How does this medication work? What will it do for me?

Finasteride belongs to a group of medications known as 5-alpha-reductase inhibitors. Finasteride is used to treat benign prostatic hyperplasia (BPH), also known as enlarged prostate. Finasteride can be used alone or in combination with another medication called doxazosin (an alpha blocker). These medications may be taken together to reduce the progress of your BPH symptoms. If you are taking this combination, be sure to also read the patient information for doxazosin.

This medication improves the symptoms associated with BPH, such as decreased urine flow, difficulty urinating, getting up to urinate during the night, or hesitation at the start of urination. It may take 6 months or more to see the full effects of finasteride. Finasteride reduces the likelihood of prostate surgery for men with BPH. Finasteride must be taken on a regular basis to be effective. If the medication is stopped, the prostate will start to grow again.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each blue, concave apple shaped, film coated tablet, debossed with "A" on one side and "FIN" and "5" on the other side contains 5 mg of finasteride. Nonmedicinal ingredients: lactose monohydrate, cellulose microcrystalline, sodium starch glycolate, starch, pregelatinised (starch 1500), docusate sodium, magnesium stearate, hydroxy propyl cellulose, hypromellose, titanium dioxide, talc, FD&C Blue, and iron oxide yellow.

How should I use this medication?

The recommended adult dose of finasteride is 5 mg once daily, taken with or without food.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Finasteride (for BPH) should not be taken by anyone who:

  • is allergic to finasteride or to any of the ingredients of the medication
  • is a child
  • is a woman

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • decreased interest in sex
  • decreased volume of ejaculate (i.e., semen)
  • erectile dysfunction (impotence)
  • testicular pain

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • breast enlargement, tenderness, lumps, or nipple discharge
  • signs of an allergic reaction including (e.g., skin rash, itchiness, hives, swelling of the lips or tongue)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Breast cancer: Male breast cancer has been reported in a small number of people taking finasteride. It is not known with certainty whether finasteride can cause breast cancer, but this possibility cannot be ruled out at this time. If you notice any changes in your breasts, such as breast enlargement, pain, tenderness, lumps, or nipple discharge, contact your doctor as soon as possible.

Laboratory tests: This medication may decrease PSA levels (a substance normally produced and used to evaluate prostate cancer) and should be taken into account when evaluating PSA levels.

Liver function: Since finasteride is metabolized in the liver, caution should be used by people with reduced liver function.

Long-term use: The effects of using this medication for the long term (i.e., more than 10 years) have not been established.

Prostate cancer: Finasteride (for BPH) may be linked with an increased risk of developing a rare type of cancer called high-grade prostate cancer. The risk of this cancer while taking this medication is still considered very small. Note that finasteride (for BPH) is not approved to treat prostate cancer. If you have any concerns about this medication, talk to your health care provider.

Surgery: People who are candidates for immediate prostate surgery should not take finasteride.

Pregnancy and birth defects: When absorbed into the system of a pregnant woman, finasteride may cause abnormalities of the genitals in a male baby. Crushed or broken finasteride tablets should not be handled by women who are or may become pregnant because finasteride may be absorbed into their system through the skin.

Children: Finasteride should not be used by children.

What other drugs could interact with this medication?

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. In many cases, interactions are intended or are managed by close monitoring. Speak to your doctor about how any drug interactions are being managed or should be managed.