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
Dose reduction should be done for which of the following anticancer drug, if Allopurinol is used 
Select and explain. 
A. Methotrexate, B. Mitoxantrone, C. 6-Mercaptopurine, D. Mitomycin-C
C: 6-Mercaptopurine
Answer: C: 6-Mercaptopurine 
Explanation: Allopurinol inhibits the metabolism of 6-mercaptopurine and result in toxicity. Therefore if Allopurinol is used, dose of 6-mercaptopurine should be decreased by 75%.