By Rania Gollakner, BS, DVM, MPH

What is finasteride?

finasteride_2Finasteride (brand names: Proscar®, Propecia®) is a medication used in dogs to restore infertility issues caused by benign prostatic hypertrophy (an enlargement of the prostate gland caused by hormones) and treat the general clinical signs associated with it. Finasteride is a hormone antagonist, which stops testosterone from being converted to dihydrotestosterone, the hormone that stimulates prostate growth. Stopping the conversion of testosterone to dihydrotestosterone 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 increased urge to urinate, straining to defecate, and blood in the urine.

How do I give my pet finasteride?

Finasteride comes in pill form and is given orally (by mouth). It may be given with or without food.

Finasteride should be temporarily discontinued prior to and during breeding to minimize any potential issues with offspring.

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

What if I miss giving my pet the medication?

Give the missed dose as soon as you remember, and then wait the recommended amount of time between doses. Never give your pet two doses at once or give extra doses.

Are there any potential side effects from finasteride?

No side effects have been reported in dogs.

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?

In dogs: Young/sexually developing animals should not be given this medication, nor should it be given to sexually mature or pregnant females. It should not be given to dogs that are known to be hypersensitive to finasteride, or dogs who have liver failure.

In humans: Finasteride is a known teratogen that can be absorbed through the skin, so it should not be handled by pregnant or potentially pregnant women. Women hoping to become pregnant should also avoid the sperm of male partners exposed to finasteride.


Are there any drug interactions I should be aware of?

No drug interactions with Finasteride have been reported. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Prostate exams should be done to determine if the drug is working. If using to treat clinical signs, monitor for relief of symptoms.

How do I store finasteride?

Store in a tightly sealed container, protected from light, at room temperature.


What should I do in case of 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.

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