title: Studies on the toxic interaction between monensin and tiamulin in rats: effects on P450 activities.
abstract: Studies were carried out to investigate the effects of monensin and tiamulin, and the simultaneous administration of both compounds on microsomal enzymes in rats. In Phase I of the experiments the effects of monensin and tiamulin were studied separately (monensin 10, 30, and 50 mg/kg or tiamulin 40, 120, and 200 mg/kg body weight, respectively), while in Phase II the two compounds were administered simultaneously (monesin 10 mg/kg and tiamulin 40 mg/kg b.w., respectively). When monensin was administered by itself, it exerted no significant effect on microsomal liver enzymes. In a few cases, slight inhibition of certain enzyme activities was seen. Tiamulin provoked a dose-dependent hepatic enzyme induction. The combined administration of monensin and tiamulin at low doses (10 and 40 mg/kg, respectively) resulted in marked elevation of P450-related enzyme activities. The enzyme induction was more pronounced in females than in males. The results suggest that the simultaneous administration of tiamulin may influence the biotransformation of monensin, possibly increasing the amount of reactive metabolite(s) of the ionophore antibiotic.
authors.affiliation: Department of Toxicology, EGIS Pharmaceuticals Ltd, H-1475 Budapest 10, P.O. Box 100, Hungary.
authors.forename: G
authors.initials: G
authors.lastname: Szücs
authors.forename: P
authors.initials: P
authors.lastname: Laczay
authors.forename: J
authors.initials: J
authors.lastname: Bajnógel
authors.forename: Z
authors.initials: Z
authors.lastname: Móra
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000633:toxicity*; D001835:Body Weight / Q000187:drug effects; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004224:Diterpenes / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D007476:Ionophores / Q000633:toxicity*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D008985:Monensin / Q000633:toxicity*; D009929:Organ Size / Q000187:drug effects; D051381:Rats
chemical_list: D000900:Anti-Bacterial Agents; D004224:Diterpenes; D007476:Ionophores; D003577:Cytochrome P-450 Enzyme System; D008985:Monensin; C014224:tiamulin