Sildenafil is a widely used, veterinarian-prescribed PDE-5 inhibitor that relaxes blood vessels in the lungs, effectively lowering pulmonary blood pressure. It is the treatment of choice for canine and feline pulmonary arterial hypertension (PAH), cor pulmonale, and certain congenital heart defects with right-to-left shunting.
Key Benefits
- Rapidly improves clinical signs (lethargy, syncope, exercise intolerance, cough)
- Increases quality of life and exercise capacity
- Well-tolerated in most dogs and cats when dosed appropriately
Common Uses
- Primary or secondary pulmonary hypertension
- Heart worm disease-related PAH
- Left-sided congestive heart failure with secondary pulmonary hypertension
- Megaoesophagus (off-label, to reduce lower esophageal sphincter pressure in dogs)
Typical Dosage (veterinary use only – always follow your vet’s instructions)
- Dogs: 0.5–3 mg/kg by mouth every 2–3 times daily (most common range 1–2 mg/kg q8–12h)
- Cats: 0.5–2 mg/kg by mouth every 8–12 hours
Tablets can be split or compounded into flavoured liquids/suspensions for precise dosing and easier administration.
Possible Side Effects
- Mild: facial flushing, redness of skin/ears, mild hypotension
- Gastrointestinal upset (vomiting, decreased appetite)
- Rare: priapism, sudden blindness (SARDS-like syndrome reported in humans, extremely rare in pets)
Important
Sildenafil should NOT be used with nitrates or in animals with severe liver/kidney disease without veterinary supervision. Always start at the lowest effective dose and monitor blood pressure when possible.