Interaction of cimetidine with oral melphalan. A pharmacokinetic study.

The effects of pretreatment with cimetidine (200 mg three times daily, 400 mg at night) on the pharmacokinetics of oral melphalan (10 mg) have been investigated in patients with multiple myeloma. Cimetidine pretreatment reduced the bioavailability of oral melphalan by approximately 30% (P less than 0.05). The elimination rate of melphalan from plasma was significantly increased by cimetidine (P less than 0.05), the half-life being reduced from 1.94 +/- 0.55 h to 1.57 +/- 0.53 h. Cimetidine appeared to reduce the interindividual variability in melphalan absorption, but at the cost of reduced bioavailability.