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Proscar Side Effects

Generic name: finasteride

Medically reviewed by Drugs.com. Last updated on Oct 9, 2023.

Note: This document contains side effect information about finasteride. Some dosage forms listed on this page may not apply to the brand name Proscar.

Applies to finasteride: oral tablet.

Serious side effects of Proscar

Along with its needed effects, finasteride (the active ingredient contained in Proscar) 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

Less common

Incidence not known

Other side effects of Proscar

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

Less common

Less common or rare

Incidence not known

For Healthcare Professionals

Applies to finasteride: oral tablet.

Genitourinary

Two hundred fourteen reports of gynecomastia in men taking finasteride (the active ingredient contained in Proscar) 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.[Ref]

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

Postmarketing reports: Hematospermia[Ref]

Endocrine

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

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

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.[Ref]

Nervous system

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

Frequency not reported: Headache[Ref]

Cardiovascular

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

Postmarketing reports: Palpitations[Ref]

Oncologic

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[Ref]

Gastrointestinal

Frequency not reported: Nausea, flatulence, abdominal pain[Ref]

Dermatologic

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)[Ref]

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.[Ref]

Hypersensitivity

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

Metabolic

Common (1% to 10%): Edema[Ref]

Respiratory

Uncommon (0.1% to 1%): Rhinitis, dyspnea[Ref]

Psychiatric

Frequency not reported: Depression

Musculoskeletal

Frequency not reported: Asthenia

Hepatic

Frequency not reported: Increased hepatic enzymes

References

1. Gormley GJ, Stoner E, Bruskewitz RC, Imperato-McGinley J, Walsh PC, McConnell JD, Andriole GL, Geller J, Bracken BR, Tenover JS, et al. The effect of finasteride in men with benign prostatic hyperplasia. The Finasteride Study Group. N Engl J Med. 1992;327:1185-91.

2. Steiner JF. Finasteride: a 5 alpha-reductase inhibitor. Clin Pharm. 1993;12:15-23.

3. Product Information. Proscar (finasteride). Merck & Co., Inc. 2002.

4. Tammela TL, Kontturi MJ. Urodynamic effects of finasteride in the treatment of bladder outlet obstruction due to benign prostatic hyperplasia. J Urol. 1993;149:342-4.

5. Guess HA, Heyse JF, Gormley GJ. The effect of finasteride on prostate-specific antigen in men with benign prostatic hyperplasia. Prostate. 1993;22:31-7.

6. Stoner E, Round E, Ferguson D, Gormley GJ. Clinical experience of the detection of prostate cancer in patients with benign prostatic hyperplasia treated with finasteride. J Urol. 1994;151:1296-300.

7. Volpi R, Maccarini PA, Boni S, Chiodera P, Coiro V. Finasteride-induced gynecomastia in a 62-year-old man. Am J Med Sci. 1995;309:322-5.

8. Guess HA, Gormley GJ, Stoner E, Oesterling JE. The effect of finasteride on prostate specific antigen: review of available data. J Urol. 1996;155:3-9.

9. Stoner E. 5 alpha-reductase inhibitors/finasteride. Prostate. 1996;Suppl 6:82-7.

10. Green L, Wysowski DK, Fourcroy JL. Gynecomastia and breast cancer during finasteride therapy. N Engl J Med. 1996;335:823.

11. Ferrando J, Grimalt R, Alsina M, Bulla F, Manasievska E. Unilateral Gynecomastia Induced by Treatment With 1 mg of Oral Finasteride. Arch Dermatol. 2002;138:543-4.

12. Thompson IM, Goodman PJ, Tangen CM, et al. The influence of finasteride on the development of prostate cancer. N Engl J Med. 2003;349:215-24.

13. Australian Government. Department of Health. Therapeutic Goods Administration. Medicines Safety Update, Volume 4, Number 6, December 2013. http://www.tga.gov.au/hp/msu-2013-06.htm 2013.

14. Lear JT, Byrne JPH. Finasteride-related cutaneous vaculitis. Postgrad Med J. 1996;72:127.

15. Oyama N, Kaneko F. Solitary fixed drug eruption caused by finasteride. J Am Acad Dermatol. 2009;60:168-9.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.