Does Rifampin Interact with Fosamprenavir?
Rifampin and Fosamprenavir have a contraindicated drug interaction according to U.S. FDA drug labeling data. Concomitant use is contraindicated. Rifampin decreases fosamprenavir AUC by 82%. The mechanism involves cyp3a4 induction; auc decreased by 82%. 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
- Contraindicated
- Rifampin Class
- Rifamycin Antibacterial
- Management
- Do not take together
- Data Source
- U.S. FDA via OpenFDA
How This Interaction Works
The interaction between Rifampin and Fosamprenavir occurs because cyp3a4 induction; auc decreased by 82%. Clinically, this means concomitant use is contraindicated. rifampin decreases fosamprenavir auc by 82%. Because of the severity of this interaction, these medications are contraindicated — meaning they should not be taken together under any circumstances. If you are currently taking both, contact your healthcare provider immediately to discuss alternatives.
What To Tell Your Doctor or Pharmacist
If you are taking Rifampin and your doctor is considering prescribing Fosamprenavir (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
- Ask about alternative medications that do not interact with your current regimen
- Ask how frequently you should be monitored while these are co-prescribed
- Never stop or change either medication without first consulting your healthcare provider