This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cytotoxic Anticancer Drugs, Subject name: Pharmacology
Maintenance of high urinary pH is impoant during methotrexate treatment because: 
Select and explain. 
A. Bladder irritation is reduced, B. It decreases renal tubular secretion of methotrexate, C. Leucovorin toxicity is increased in a dehydrated patient, D. Methotrexate is a weak acid
D: Methotrexate is a weak acid
Answer: D: Methotrexate is a weak acid 
Explanation: Methotrexate is a weak acid and is reabsorbed in acidic urinary pH. Higher plasma concentration may result in toxicity. Therefore, to decrease the reabsorption through renal tubules, high urinary pH must be maintained.