title: The effect of rifampicin and pyrazinamide on isoniazid pharmacokinetics in rats.
abstract: Tuberculosis chemotherapy involves combination of the drugs isoniazid (INH), rifampicin (RMP) and pyrazinamide (PYR) for a 6-month period. The present work investigated the influence of RMP and PYR on the pharmacokinetic parameters of INH when groups of rats were pre-treated for 21 days with INH alone or in combination with RMP and/or PYR, in the following amounts per kg body weight: INH 100 mg; INH 100 mg+RMP 100 mg; INH 100 mg+PYR 350 mg; INH 100 mg+PYR 350 mg+RMP 100 mg. It was found that the co-administration of PYR caused an increase in the INH distribution volume (V(d)/F), half-life of elimination (t(1/2beta)) and clearance (Cl(T)/F), and a decrease in the area under curve 0 to 24 h (AUC). Co-administration of RMP caused an increase in the Cl(T)/F and a decrease in the AUC. The combination INH+PYR+RMP caused an increase in the Cl(T)/F and a decrease in the AUC. These significant pharmacokinetic interactions between the tuberculostatic drugs might be related to differences in the therapeutic and toxic effects.
authors.affiliation: Departamento de Princípios Ativos Naturais e Toxicologia, Faculdade de Ciências Farmacêuticas, Universidade Estadual Paulista, Araraquara, SP, Brasil.
authors.forename: Helen M
authors.initials: HM
authors.lastname: Baldan
authors.forename: Helene J
authors.initials: HJ
authors.lastname: De Rosa
authors.forename: Iguatemy L
authors.initials: IL
authors.lastname: Brunetti
authors.forename: Valdecir F
authors.initials: VF
authors.lastname: Ximenes
authors.forename: Rosângela G P
authors.initials: RG
authors.lastname: Machado
mesh_terms: D000818:Animals; D000904:Antibiotics, Antitubercular / Q000494:pharmacology*; D000995:Antitubercular Agents / Q000493:pharmacokinetics* / Q000494:pharmacology*; D019540:Area Under Curve; D002851:Chromatography, High Pressure Liquid; D004347:Drug Interactions; D006207:Half-Life; D007538:Isoniazid / Q000493:pharmacokinetics*; D008297:Male; D011718:Pyrazinamide / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012293:Rifampin / Q000494:pharmacology*