This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chemotherapy, Subject name: Pharmacology
All of the following cause inhibition of CYP3A except 
Select and explain. 
A. Saquinavir, B. Ritonavir, C. Itraconazole, D. Erythromycin
A: Saquinavir
Answer: A: Saquinavir 
Explanation: All the drugs given in the option are microsomal enzyme inhibitors .Among protease inhibitor,ritonavir the strongest inhibitor of CYP3A4 enzymes whereas saquanivir is the weakest