Sildenafil
Also known as: Viagra, Revatio, Aphrodil
> **Important**: Sildenafil is often prescribed "off-label" in veterinary medicine to treat high blood pressure in the lungs (pulmonary hypertension). * **What to expect**: You may notice your pet has more energy, less coughing, and fewer fainting spells (syncope). * **Cost**: Because this is a human medication (often known as Viagra® or Revatio®), it can be expensive. Discuss compounding or generic options with your veterinarian if cost is a concern. * **Safety Warning**: **NEVER** give your pet any other heart medications, especially **nitrates** (like nitroglycerin), while they are on sildenafil, as this combination can cause a fatal drop in blood pressure. * **Side Effects**: Watch for redness or flushing on the belly (inguinal area) or stomach upset. Contact your vet if your pet seems dizzy, lethargic, or collapses.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- Moderate to severe PH secondary to either left heart disease or primary lung disease
- Pulmonary arterial hypertension
- Pulmonary hypertension
- Pulmonary hypertension documented by Doppler, chronic pulmonary disease, right-sided heart failure (HW disease; congenital)
- Moderate to severe PH secondary to either left heart disease or primary lung disease
- Pulmonary hypertension
- Pulmonary arterial hypertension
How it is given
Possible side effects
- Cutaneous flushing of the inguinal region
- Gastrointestinal effects (possible)
- Headache, visual disturbances, dyspepsia, nasal congestion, myalgia, priapism, dizziness, and back pain (reported in humans)
- Vomiting
- Dizziness / weakness
- Raised intraocular pressure
- Systemic hypotension (especially if combined with other vasodilators)
Cautions & contraindications
- Concurrent use with organic nitrates
- Known hypersensitivity to sildenafil
- Pulmonary veno-occlusive disease (PVOD)
- Systemic hypotension
- Significant hepatic impairment
- Significant renal impairment
- Bleeding disorders
- Concurrent use of nitrates
- > **WARNING**: Sildenafil should not be used concurrently with nitrates due to the risk of life-threatening hypotension. * Pulmonary vasodilators may significantly worsen the cardiovascular status of patients with pulmonary veno-occlusive disease (PVOD). * Use with **extreme caution** in patients with resting hypotension, fluid depletion, severe left ventricular outflow obstruction, or autonomic dysfunction.
Drug interactions
- Alpha-adrenergic blockers (e.g., phentolamine, phenothiazines, phenoxybenzamine): May increase hypotensive effects
- Amlodipine: Potential to increase hypotensive effects
- Antihypertensive, hypotensive drugs: Potentially could increase hypotensive effects
- Azole antifungals (ketoconazole, itraconazole): May reduce sildenafil metabolism and increase AUC
- Cimetidine: May reduce sildenafil metabolism and increase AUC
- Erythromycin, Clarithromycin: May reduce sildenafil metabolism and increase AUC
- Heparin: May increase bleeding risks
- Nitrates (e.g., NTG, Isosorbide): Significant potentiation of vasodilatory effects; life-threatening hypotension possible
- Nitroprusside sodium: Significant potentiation of vasodilatory effects; life-threatening hypotension possible
- Phenobarbital: May decrease sildenafil concentrations
- Rifampin: May decrease sildenafil concentrations
Frequently asked questions
What is Sildenafil used for in pets?
> **Important**: Sildenafil is often prescribed "off-label" in veterinary medicine to treat high blood pressure in the lungs (pulmonary hypertension). * **What to expect**: You may notice your pet has more energy, less coughing, and fewer fainting spells (syncope). * **Cost**: Because this is a human medication (often known as Viagra® or Revatio®), it can be expensive. Discuss compounding or generic options with your veterinarian if cost is a concern. * **Safety Warning**: **NEVER** give your pet any other heart medications, especially **nitrates** (like nitroglycerin), while they are on sildenafil, as this combination can cause a fatal drop in blood pressure. * **Side Effects**: Watch for redness or flushing on the belly (inguinal area) or stomach upset. Contact your vet if your pet seems dizzy, lethargic, or collapses.
Is Sildenafil safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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