Gynaecology & Obstetrics All of the following drugs were found to reduce the efficacy of combined OCP when used together, EXCEPT: A Rifampin B Penicillin C Griseofulvin D Carbamazepine 💡 Explanation All of the following drugs were found to reduce the efficacy of combined OCP when used together, EXCEPT: ✓ Correct Answer: B. Penicillin