What the FDA labels say about taking them together
Fosamprenavir and sildenafil
Fosamprenavir's FDA label of September 15, 2023 names sildenafil in its contraindications section; the sildenafil labels PlainMeds reads (4) do not name fosamprenavir. The fosamprenavir label: “… Use of PDE5 inhibitors for pulmonary arterial hypertension (PAH): Use of sildenafil (REVATIO) is contraindicated when used for the treatment of PAH. …”
Check it at the source: the fosamprenavir FDA label on DailyMed (effective September 15, 2023, Mylan Pharmaceuticals Inc.); the sildenafil FDA label on DailyMed (effective November 17, 2023, Viatris Specialty LLC).
What does the fosamprenavir label say about sildenafil?
Fosamprenavir label, contraindicationsSildenafil (REVATIO ® ) (for treatment of pulmonary arterial hypertension) o Sedative/hypnotics: Midazolam, triazolam
Fosamprenavir label, drug interactionsConcomitant Drug Class/Drug Name: PDE5 inhibitors: Sildenafil, tadalafil, vardenafil; Effect on Concentration of Amprenavir or Concomitant Drug: ↑ Sildenafil ↑ Tadalafil ↑ Vardenafil; Clinical Comment: May result in an increase in PDE5 inhibitor-associated adverse events, including hypotension, syncope, visual disturbances, and priapism. Use of PDE5 inhibitors for pulmonary arterial hypertension (PAH): Use of sildenafil (REVATIO) is contraindicated when used for the treatment of PAH. A safe and effective dose has not been established when used with fosamprenavir. …
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 sildenafil label say about fosamprenavir?
Sildenafil's label (effective November 17, 2023) and its 3 other brand-application labels do not name fosamprenavir in these sections. A label lists what its studies and reports found; it is not a complete list.
Source: FDA drug label (Viagra), Viatris Specialty LLC, effective November 17, 2023 (SPL set d905dc8d-917f-4ea3-a4ee-a1ecf6967d4e), 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 | Sildenafil | |
|---|---|---|
| Labeled for | HIV | Erectile dysfunction, Pulmonary arterial hypertension |
| Boxed warning | No | No |
| Pharmacy cost (NADAC) | n/a | $0.132 per tablet 100 mg tablet |
| Shortage now | No current entry | No current entry |
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