JEAN M. NAPPI, PHARM.D.
To the editor: In their excellent review on antiepileptic drugs in the February issue, Drs. Penry and Newmark (1) note that dicumarol may prolong the half-life of phenytoin. The potential interaction of warfarin and phenytoin was not mentioned and deserves attention, since both of these drugs are commonly prescribed.
The package insert (2) does not list phenytoin as a drug that can influence the prothrombin time of a patient maintained on warfarin therapy. Deykin (3), however, includes phenytoin in a group of drugs that may potentiate the action of warfarin, presumably by inhibiting its metabolism. Koch-Weser (4) has reported this
NAPPI JM. Warfarin and Phenytoin Interaction. Ann Intern Med. ;90:852. doi: 10.7326/0003-4819-90-5-852_1
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Published: Ann Intern Med. 1979;90(5):852.
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