. The mobile phase consisted of methanol, acetonitrile and 0.1 M formic acid (20:50:30) at a flow rate of 0.3 mL/min with run time of 5 min. A CSH C18 column and a UHPLC-UV system operating at 245 nm were used. There was a linear response in the range of 0.078 to 10 µg/mL, and the equation was obtained by weighting (1/x2) with r2 = 0.9965. The pharmacokinetic disposition of EFV was investigated in rabbits (two groups, n = 7) following a single intravenous administration (IV group) at a dose of 2.7 mg/kg and a single oral administration (oral group) of EFV co-administered with lamivudine (3TC) and tenofovir (TNF) at a dose of 50, 25 and 25 mg, respectively. The study demonstrated the applicability of the method for determination of EFV in plasma without interference from other co-administered drugs, and the pharmacokinetic parameters were calculated. The method showed advantages over other methods in the literature, such as simplicity of sample processing and fast results.

New Pioglitazone Metabolites and Absence of Opened-Ring Metabolites in New N-Substituted Thiazolidinedione.

Thiazolidinediones (TZDs) are drugs used to treat type 2 diabetes mellitus; however, several safety concerns remain regarding the available drugs in this class. Therefore, the search for new TZD candidates is ongoing; metabolism studies play a crucial step in the development of new candidates. Pioglitazone, one of the most commonly used TZDs, and GQ-11, a new N-substituted TZD, were investigated in terms of their metabolic activity in rat and human liver microsomes to assess their metabolic stability and investigate their metabolites. Methods for preparation of samples were based on liquid-liquid extraction and protein precipitation. Quantitation was performed using liquid chromatography (LC)-tandem mass spectrometry, and the metabolite investigation was performed using ultraperformance LC coupled to a hybrid quadrupole-time of flight mass spectrometer. The predicted intrinsic clearance of GQ-11 was 70.3 and 46.1 ml/kg per minute for rats and humans, respectively. The predicted intrinsic clearance of pioglitazone was 24.1 and 15.9 ml/kg per minute for rats and humans, respectively. The pioglitazone metabolite investigation revealed two unpublished metabolites (M-D and M-A). M-A is a hydration product and may be related to the mechanism of ring opening and the toxicity of pioglitazone. The metabolites of GQ-11 are products of oxidation; no ring-opening metabolite was observed for GQ-11. In conclusion, under the same experimental conditions, a ring-opening metabolite was observed only for pioglitazone. The resistance of GQ-11 to the ring opening is probably related to N-substitution in the TZD ring.