Finasteride

What is finasteride?

Finasteride (brand names Proscar®, Propecia®) is a medication used in dogs to help with infertility issues caused by benign prostatic hypertrophy (an enlargement of the prostate gland caused by hormones) and to treat the general clinical signs associated with it. Finasteride can reduce the size of the prostate without affecting the production of testosterone or the quality of semen in dogs used for breeding.

In intact, non-breeding dogs, finasteride can be used to help with signs related to benign prostatic hypertrophy, such as an increased urge to urinate, straining to defecate, and blood in the urine. Finasteride is also used to treat adrenal disease in ferrets.

Its use in dogs and ferrets is off-label (extra label). Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How is finasteride given?

• Finasteride comes in pill form and is given by mouth.
• DO NOT crush pills, as this creates powder that can become airborne, and inhaling the drug is dangerous.
• It may be given with or without food. If your pet vomits or seems unwell after receiving the medication on an empty stomach, give the next dose with a small amount of food.
• Discontinue finasteride before and during breeding to minimize any potential issues with offspring.

Finasteride is considered a hazardous drug, so it is essential to avoid accidental exposure. Wear gloves when handling the medication and do not handle it if you are pregnant or nursing. If your pet vomits after giving this drug, wear gloves while cleaning up.

This medication can take up to a few weeks before full effects are noted, but gradual improvements are usually noticeable after a few days.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember and then wait the recommended amount of time between doses. However, if it is almost time for the next dose, skip the dose you missed and resume the regular dosing schedule. After that, return to the regular schedule. Do not give the pet two doses at once.

Are there any potential side effects from finasteride?

No side effects have been reported in dogs. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

DO NOT USE finasteride in:

• Dogs that are young/sexually developing
• Female dogs that are sexually mature, pregnant, or nursing
• Dogs that are known to be hypersensitive to it

USE WITH CAUTION in:

• Dogs with significant liver disease

Are there any drug interactions I should be aware of?

There are no documented drug interactions for this medication. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any treatment.

Is any monitoring needed with this medication?

• Your veterinarian should perform prostate exams to determine if the drug is working.
• If used to treat clinical signs, monitor for relief of symptoms. Contact your veterinarian with any changes.

How do I store finasteride?

• Store in a tightly sealed container, protected from light, at room temperature (below 30°C or 86°F).
• Keep the container out of reach of children and pets.

What should I do in case of an emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet's weight and symptoms.