Veterinary drug · Drug monograph

Prazosin: veterinary dose and monograph

Prazosin is a veterinary drug. Alpha-1 adrenergic blocker: relaxes urethral smooth muscle (functional urethral obstruction, reflex dyssynergia, urethral spasm after obstruction) and causes arterial and venous dilation (hypertension, adjunct in heart failure). Indications include functional urethral obstruction / urethral spasm (dogs, cats); systemic hypertension; adjunct vasodilator in heart failure (dogs). This monograph lists 4 reference doses for dogs and cats, each with route, frequency and source.

At a glance

Drug class: Veterinary drug
Also known as: Minipress, Prazopress
Species with doses: Dogs and Cats
Routes: PO, IV
Last reviewed: 1 October 2026

Indications

Functional urethral obstruction / urethral spasm (dogs, cats)
Systemic hypertension
Adjunct vasodilator in heart failure (dogs)

Prazosin dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

Prazosin doses for dogs
Indication	Dose	Route	Frequency	Duration
Functional urethral obstruction / reflex dyssynergia	1 mg per 15 kg PO q8–24h	PO	q8–24h	—
Hypertension / heart failure (adjunct)	Hypertension 1–4 mg per dog PO q12–24h; heart failure 1 mg q8h (<15 kg) or 2 mg q8h (>15 kg)	PO	q8–24h	—

Functional urethral obstruction / reflex dyssynergia: Plumb’s p.996: 1 mg per 15 kg q8h (Lane), q8–24h (Lulich), q12–24h (Bartges; Vernau), two to three times daily (Dickinson). Papich 5e: 0.5–2 mg per dog q8–24h. Often combined with a skeletal-muscle relaxant (dantrolene, diazepam).
Hypertension / heart failure (adjunct): Plumb’s p.996: heart failure 1 mg q8h for dogs <15 kg, 2 mg q8h for dogs >15 kg (Atkins; Kittleson); hypertension 1–4 mg q12–24h (Brown & Henik). Monitor blood pressure.

Cats

Prazosin doses for cats
Indication	Dose	Route	Frequency	Duration
Urethral spasm / functional obstruction	0.25–1 mg per cat PO q8–24h (start 0.5 mg q8h after obstruction)	PO	q8–24h	—
Urethral spasm (IV)	0.03 mg/kg	IV	single dose	—

Urethral spasm / functional obstruction: Papich 5e: 0.25–1 mg per cat (≈0.07 mg/kg) q8–12h; after urethral obstruction 0.5 mg q8h initially, then 0.25–0.5 mg once daily. Plumb’s p.996: 0.5 mg q8h (Lane); 0.25–0.5 mg q12–24h (Coates; Lulich); 0.25–1 mg q8–12h for 5–7 days then wean (Gunn-Moore & Casey).
Urethral spasm (IV): Plumb’s p.996 (Lane; Osborne 2000): 0.03 mg/kg IV. Monitor blood pressure.

Contraindications

Hypotension or hypovolaemia; significant renal failure (hypotension). Give the first dose when the animal can be observed — first-dose hypotension/syncope possible.

Adverse effects

Hypotension, weakness, syncope (especially first dose)
Lethargy
GI upset

Monitoring

Blood pressure
Urine stream / residual volume

Formulations and products

1 mg capsule/tablet
2 mg capsule/tablet
5 mg capsule/tablet

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Frequently asked questions

What is the dose of Prazosin for dogs?

Reference doses for Prazosin in dogs: 1 mg per 15 kg PO q8–24h PO q8–24h (Functional urethral obstruction / reflex dyssynergia); Hypertension 1–4 mg per dog PO q12–24h; heart failure 1 mg q8h (<15 kg) or 2 mg q8h (>15 kg) PO q8–24h (Hypertension / heart failure (adjunct)). Confirm against the label and the patient before use.

What is the dose of Prazosin for cats?

Reference doses for Prazosin in cats: 0.25–1 mg per cat PO q8–24h (start 0.5 mg q8h after obstruction) PO q8–24h (Urethral spasm / functional obstruction); 0.03 mg/kg IV single dose (Urethral spasm (IV)). Confirm against the label and the patient before use.

When should Prazosin not be used?