Drug Interactions Corner

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HAART + warfarin = possible drug interaction


An article recently published in Pharmacotherapy describes two case reports of highly active antiretroviral therapy (HAART) for HIV disease significantly decreasing international normalized ratios (INRs) in patients concurrently receiving therapy with warfarin (Coumadin—Bristol-Myers Squibb). Both patients described in this article required higher than normal doses of warfarin to maintain therapeutic INRs.


Fulco PP et al. Possible antiretroviral therapy–warfarin drug interaction. Pharmacotherapy. 2008;28:945–9. 

Hughes CA et al. Interaction between lopinavir/ritonavir and warfarin. CMAJ. 2007;177:357–9. 

Bonora S et al. Drug interactions between warfarin and efavirenz or lopinavir/ritonavir in clinical treatment. Clin Infect Dis. 2008; 46:146–7. 

Cupp MJ et al. Cytochrome P450: new nomenclature and clinical implications. Am Fam Physician 1998;57:107–16.