What the FDA labels say about taking them together
Sapropterin and sildenafil
Sapropterin's FDA label of August 26, 2024 names sildenafil in its drug interactions section; the sildenafil labels PlainMeds reads (4) do not name sapropterin. The sapropterin label: “Drugs Affecting Nitric Oxide‑Mediated Vasorelaxation Clinical Impact Both sapropterin dihydrochloride and PDE-5 inhibitors may induce vasorelaxation. A reduction in blood pressure could occur; …”
Check it at the source: the sapropterin FDA label on DailyMed (effective August 26, 2024, BioMarin Pharmaceutical Inc.); the sildenafil FDA label on DailyMed (effective November 17, 2023, Viatris Specialty LLC).
What does the sapropterin label say about sildenafil?
Sapropterin label, drug interactionsDrugs Affecting Nitric Oxide‑Mediated Vasorelaxation (e.g., PDE-5 inhibitors such as sildenafil, vardenafil, or tadalafil) Clinical Impact Both sapropterin dihydrochloride and PDE-5 inhibitors may induce vasorelaxation. A reduction in blood pressure could occur; however, the combined use of these medications has not been evaluated in humans. Intervention Monitor blood pressure. Inhibitors of Folate Synthesis (e.g., methotrexate, valproic acid, phenobarbital, trimethoprim):
Source: FDA drug label (Kuvan), BioMarin Pharmaceutical Inc., effective August 26, 2024 (SPL set af38711e-8873-4790-a92d-4d583e23fb89), via openFDA; the full label on DailyMed
What does the sildenafil label say about sapropterin?
Sildenafil's label (effective November 17, 2023) and its 3 other brand-application labels do not name sapropterin 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
| Sapropterin | Sildenafil | |
|---|---|---|
| Labeled for | n/a | 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