Commonly reported side effects of finasteride include: impotence and decreased libido. See below for a comprehensive list of adverse effects.

Applies to finasteride: oral tablet

Along with its needed effects, finasteride may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking finasteride:

More common

• Chills
• cold sweats
• confusion
• dizziness, faintness, or lightheadedness when getting up from a lying or sitting position

Less common

• Bloating or swelling of the face, arms, hands, lower legs, or feet
• breast enlargement and tenderness
• hives or welts
• itchy skin
• rapid weight gain
• redness of the skin
• skin rash
• swelling of the lips and face
• tingling of the hands or feet
• unusual weight gain or loss

Incidence not known

• Clear or bloody discharge from the nipple
• dimpling of the breast skin
• inverted nipple
• lump in the breast or under the arm
• persistent crusting or scaling of the nipple
• redness or swelling of the breast
• sore on the skin of the breast that does not heal

Some side effects of finasteride may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

• Decreased interest in sexual intercourse
• inability to have or keep an erection
• loss in sexual ability, desire, drive, or performance

Less common

• Runny nose
• sleepiness or unusual drowsiness
• sneezing
• stuffy nose

Less common or rare

• Abdominal or stomach pain
• back pain
• decreased amount of semen
• diarrhea
• dizziness
• headache

Incidence not known

• Testicular pain

Applies to finasteride: oral tablet

Most men were older and were taking concomitant medications and/or had comorbid conditions:

Very common (10% or more): Impotence (up to 18.5%)

Common (1% to 10%): Abnormal ejaculation, decreased ejaculatory volume, abnormal sexual function, gynecomastia, erectile dysfunction, ejaculation disorder, testicular pain, male infertility and/or poor seminal quality

Two hundred fourteen reports of gynecomastia in men taking finasteride in the United States were received by the FDA between June 1992 and February 1995. Among those reported, fifty eight percent were taking additional medications that have been associated with gynecomastia. Sixty nine of 86 patients who discontinued finasteride treatment had partial or complete remission.

New reports of drug-related sexual adverse experiences have been reported to decrease with duration of therapy.

Erectile dysfunction has been reported to continue beyond treatment discontinuation. Normalization or improvement of seminal quality has been reported after withdrawing finasteride treatment.

Finasteride may cause a decrease in PSA levels in patients with benign prostatic hyperplasia as well as in patients with prostate cancer. In one study, mean PSA reductions of 50% were noted, regardless of baseline levels. There was no indication that PSA levels were further suppressed in patients with prostate cancer.

PSA levels are commonly used in the screening process for prostate cancer. Patients who develop sustained increases in PSA while on finasteride therapy should be carefully evaluated for medical causes as well as noncompliance.

Uncommon (0.1% to 1%): Breast tenderness, breast enlargement

Frequency not reported: Reductions in prostate specific antigen (PSA) levels of approximately 50%

Common (1% to 10%): Decreased libido, dizziness, somnolence

Frequency not reported: Headache

Common (1% to 10%): Postural hypotension, hypotension

Postmarketing reports: Palpitations

Frequency not reported: A prevention or delay in the appearance of prostate cancer, an increased risk of high-grade prostate cancer

Postmarketing reports: Rare cases of male breast cancer

Frequency not reported: Nausea, flatulence, abdominal pain

A 58 year old man presented with an itchy, lumpy rash on upper and lower extremities following two weeks of finasteride treatment for prostatism. The patient had no known allergies and was taking no other medications prior to the episode. The finasteride was discontinued and dapsone was initiated. The rash resolved two weeks after finasteride therapy was stopped.

Rare (less than 0.1%): Rash

Very rare (less than 0.01%): Cutaneous leukocytoclastic vasculitis, solitary fixed drug eruption

Postmarketing reports: Pruritus, urticaria, angioedema (including swelling of the lips, tongue, throat, and face)

Frequency not reported: Pruritus, urticaria, angioedema of the lips, tongue, throat, and face

Common (1% to 10%): Edema

Uncommon (0.1% to 1%): Rhinitis, dyspnea

Frequency not reported: Depression

Frequency not reported: Asthenia

Frequency not reported: Increased hepatic enzymes