Maintenance of high urinary pH is important during methotrexate treatment because:: (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
Answer is D. 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.