GARY J. ALGOZZINE, B.S.; RONALD B. STEWART, M.S.; PHILLIP K. SPRINGER, M.D.
To the editor: Cimetidine has been shown to decrease the metabolism of a number of drugs, namely, diazepam (1), chlordiazepoxide (2), oral anticoagulants (3), theophylline (4), and most recently propranolol (5). Inhibition of hepatic microsomal enzyme systems, specifically P-450 hydroxylation reactions are likely responsible along with decreased liver blood flow. Glucuronidation reactions are spared because lorazepam and oxazepam are unaffected by concomitant Cimetidine therapy (6).
Recently, we observed another important interaction in which Cimetidine likely inhibited phenytoin levels.
A 31-year-old white woman was treated with Dilantin, 100 mg three times daily, for a seizure disorder secondary to trauma. After approximately
ALGOZZINE GJ, STEWART RB, SPRINGER PK. Decreased Clearance of Phenytoin with Cimetidine. Ann Intern Med. ;95:244–245. doi: 10.7326/0003-4819-95-2-244_2
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Published: Ann Intern Med. 1981;95(2):244-245.
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