This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Contraception, Subject name: Gynaecology & Obstetrics
Oral contraceptive Pill (OCP) failure is seen with all except: 
Select and explain. 
A. Rifampicin, B. Phenobarbitone, C. Valproate, D. Phenytoin
C: Valproate
Answer: C: Valproate 
Explanation: Drugs leading to OCP failure are: Rifampicin Tetracyclines Phenytoin Phenobarbitone Antifungals Cephalosporin Ritonavir for HIV (interferes with absorptionn of OCP) Ref: online resources (ncb.nlm.nih.gov)