What the FDA labels say about taking them together
Cobicistat and sildenafil
Cobicistat's FDA label of February 10, 2026 names sildenafil in its contraindications section; the sildenafil labels PlainMeds reads (4) do not name cobicistat. The cobicistat label: “… Use of PDE-5 inhibitors for pulmonary arterial hypertension (PAH): Use of sildenafil is contraindicated when used for the treatment of PAH due to potential for sildenafil-associated adverse reactions. …”
Check it at the source: the cobicistat FDA label on DailyMed (effective February 10, 2026, Gilead Sciences, Inc.); the sildenafil FDA label on DailyMed (effective November 17, 2023, Viatris Specialty LLC).
What does the cobicistat label say about sildenafil?
Cobicistat label, contraindicationsSt. John's wort ( Hypericum perforatum ) Hormonal Contraceptives: drospirenone/ ethinyl estradiol Lipid-modifying Agents: lomitapide, lovastatin, simvastatin Non-nucleoside Reverse Transcriptase Inhibitor: nevirapine Phosphodiesterase-5 (PDE-5) Inhibitor: sildenafil when administered as Revatio ® for the treatment of pulmonary arterial hypertension Protease Inhibitor: indinavir Sedative/hypnotics triazolam, orally administered midazolam Coadministration with certain drugs for which altered plasma concentrations are associated with serious and/or life-threatening events or loss of therapeutic effect.
Cobicistat label, drug interactionsConcomitant Drug Class/Drug Name: Phosphodiesterase-5 (PDE-5) Inhibitors: avanafil sildenafil tadalafil vardenafil; Potential Effect ↑ = Increase, ↓ = Decrease, ↔ = No change: ↑ PDE-5 inhibitors; Clinical Comment: Coadministration with avanafil is not recommended because a safe and effective avanafil dosage regimen has not been established. Coadministration with TYBOST coadministered with atazanavir or darunavir may result in an increase in PDE-5 inhibitor associated adverse events, including hypotension, syncope, visual disturbances, and priapism. …
Source: FDA drug label (Tybost), Gilead Sciences, Inc., effective February 10, 2026 (SPL set 3784c35c-e87f-410c-900b-8fd6313c6010), via openFDA; the full label on DailyMed
What does the sildenafil label say about cobicistat?
Sildenafil's label (effective November 17, 2023) and its 3 other brand-application labels do not name cobicistat 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
| Cobicistat | 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 | A presentation being discontinued | 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