This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharmacokinetics, Subject name: Pharmacology
Oral contraceptive failure occurs by intake of: 
Select and explain. 
A. Rifampicin, B. Penicillin, C. Chloroquine, D. Metronidazole
A: Rifampicin
Answer: A: Rifampicin 
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.