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Database of Antiretroviral Drug Interactions

Interactions with Warfarin and Antiretrovirals

Antiretroviral (ARV)Dose of ARVDose of WarfarinEffect on ARV LevelsEffect on Warfarin LevelsPotential Clinical EffectsMechanism of InteractionManagement
Amprenavir60
(APV)(Agenerase)
- - - Not studied; may increase warfarin effectsIncreased warfarin effects (eg, increased INR, increased risk of bleeding)Inhibition of CYP450 3A4 by amprenavir

Monitor INR and adjust warfarin as indicated

Darunavir161
(DRV)(Prezista)
600 mg BID with ritonavir 100 mg BID10 mg x 1- S-warfarin AUC: decreased 21%;Decreased warfarin effects (eg, decreased INR, increased risk of clotting)Induction of CYP450 3A4 by darunavir

Monitor INR and adjust warfarin as indicated

Delavirdine88
(DLV)(Rescriptor)
- - - Not studiedIncreased warfarin effects (eg, increased INR, increased risk of bleeding)Inhibition of CYP450 3A4 and 2C9 by delavirdine

Monitor INR and adjust warfarin as indicated

Efavirenz90
(EFV)(Sustiva)
---Not studied; may increase or decrease warfarin levelsIncreased or decreased warfarin effects (altered INR, increased risk of bleeding or clotting)Possible inhibition or induction of CYP450 by efavirenz

Monitor INR and adjust warfarin as indicated

Elvitegravir/cobicistat623
(Genvoya, Stribild)
--- Not studied; may increase or decrease warfarin effectsPotential for over or under anticoagulation-

Monitor INR closely when pt is first initiating elvitegravir/cobicistat

Antiretroviral (ARV)Dose of ARVDose of WarfarinEffect on ARV LevelsEffect on Warfarin LevelsPotential Clinical EffectsMechanism of InteractionManagement
Elvitegravir/ritonavir-boosted protease inhibitor699
---Not studied; may increase warfarin levelsPotential increased risk of bleeding-

Monitor INR and adjust warfarin dose

Indinavir322
(IDV)(Crixivan)
800 mg Q8H x 12 days5 mg QD-Prothrombin complex activity increased from 25-35% to 53 and 43% at 10 and 25 days after indinavir discontinued in one patientIncreased warfarin effects (eg, increased INR, risk of bleeding)Inhibition of CYP450 by indinavir

Monitor INR and adjust warfarin as indicated

Lopinavir/ritonavir78
(LPV/r)(Kaletra)
---Not studied; may increase or decrease warfarin levelsIncreased or decreased warfarin effects (eg, altered INR, increased risk of bleeding or clotting)Possible inhibition of CYP450 by lopinavir/ritonavir

Monitor INR and adjust warfarin as indicated

Nevirapine95
(NVP)(Viramune)
----Possibly decreased warfarin effects (eg, altered INR, increased risk of clotting)-

Monitor INR and adjust warfarin as indicated

Ritonavir324
(RTV)(Norvir)
400 mg BID12.5 mg QD-INR: decreasedDecreased warfarin effects (eg, decreased INR, increased risk of clotting)Possible inhibition of CYP450 3A4, 2C9 and 1A2 by ritonavir

Monitor INR and adjust warfarin as indicated

Saquinavir323
(SQV)(Fortovase, Invirase)
600 mg TID x 8 weeks--Increased warfarin levels (INR increased from 2.1 to 4.24)Increased warfarin effects (eg, increased INR and risk of bleeding)Possible inhibition of CYP450 by saquinavir

Monitor INR and adjust warfarin as indicated

"-" indicates that there are no data available
 60:Agenerase [package insert]. Research Triangle Park, NC: Glaxo Wellcome Inc; 2004.
 78:Kaletra [package insert]. North Chicago, IL: Abbott Laboratories; Oct 2005.
 88:Rescriptor [package insert]. La Jolla, California: Agouron Pharmaceuticals, Inc; June 2001.
 90:Sustiva [package insert]. Princeton, NJ: Bristol-Myers Squibb Company; Dec 2011.
 95:Viramune [package insert]. Ridgefield, CT: Boehringer Ingelheim Pharmaceuticals, Inc.; Nov 2005.
 161:Prezista [package insert]. Raritan, NJ: Tibotec Therapeutics Inc.; April 2010.
 322:Gatti G, Alessabdrini A, Camera M, et al. Influence of indinavir and ritonavir on warfarin anticoagulation activity. [letter] AIDS. 1998;12:825-826.
 323:Darlington MR. Hypoprothrombinemia during concomitant therapy with warfarin and saquinavir. Ann Pharmacother 1997;31:647.
 324:Knoell KR, Young TM, Cousins ES. Potential interaction involving warfarin and ritonavir. Ann Pharmacother 1998;32:1299-302.
 623:Stribild [package insert]. Foster City, CA: Gilead Sciences, Inc.; August 2012.
 699:Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. Department of Health and Human Services. Available at http://aidsinfo.nih.gov/contentfiles/lvguidelines/AdultandAdolescentGL.pdf.