Drug-Drug Interactions

Relationships between HIV or HIV therapy and the potential for cardiovascular (CV) issues have been shown to exist in a number of areas. These include significant drug-related CV toxicities, such as hyperlipidemia or diabetes, and an increased probability of CV comorbidity compared with the general population.1 Additionally, there is potential for a number of drug-drug interactions (DDIs) between HIV and CV medications.1

Low-level evidence suggests potential DDIs between warfarin and a number of antiretroviral (ARV) medications in the protease inhibitor (PI) and non-nucleoside reverse-transcriptase inhibitor (NNRTI) classes, in particular:2

  • atazanavir
  • darunavir
  • fosamprenavir
  • indinavir
  • lopinavir
  • nelfinavir
  • ritonavir
  • saquinavir
  • tipranavir
  • delavirdine
  • efavirenz
  • etravirine
  • nevirapine

In each case, the limited evidence suggests that co-administration with warfarin may affect (increase or decrease) the plasma concentration of warfarin. Monitoring of the International Normalized Ratio (INR) is therefore essential.

There have also been case reports of interactions between efavirenz and atazanavir/ritonavir with acenocoumarol and so caution is advised before prescribing these therapies together. The authors also noted that they did not identify any complications with the concurrent use of raltegravir with acenocoumarol.3

Access the HIV drug interactions website 

Additionally, patients on warfarin (a vitamin K antagonist) therapy should avoid vitamin supplements containing vitamin K, and limit the intake of foods that are high in vitamin K, such as:4

  • broccoli
  • cabbage
  • red and green lettuce
  • onion
  • spinach
  • oils, particularly rapeseed, soybean and olive oil
  • leaf teas


  1. Dau B, Holodniy M. The Relationship Between HIV Infection and Cardiovascular Disease. Curr Cardiol Rev. 2008;4(3):203–218.
  2. HIV drug interactions. The Liverpool HIV Pharmacology Group (LHPG) Accessed 13 April 2011.
  3. Welzen ME, van den Berk GE, Hamers RL, Burger DM. Interaction between antiretroviral drugs and acenocoumarol. Antivir Ther. 2011;16(2):249–252. 
  4. Nutescu EA, Shapiro NL, Ibrahim S, West P. Warfarin and its interactions with foods, herbs and other dietary supplements. Expert Opin Drug Saf. 2006;5(3):433–451.