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A 45-year-old man whose prothrombin time had been maintained at 30 seconds by daily administration of warfarin was treated with a histamine antagonist. After 3 weeks of treatment, he developed impotence and hematomas. Which of the following drugs is most likely to have caused these problems?

(A) Cimetidine
(B) Diphenhydramine
© Hydroxyzine
(D) Ranitidine
(E) Terfenadine

Is it that Cimetidine inhibits P450 system --> increased warfarin --> inability to clot;.
Cimetidine also causes gynecomastia & impotence