tagamet and Altretamine Interactions

Interactions between tagamet(cimetidine) and Altretamine (altretamine)

cimetidine and altretamine (Moderate Drug-Drug)

GENERALLY AVOID: According to a rat model, the coadministration with cimetidine may increase the half-life and toxicity of altretamine. The likely mechanism is cimetidine inhibition of altretamine metabolism via CYP450 isoenzymes. In the study, 20 to 120 mg/kg of cimetidine (up to 114% of recommended human dose based on BSA) increased in a dose-related manner the half-life of altretamine by 29% to 80%. Cimetidine 120 mg/kg increased the toxicity of a single 350 mg/kg dose of altretamine from LD30 to LD75. In contrast, ranitidine had no significant effect on half-life or toxicity of altretamine.

MANAGEMENT: Based on animal data as well as human case reports of increased toxicity when other antineoplastic agents have been administered with cimetidine, the concomitant use of altretamine and cimetidine should generally be avoided if possible. Ranitidine may be a safer alternative if H2-antagonist therapy is necessary. Famotidine and nizatidine may also be considered, since they have not been shown to interfere with CYP450 metabolism.