- Medication type: Smooth muscle relaxant, Sympatholytic
- Form: Liquid, Capsule, Tablet
- Prescription required? Yes
- FDA approved? No
- Life stage: Adult, Senior
- Brand names: Minipress, Minizide, Hypovase, Pratisol
- Common names: prazosin hydrochloride
- Available dosages: Capsules and tablets = 1mg, 2mg, 5mg; Available as a compounded liquid at as-needed dosage.
- Expiration range: Read package label carefully. Store and discard according to labeled instructions.
Prazosin is an oral medication that is often used along with other medications to treat and manage urethral obstructions in cats. A urethral obstruction happens when mucus, crystals, stones, or other debris forms a plug in a cat’s urethra—which is the exit path urine takes out of the bladder. When a plug forms, a cat is unable to urinate.
A cat who can’t pee has a life-threatening problem. A cat with a urethral obstruction requires emergency care by a veterinarian who can dislodge the plug and empty the bladder.
What is Prazosin?
Prazosin is prescribed to cats most often during the healing phase following a urinary blockage. When a urinary obstruction occurs, the muscles of the bladder and the urethra may spasm, (contract and release) and create an uncomfortable condition. These spasms and the swelling that can result make it more difficult for a cat to heal.
Prazosin can be helpful in reducing spasms and relaxing the bladder, making it easier for the cat to urinate and to heal.
This medication may also be useful for cats with spinal cord injuries or certain cancers.
Prazosin is not approved by the FDA for use in animals, but veterinarians often prescribe it and recommend it to treat feline patients. It is widely available from human pharmacies with a prescription from your veterinarian. Some veterinary clinics may also have the medication in stock.
Because prazosin for cats is usually prescribed as a generic medication, the look of the tablets or capsules may differ depending on where it was produced. If you have any concerns about the accuracy of the medication, contact your veterinarian or the pharmacy where the medication was purchased.
How Does Prazosin Work?
Prazosin decreases the function of the pathway that allows the bladder to fill and store urine. It works by decreasing the ability of specific muscles to tighten. It also can decrease blood pressure by allowing relaxation of the muscles that surround some arteries.
It is useful for cats recovering from a urinary blockage because it also allows the muscles of the urethra to relax, making it easier for urine to pass.
The muscles involved in the storage of urine in the bladder and tightening of the urethra to prevent urine from passing are what we refer to as smooth muscle. Smooth muscle is not under voluntary control as opposed to muscles of the legs and arms. This means that prazosin is unlikely to cause your cat to drip urine. Instead, it just makes it easier to go when your cat gets to the litter box.
Other types of muscle relaxants that are prescribed for muscle injury from trauma or overuse are not effective at relaxing the smooth muscles of the bladder and urethra.
What Does Prazosin Treat in Cats?
Prazosin treats the spasming of the bladder muscles and muscles of the urethra that is caused by urinary obstruction. It makes it easier for the cat to empty his bladder and reduces any pain or discomfort associated with the muscle spasms. Prazosin is most often used as part of the treatment for this problem along with other treatments including intravenous fluid therapy, pain management, and a special prescription diet.
Prazosin may also be used to relax the bladder and make it easier for pet parents to manually empty. This may be required following trauma, spinal cord injury, or surgery when a cat is unable to control his bladder.
Prazosin does not cure the cause of cat urinary blockage. They may be caused by feline urinary crystals, stress, or a genetic predisposition. Urinary obstructions are very likely to recur without lifelong changes that include a prescription urinary diet and stress management.
Due to limited documented evidence, not all veterinarians recommend prazosin as part of the treatment plan for cats with a urinary obstruction.
Prazosin Side Effects in Cats
Most cats tolerate prazosin without any side effects. Rarely, a cat may have low blood pressure due to prazosin. Some cats become hyperactive when taking prazosin.
Like any medication, mild side effects of prazosin in cats vary because every animal tolerates the medicine differently. If you notice any undesired changes in your cat while taking prazosin contact your veterinarian immediately.
Reactions With Other Drugs or Medications
Prazosin should be used with caution with other medications that can decrease blood pressure such as benazepril.
Prazosin Dosages for Cats
Prazosin is dosed based on weight and is best given with food. It may be given 2 or 3 times per day, depending on your cat’s particular situation and the dosage amount prescribed by your veterinarian.
What if My Cat Misses a Dose of Prazosin?
If your cat misses a dose of prazosin, skip that dose and give the next dose at the appropriate time.
Prazosin may only need to be given for a few days to weeks following a urinary obstruction. Do not stop using prazosin without consulting with your cat’s veterinarian. If you accidentally give too much, contact your veterinarian immediately.
Cost of Prazosin for Cats
Generic capsules or tablets of prazosin generally cost $15-$25 for a 2-week supply. Liquid forms of the medication that are specially compounded for your cat will cost more based on the fee charged by the pharmacy.
Brand name formulations of prazosin are usually much more expensive, in the range of $150 for a similar 2-week supply.
Prazosin Storage Instructions
Tablets and capsules of prazosin should be stored at room temperature away from direct sunlight. Liquid and compounded forms should be stored according to labeled instructions and may require refrigeration.
All medications should be stored in their original container out of reach of children and pets.