This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Concomitant treatment with which of the following can cause OCP failure 
Select and explain. 
A. Enalapril., B. Metformin, C. Ibuprofen, D. Rifampicin
D: Rifampicin
Answer: D: Rifampicin 
Explanation: Rifampicin