Does Fosamprenavir Interact with Efavirenz?
Fosamprenavir and Efavirenz have a unknown drug interaction according to U.S. FDA drug labeling data. This table includes potentially significant interactions, but is not all inclusive Table 5: Established and Other Potentially Significant Drug Interactions: Alteration in Dose or Regimen May Be Recommended Based on Drug Interaction Studies or Predicted Interaction Concomitant Drug Class: Drug Name Effect Clinical Comment HIV antiviral agents Protease inhibitor: Fosamprenavir calcium ↓ amprenavir Fosamprenavir (unboosted): Appropriate doses of the combinations with respect to safety and efficacy have not been established. Fosamprenavir/ritonavir: An additional 100 mg/day (300 mg total) of ritonavir is recommended when efavirenz tablets are administered with fosamprenavir/ritonavir once daily. No change in the ritonavir dose is required when efavirenz tablets are administered with fosamprenavir plus ritonavir twice daily. Patients taking both medications should consult their healthcare provider before starting, stopping, or changing the dosage of either drug. This information is based on official FDA drug labeling sourced from OpenFDA and the NIH National Library of Medicine.
- Severity
- Unknown
- Efavirenz Class
- Human Immunodeficiency Virus 1 Non-Nucleoside Analog Reverse Transcriptase Inhibitor
- Management
- Consult your pharmacist
- Data Source
- U.S. FDA via OpenFDA
What To Tell Your Doctor or Pharmacist
If you are taking Fosamprenavir and your doctor is considering prescribing Efavirenz (or vice versa), make sure to:
- Inform your doctor and pharmacist of all current medications, including over-the-counter drugs and supplements
- Ask whether the benefits of combining these medications outweigh the risks for your specific situation
- Ask what symptoms to watch for that would indicate the interaction is causing problems
- Never stop or change either medication without first consulting your healthcare provider