What the FDA labels say about taking them together
Fosamprenavir and rifampin
Fosamprenavir's FDA label of September 15, 2023 names rifampin in its contraindications section, and rifampin's label names fosamprenavir too. The fosamprenavir label: “Coadministration of fosamprenavir and drugs that induce CYP3A4, such as rifampin, may decrease amprenavir concentrations and reduce its therapeutic effect.”
Check it at the source: the fosamprenavir FDA label on DailyMed (effective September 15, 2023, Mylan Pharmaceuticals Inc.); the rifampin FDA label on DailyMed (effective February 11, 2026, Lupin Pharmaceuticals, Inc.).
What does the fosamprenavir label say about rifampin?
Fosamprenavir label, contraindicationsRifampin o Antipsychotic: Lurasidone (with ritonavir ), pimozide o Ergot derivatives: Dihydroergotamine, ergonovine, ergotamine, methylergonovine o GI motility agent:
Fosamprenavir label, drug interactionsCoadministration of fosamprenavir and drugs that induce CYP3A4, such as rifampin, may decrease amprenavir concentrations and reduce its therapeutic effect.
Source: FDA drug label (Fosamprenavir Calcium), Mylan Pharmaceuticals Inc., effective September 15, 2023 (SPL set 3a1424d8-844c-4e24-9ebd-b2c2b61b61a3), via openFDA; the full label on DailyMed
What does the rifampin label say about fosamprenavir?
Rifampin label, contraindicationsRifampin is contraindicated in patients who are also receiving atazanavir, darunavir, fosamprenavir, saquinavir, tipranavir, cabotegravir, fostemsavir and lenacapavir (see prescribing information for SUNLENCA) due to the potential of rifampin to substantially decrease plasma concentrations of these antiviral drugs, which may result in decreased antiviral efficacy and/or development of viral resistance. (See PRECAUTIONS, Drug Interactions ).
Source: FDA drug label (rifampin), Lupin Pharmaceuticals, Inc., effective February 11, 2026 (SPL set b56004f0-f23d-47f6-80c7-39884fccbccc), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Fosamprenavir | Rifampin | |
|---|---|---|
| Labeled for | HIV | n/a |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $0.679 per capsule 300 mg capsule |
| Shortage now | No current entry | In shortage |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once