Prazosin for Dogs - Dosage and Side Effects

Prazosin is a type of drug known as a alpha-adrenergic blocking agent or alpha-1 blocker. They work by blocking the effect of alpha-1-adrenergic receptors, G-protein-coupled receptors (GPCRs) which are found in various muscles and tissues. These receptors can constrict or relax muscles and tissues in the vascular system, urinary tract and other areas of the body.

It is a quinazoline derivative that is mainly used as an antihypertensive agent in both human and veterinary medicine. This is because it belongs to the group of peripherally acting antiadrenergic agents. Prazosin reduces total peripheral vascular resistance, which improves canine circulation and lowers dog blood pressure.

It should be noted that the antihypertensive action of prazosin is not accompanied by compensatory reflex tachycardia, unlike non-selective alpha-adrenergic receptor antagonists. Prazosin is not FDA regulated for veterinary use. This does not preclude it from use in dogs, but it is a prescription-only drug and its use needs to be authorized by a qualified veterinarian.

As an antihypertensive, prazosin is a drug that can be used in the treatment of various conditions in which its vasodilatory effect is beneficial for our canine companions. Among the main uses of prazosin in dogs, we can find:

• Treatment of hypertension (high blood pressure): is often caused by kidney or heart diseases or disorders or by certain medications. Many dogs have idiopathic causes of hypertension. Can be used specifically to treat pulmonary hypertension in dogs.
• Congestive heart failure: prazosin can also be used as part of the treatment of heart problems, such as congestive heart failure. This is because it helps reduce the pressure exerted on the heart and improves blood flow.
• Benign prostatic hyperplasia: this is a non-malignant cause of prostate enlargement which is most common in older dogs. Prazosin can be used as a therapy for these animals. It may even have some preventive use against malignant prostate cancer in dogs, but the research is inconclusive^[1].
• Urinary blockages: as it has action on the urinary tract, it can also be used to help relax the urethral sphincter to allow obstructions such as crystals in the dog's urine to pass more easily. Can also be used to treat bladder dysfunction more generally.
• Megaesophagus: as it can relax various bodily sphincters, it may have limited use in relaxing the lower esophageal sphincter, the malfunctioning of which is the cause of this condition.

We must stress that prazosin is not an over-the-counter drug. It should never be given to a dog without prescription from a trusted veterinary health professional.

The dosage of prazosin will depend on the medical condition of each animal and other factors to be determined by the vet. As a very rough guide, the most commonly used dose in the canine species is 0.05-0.1 mg/kg of body weight. This will be administered once or twice a day, depending on the problem to be treated and the veterinary recommendation. In certain cases, the veterinarian may adjust the dosage based on the animal's response.

As with all medications, the cost of prazosin will vary according to many factors. This include the country of purchase and manufacture, as well as the specific pricing guidelines by individual pharmacies.

Prazosin is mainly sold in capsule form of various strengths, ranging from 1-5 mg capsules. The stronger the preparation, the more expensive each individual capsule will be. Using Minipress as a guide, we can say the price for prazosin in the US averages around:

• 1 mg prazosin: around $0.41 per capsule.
• 5 mg prazosin: around $0.80 per capsule.

Some generic brands can be cheaper. Prices may also vary if you purchase prazosin online.

As with all medications, prazosin can cause undesirable side effects during treatment in our canine companions. These adverse effects are often related to its vasodilatory action. For example, it can excessively reduce blood pressure, especially if administered in high doses or at the beginning of treatment.

The most common side effects following the use of prazosin for dogs include:

• Hypotension
• Drowsiness
• Lethargy
• Weakness
• Nausea
• Vomiting
• Dizziness
• Collapse
• Changes in heart rate
• Allergic reaction

In an allergic reaction, we may observe swelling, hives or even respiratory difficulties. In extreme reactions, the dog may go into anaphylactic shock and will need to be taken to a veterinarian immediately. Other adverse effects of prazosin for dogs will usually cease after the drug stops being administered.

Whether sold under the trade name Minipress or another preparation, prazosin has various contraindications which will be considered by your veterinarian when prescribing the drug. Do not use prazosin in dogs:

• With pre-existing hypotension: i.e. those that already have low blood pressure for whatever reason.
• With severe kidney disease: the drug is excreted mainly through the kidneys. In these cases, it may remain in the body for longer, increasing its toxicity. Learn more about the symptoms and treatment of kidney failure in dogs with our related guide.
• With severe liver problems: the liver is the main organ responsible for metabolizing prazosin. Its use increases the risk of side effects.
• With hypersensitivity or allergy to prazosin: or to the excipients of medications containing it as an active ingredient.
• Undergoing treatment with medications that affect blood pressure: as well as those used to treat cardiovascular problems, since they could cause an excessive reduction in blood pressure.
• Are very young, old or debilitated: they are more sensitive to the possible side effects of prazosin.
• With severe heart disease: relaxation of blood vessels and alteration of blood flow may worsen their condition and cause adverse effects.

Unfortunately, heart failure can be difficult to observe, at least in its early stages. Read our guide to the signs and symptoms of heart failure in dogs to learn more.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

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