Interaction between warfarin and nafcillin: case report and review of the literature.

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Kim KY, Frey RJ, Epplen K, Foruhari F

Interaction between warfarin and nafcillin: case report and review of the literature.

Pharmacotherapy. 2007 Oct;27(10):1467-70.

PubMed ID

17896903 [ View in PubMed

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Abstract

A 39-year-old man with a history of deep vein thrombosis and septic arthritis of the left knee was treated with warfarin and cefazolin. Therapeutic prothrombin times and international normalized ratios (INRs) were maintained with warfarin 32 mg/week for approximately 1 month. When the patient's antibiotic regimen was changed from cefazolin to nafcillin 2 g every 4 hours, his INR declined significantly. His warfarin dosage had to be increased to a maximum of 88 mg/week to achieve a therapeutic INR. After completion of antibiotic therapy with nafcillin, the patient's warfarin requirements slowly declined over several weeks. A maintenance dosage of warfarin 42-48 mg/week was necessary after nafcillin discontinuation. Hepatic cytochrome P450 isoenzyme induction by nafcillin is likely the mechanism of a warfarin-nafcillin interaction. The usual onset of effect is within 1 week after starting nafcillin, and the offset of the effect is usually evident within 4 weeks after nafcillin discontinuation. In patients taking warfarin who are prescribed nafcillin, a 2-4-fold increase in the warfarin dose may be necessary, and clinicians should closely monitor INRs.

DrugBank Data that Cites this Article

Drug Enzymes

Drug	Enzyme	Kind	Organism	Pharmacological Action	Actions
Nafcillin	Cytochrome P450 3A4	Protein	Humans	Unknown	Inducer	Details