Pharmacology Pharmacokinetics 72d2945a Oral contraceptive failure occurs by intake of: A Rifampicin B Penicillin C Chloroquine D Metronidazole High-Yield Explanation Ans. is 'a' Rifampicin Rifampicin is an enzyme inducer. It induces the metabolism of oral contraceptives and reduce cone, of OCP's in the body.