HIV Postexposure Prophylaxis and the Need for Drug Interaction Screening


  • Roger Cheng ISMP Canada
  • Julie Greenall ISMP Canada
  • Christine Koczmara ISMP Canada
  • Sylvia Hyland ISMP Canada




Certain antiretroviral medications are known to be involved in numerous drug interactions through their inhibition of the cytochrome P450 system.1,2 One of the uses of antiretroviral medications is postexposure prophylaxis (PEP) against HIV, to reduce the risk of infection among people who may have been exposed to the virus, either through occupational exposure (e.g., needlestick injuries) or non-occupational exposure (e.g., sexual assault).3,4 To maximize effectiveness in this situation, antiretroviral therapy must be started as soon as possible (preferably within hours of exposure)3-5; therefore, if a person is deemed a suitable candidate for prophylaxis, an HIV PEP “starter kit” is often given to the patient in the emergency department or other ambulatory setting to ensure prompt initiation. When providing HIV PEP in this setting, a systematic approach for identifying possible drug interactions may be lacking. As illustrated by the following case, these interactions can have severe consequences if not promptly identified and resolved.


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Safe Medication Practices / Pratiques d'utilisation sécuritaire des médicaments