Cimetidine enhances cisplatin toxicity in mice.

The combination of the histamine H2 antagonist cimetidine (CMT) and the anticancer agent cisplatin (CDDP) was studied in normal and tumorbearing mice. CMT doses of 100 mg/kg produced no alteration in the survival of DBA/2J mice bearing P388 leukemia treated with CDDP doses of 3 mg/kg or 6 mg/kg. In these groups, the median survival was 13 days and 16 days, respectively, compared to 10 days in untreated controls. However, when adult CD-1 mice were given higher but nonlethal CDDP doses of 10, 15, or 18 mg/kg, the addition of CMT significantly increased CDDP lethality (P less than 0.05 by Wilcoxon analysis). For the 3 groups, CMT-enhanced lethality occurred in 10% of mice given 10 mg/kg CDDP, 80% of mice given 15 mg/kg, and 100% of mice given 18 mg/kg CDDP. Thus, CMT can acutely alter CDDP toxicity without affecting antitumor efficacy in mice.