Maraviroc and Fosamprenavir: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Fosamprenavir
Maraviroc
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Increased maraviroc concentrations
Interaction Deep Dive
When maraviroc was coadministered with fosamprenavir/ritonavir, the maraviroc AUC increased 2.3- to 2.5-fold. The concomitant use of maraviroc (a CYP3A substrate) with fosamprenavir (a CYP3A inhibitor) is contraindicated in adult and pediatric patients with CrCl less than 30 mL/min and in those with ESRD on regular hemodialysis. In adults with CrCl 30 mL/min or greater taking both maraviroc and fosamprenavir (with or without a strong CYP3A inducer), reduce the maraviroc dose to 150 mg orally twice daily. In pediatric patients with CrCl 30 mL/min or greater, reduce the dose as follows: 50 mg twice daily for those 10 to less than 20 kg, 75 mg (if taking the tablet) or 80 mg (if taking oral solution) twice daily for those 20 to less than 30 kg), 100 mg twice daily for those 30 to less than 40 kg, and 150 mg twice daily for those 40 kg or greater. When fosamprenavir is coadministered with maraviroc, add ritonavir1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated maraviroc metabolism
Literature reports
1 report — tap to read
a) Concomitant administration of fosamprenavir/ritonavir and maraviroc resulted in increased maraviroc AUC and plasma concentrations. When fosamprenavir 700 mg/ritonavir 100 mg twice daily was administered concurrently with maraviroc 300 mg twice daily in 14 patients, the ratio of maraviroc pharmacokinetic parameters with fosamprenavir/ritonavir to without fosamprenavir/ritonavir was: minimum concentration (Cmin) 4.74 (90% CI, 4.03 to 5.57), AUC 2.49 (90% CI, 2.19 to 2.82), and Cmax 1.52 (90% CI, 1.27 to 1.82). When concomitant administration of fosamprenavir 1400 mg/ritonavir 100 mg once daily was administered with maraviroc 300 mg once daily in 14 patients, the ratio of maraviroc pharmacokinetic parameters with fosamprenavir/ritonavir to without fosamprenavir/ritonavir was: Cmin 1.8 (90% CI, 1.53 to 2.13), AUC 2.26 (90% CI, 1.99 to 2.58), and Cmax 1.45 (90% CI, 1.2 to 1.74)1.
Common questions
Can I take Maraviroc and Fosamprenavir together?
Increased maraviroc concentrations Always confirm with your pharmacist or prescriber before making any change.
How serious is the Maraviroc and Fosamprenavir interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "established". Well documented — supported by controlled studies or strong clinical data.
Questions for your pharmacist
- Does my dose of Maraviroc or Fosamprenavir need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Product Information: SELZENTRY(R) oral tablets, oral solution, maraviroc oral tablets, oral solution. Viiv Healthcare (per FDA), Research Triangle Park, NC, 2018. DailyMed
Keep reading about Fosamprenavir
Keep reading about Maraviroc
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Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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