# 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.

Source: https://vetmasterji.com/drugs/prazosin · Last reviewed: 2026-10-01

## 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

> **Caution:** 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.

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## 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?

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

### What are the side effects of Prazosin in animals?

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

## Sources

- Plumb's Veterinary Drug Handbook
- Papich 5e — Prazosin
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.