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Sildenafil

Prescription
Phosphodiesterase-5 (PDE5) inhibitor
Last reviewed 19 Apr 2026 · PetCare.AI Editorial Team
Species
Dog, Cat
Brands
3 available
Interactions
2 documented
Formulations
3

Mechanism of action

Selectively inhibits PDE5, increasing cGMP levels in pulmonary vascular smooth muscle, causing vasodilation and reducing pulmonary arterial pressure

At a glance

Class
Phosphodiesterase-5 (PDE5) inhibitor
Schedule
Prescription
Storage
Store below 30°C, protect from moisture

Dosing

🐕

Dog

Pulmonary hypertension
Dose
1–3 mg/kg
Route
PO
Frequency
BID to TID
Max dose
75 mg/dose; 225 mg/day
Duration: Long-term
🐈

Cat

Pulmonary hypertension
Dose
1–2 mg/kg
Route
PO
Frequency
BID to TID
Max dose
10 mg/dose; 30 mg/day
Duration: Long-term

Formulations

💊

Tablet — 3

Strength
25mg
Available in India
Strength
50mg
Available in India
Strength
100mg
Available in India

Storage

Store below 30°C, protect from moisture

Safety

Absolute contraindications — do not use

  • Concurrent nitrate therapy
    Severe hypotension risk
    Nitroglycerin

Use with caution

  • Systemic hypotension
    May worsen

Adverse effects

Common
Facial flushing
GI upset
Nasal congestion
Serious
Systemic hypotension
Priapism (rare)

Monitoring parameters

Blood pressureHeart rateExercise toleranceEchocardiography for pulmonary pressures

Interactions

Contraindicated — 1

Nitroglycerin (Transdermal)
contraindicated
Sildenafil + nitrate: synergistic cGMP-mediated vasodilation causing severe, potentially fatal hypotension.
Management: NEVER combine. Allow 24h washout of sildenafil before nitrate.

Moderate — 1

Amlodipine
moderate
Additive vasodilation and hypotension; both lower blood pressure via different mechanisms
Management: Monitor blood pressure. May need to reduce amlodipine dose.

Brands

International

Viagra
Pfizer

India

Penegra
Zydus
Manforce
Mankind

FAQs

Frequently asked questions

›What is Sildenafil?
Sildenafil is a phosphodiesterase-5 (pde5) inhibitor used in pets. Selectively inhibits PDE5, increasing cGMP levels in pulmonary vascular smooth muscle, causing vasodilation and reducing pulmonary arterial pressure
›What is Sildenafil used for in pets?
Sildenafil is used in veterinary medicine for: Pulmonary hypertension.
›What is the Sildenafil dose for dogs?
For dogs, Sildenafil is typically dosed as follows — Pulmonary hypertension: 1–3 mg/kg PO BID to TID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What is the Sildenafil dose for cats?
For cats, Sildenafil is typically dosed as follows — Pulmonary hypertension: 1–2 mg/kg PO BID to TID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What are the side effects of Sildenafil?
Common: Facial flushing, GI upset, Nasal congestion. Serious (call your vet immediately): Systemic hypotension, Priapism (rare).
›Does Sildenafil need a prescription?
Yes. Sildenafil is a prescription medication and should only be administered under veterinary supervision.
›When should Sildenafil not be used?
Do not use Sildenafil if: Concurrent nitrate therapy.

References

References

Textbooks & handbooks

  • Plumb, D.C. Plumb's Veterinary Drug Handbook. 10th ed., Wiley-Blackwell, 2023.
  • Vail, D.M., Thamm, D.H., & Liptak, J.M. (eds.). Withrow & MacEwen's Small Animal Clinical Oncology. 6th ed., Saunders/Elsevier, 2020.
  • Riviere, J.E., & Papich, M.G. (eds.). Veterinary Pharmacology and Therapeutics. 10th ed., Wiley-Blackwell, 2018.
  • National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press, Washington DC, 2006.
  • The Merck Veterinary Manual. Merck & Co., Online edition. https://www.merckvetmanual.com/

Clinical guidelines & consensus

  • Fletcher, D.J., Boller, M., Brainard, B.M., et al. "RECOVER Evidence and Knowledge Gap Analysis on Veterinary CPR." Journal of Veterinary Emergency and Critical Care, 2012;22(S1):S102–S131.
  • American Animal Hospital Association. 2018 AAHA Diabetes Management Guidelines for Dogs and Cats. AAHA Press.

Journals & peer-reviewed studies

  • Hogan, D.F., Fox, P.R., Jacob, K., et al. "Secondary prevention of cardiogenic arterial thromboembolism in the cat: The FAT CAT study." Journal of Veterinary Cardiology, 2015;17(Suppl 1):S306–S317.
  • Boswood, A., Häggström, J., Gordon, S.G., et al. "Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study — A Randomized Clinical Trial." Journal of Veterinary Internal Medicine, 2016;30(6):1765–1779.
  • ASPCA Animal Poison Control Center. Toxicology and Poison Management Guidelines. American Society for the Prevention of Cruelty to Animals. https://www.aspca.org/pet-care/animal-poison-control

Regulatory & approvals

  • Central Drugs Standard Control Organisation (CDSCO), Government of India. Veterinary Drug Approval Registry, 1969–2026. Directorate General of Health Services. https://cdsco.gov.in/

Databases

  • Washington State University, College of Veterinary Medicine. Veterinary Clinical Pharmacology Laboratory (VCPL) — MDR1 Multidrug Sensitivity Database. https://vcpl.vetmed.wsu.edu/
Educational reference only
This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →

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