Is Sildenafil (PDE5 inhibitors) safe for dogs and cats?
Moderate risk for petsSildenafil (Viagra, Revatio) is used therapeutically in dogs — veterinary medicine uses sildenafil for pulmonary arterial hypertension (PAH) and portopulmonary hypertension, conditions where PDE5 inhibition reduces pulmonary vascular resistance. Therapeutic veterinary doses are well-characterized (1–2 mg/kg every 8 hours for PAH in dogs). However, accidental ingestion of human sildenafil tablets (25 mg, 50 mg, 100 mg) is a frequent cause of veterinary presentations due to the drug's household prevalence and palatability. The primary toxicity in dogs from acute overdose is vasodilation-mediated hypotension: clinical signs include lethargy, weakness, facial flushing/erythema, hypotension, reflex tachycardia, and in severe cases, collapse. Concurrent ingestion with other vasodilators, nitrates, or antihypertensive agents markedly increases hypotension risk. Other PDE5 inhibitors (tadalafil, vardenafil, avanafil) present the same mechanism of toxicity. A specific concern in brachycephalic breeds: these dogs have elevated baseline pulmonary pressures and may respond more dramatically to PDE5 inhibition. Treatment for overdose is primarily supportive: fluid resuscitation for hypotension, monitoring, and time (sildenafil has a 3–5 hour half-life in dogs).
What is sildenafil (pde5 inhibitors)?
The IUPAC name is 5-[2-ethoxy-5-(4-methylpiperazin-1-yl)sulfonylphenyl]-1-methyl-3-propyl-6H-pyrazolo[4,5-d]pyrimidin-7-one.
Also known as: 5-[2-ethoxy-5-(4-methylpiperazin-1-yl)sulfonylphenyl]-1-methyl-3-propyl-6H-pyrazolo[4,5-d]pyrimidin-7-one, sildenafil, Aphrodil, Vizarsin.
- IUPAC name
- 5-[2-ethoxy-5-(4-methylpiperazin-1-yl)sulfonylphenyl]-1-methyl-3-propyl-6H-pyrazolo[4,5-d]pyrimidin-7-one
- CAS number
- 139755-83-2
- Molecular formula
- C22H30N6O4S
- Molecular weight
- 474.6 g/mol
- SMILES
- CCCC1=NN(C2=C1N=C(NC2=O)C3=C(C=CC(=C3)S(=O)(=O)N4CCN(CC4)C)OCC)C
- PubChem CID
- 135398744
Risk for dogs
Moderate riskSildenafil (Viagra, Revatio) is used therapeutically in dogs — veterinary medicine uses sildenafil for pulmonary arterial hypertension (PAH) and portopulmonary hypertension, conditions where PDE5 inhibition reduces pulmonary vascular resistance. Therapeutic veterinary doses are well-characterized (1–2 mg/kg every 8 hours for PAH in dogs). However, accidental ingestion of human sildenafil tablets (25 mg, 50 mg, 100 mg) is a frequent cause of veterinary presentations due to the drug's household prevalence and palatability. The primary toxicity in dogs from acute overdose is vasodilation-mediated hypotension: clinical signs include lethargy, weakness, facial flushing/erythema, hypotension, reflex tachycardia, and in severe cases, collapse. Concurrent ingestion with other vasodilators, nitrates, or antihypertensive agents markedly increases hypotension risk. Other PDE5 inhibitors (tadalafil, vardenafil, avanafil) present the same mechanism of toxicity. A specific concern in brachycephalic breeds: these dogs have elevated baseline pulmonary pressures and may respond more dramatically to PDE5 inhibition. Treatment for overdose is primarily supportive: fluid resuscitation for hypotension, monitoring, and time (sildenafil has a 3–5 hour half-life in dogs).
Regulatory consensus
3 regulatory and scientific bodies have classified Sildenafil (PDE5 inhibitors). The classifications differ — that's the data.
| Agency | Year | Classification | Notes |
|---|---|---|---|
| FDA | — | Approved for erectile dysfunction (ED) in men | At standard doses 25–100 mg as needed |
| FDA | — | Approved for pulmonary arterial hypertension (PAH) | Revatio formulation, all sexes, at lower doses 20 mg TID |
| US | — | Prescription-only | Current status; OTC proposals have been reviewed but not approved |
Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.
Where pets encounter sildenafil (pde5 inhibitors)
- Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
- Occupational Environments — Factories, Warehouses, Transportation vehicles
Safer alternatives
Lower-risk approaches that achieve a similar outcome to Sildenafil (PDE5 inhibitors):
-
Alternative drug class; Non-pharmacological therapy; Lowest effective dose
Trade-offs: Direct chemical substitution requires verification that the replacement does not introduce new hazards (regrettable substitution). Conduct full hazard assessment of proposed alternative before adoption.Relative cost: 1.2-2×
Frequently asked questions
Is sildenafil (pde5 inhibitors) safe for pets?
Sildenafil (Viagra, Revatio) is used therapeutically in dogs — veterinary medicine uses sildenafil for pulmonary arterial hypertension (PAH) and portopulmonary hypertension, conditions where PDE5 inhibition reduces pulmonary vascular resistance. Therapeutic veterinary doses are well-characterized (1–2 mg/kg every 8 hours for PAH in dogs). However, accidental ingestion of human sildenafil tablets (25 mg, 50 mg, 100 mg) is a frequent cause of veterinary presentations due to the drug's household prevalence and palatability. The primary toxicity in dogs from acute overdose is vasodilation-mediated hypotension: clinical signs include lethargy, weakness, facial flushing/erythema, hypotension, reflex tachycardia, and in severe cases, collapse. Concurrent ingestion with other vasodilators, nitrates, or antihypertensive agents markedly increases hypotension risk. Other PDE5 inhibitors (tadalafil, vardenafil, avanafil) present the same mechanism of toxicity. A specific concern in brachycephalic breeds: these dogs have elevated baseline pulmonary pressures and may respond more dramatically to PDE5 inhibition. Treatment for overdose is primarily supportive: fluid resuscitation for hypotension, monitoring, and time (sildenafil has a 3–5 hour half-life in dogs).
What products contain sildenafil (pde5 inhibitors)?
Sildenafil (PDE5 inhibitors) appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments).
Why do regulators disagree about sildenafil (pde5 inhibitors)?
Sildenafil (PDE5 inhibitors) has been classified by 3 agencies including FDA, FDA, US, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.
See Sildenafil (PDE5 inhibitors) in the pets app
Look up products containing sildenafil (pde5 inhibitors), compare to alternatives, and explore the full data record.
Open in pets View raw API dataSources (3)
- US FDA: Sildenafil (Viagra/Revatio) Prescribing Information — Erectile Dysfunction, Pulmonary Arterial Hypertension, Nitrate Contraindication, and Cardiovascular Risk (2020) — regulatory
- ASPCA Animal Poison Control Center: Sildenafil and PDE5 Inhibitor Toxicosis in Dogs — Hypotension, Clinical Signs, and Supportive Management (2023) — veterinary
- Plumb's Veterinary Drug Handbook (10th ed.) — Sildenafil: Veterinary Use for Pulmonary Hypertension and Accidental Ingestion Management (2023) — veterinary
Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →