Study of the pharmacokinetic interaction between ethinylestradiol and amoxicillin in rabbits

Abstract

Several antibiotics have been implicated in oral contraception failure when they are administered at the same time as the oral contraceptive (OC) pill. In the present paper, a study about amoxicillin-ethinylestradiol (EE22 pharmacokinetic potential interaction was studied. Two rabbit groups were utilized, the first group received amoxicillin (10 mg/kg) and EE 22 (30, 50 and 100 µg/kg, respectively), both by intravenous (i.v.) route. The second group received amoxicillin (oral route, 10 mg/kg/day) and EE 22 (i.v. route, 100 µ/kg) on day 1,4 and 8 of antibiotic treatment, respectively. After compartmental (two-compartment open model) and non-compartmental analysis of plasma concentrations, the statistical study (ANOVA p< 0.05) revealed that the presence of amoxicillin did not modify the EE 22 distribution and elimination pharmacokinetic parameters (by comparison with those obtained in a previous stud y where E22 was administered alone). There also were no significant differences with the time of amoxicillin oral treatment.