Prazosin

Prazosin In Dogs & Cats: Uses, Dosage and Side Effects

Overview

• Prazosin is a post-synaptic alpha-1 blocking agent causing arterial and venous vasodilation.
• This leads to a reduction in blood pressure and systemic vascular resistance.

Uses of Prazosin

• Promoting urine flow in patients with functional urethral obstruction.
• Management of systemic or pulmonary hypertension.
• Adjunctive therapy of congestive heart failure secondary to mitral or aortic regurgitation in cases refractory to standard therapy (not often used for this indication).
• Efficacy may decline over time.

Dose of Prazosin in Dogs and Cats

Dogs:

• To decrease urethral resistance in idiopathic vesicourethral reflex dyssynergia: 1 mg/15 kg body weight p.o. q12h.
• For adjunctive treatment for heart failure: 1 mg/dog p.o. q8–12h (dogs up to 15 kg); 2 mg/dog p.o. q8–12h (dogs >15 kg).
• Monitor efficacy by measuring blood pressure and clinical response.

Cats:

• 0.25–1 mg/cat p.o. q8–12h given initially for 5–7 days then wean off if possible.

Side Effects of Prazosin in Dogs and Cats

• Hypotension.
• Syncope.
• Drowsiness.
• Weakness.
• GI upsets.

Contraindications of Prazosin in Dogs and Cats

• Hypotension, renal failure.

Some Notes:

• Concomitant use of beta-blockers (e.g. propranolol) or diuretics (e.g. furosemide) may increase the risk of a first-dose hypotensive effect.
• Calcium-channel blockers may cause additive hypotension.
• Prazosin is highly protein-bound and so may be displaced by, or displace, other highly protein-bound drugs (e.g. sulphonamide) from plasma proteins.