This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Contraceptives, Subject name: Gynaecology & Obstetrics
OCPs are C/I in pts receiving: 
Select and explain. 
A. Rifampicin, B. Ethambutol, C. Streptomycin, D. Pyrazinamide
A: Rifampicin
Answer: A: Rifampicin 
Explanation: Ans. is a, i.e. RifampicinRef: KDT 6th/ed, p317; Novak 14th/ed, p276Interactions of OCPs with other Drugs.Effect of other drugs on OCP's:Drugs reducing the effectiveness of OCPDrugs which increase the plasma level of steroids of OCP* RifampicinQ* CarbamazepineQ* Phenytoin* Ascorbic acid* Acetaminophen* Antifungals like- Griseofulvin- Ketoconazole- ItraconazoleInduce synthesis of cytochromeP450 enzymes in liver.* Ampicillin* TetracyclineKill gut bacteria and cause hydrolysis of steroid glucuronides in intestine.