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Finasteride is a drug that belongs to the class of androgen inhibitors, which means that it blocks the production of male sex hormones. It is sold in the United States and Canada under the brand names Proscar and Propecia.


Finasteride has two main purposes: the treatment of urinary problems in men caused by benign prostatic hypertrophy (BPH) or enlargement of the prostate gland; and the stimulation of new hair growth in men with male pattern baldness. Finasteride was first approved by the Food and Drug Administration (FDA) in 1992 under the trade name Proscar as a treatment for BPH. It received a second FDA approval in December 1997 under the trade name Propecia for the treatment of hair loss in men. Finasteride has also been used by some European doctors to treat hair loss in postmenopausal women, although its use in women is considered controversial in the United States. It is considered the most effective nonsurgical treatment for male pattern baldness as of 2005.
Finasteride works to relieve such symptoms of prostate enlargement as urinary urgency, the need to urinate frequently at night (nocturia), inability to completely empty the bladder, incontinence, or painful urination (dysuria) by blocking the production of DHT. DHT causes the prostate gland to grow and increase pressure on the bladder. As the swollen prostate gradually shrinks, the patient finds it easier to pass urine without discomfort and to empty the bladder completely before going to sleep. Some doctors also prescribe finasteride as pretreatment for prostate surgery, as it lowers the risk of severe bleeding during the operation.
As of early 2005, the National Cancer Institute (NCI) was evaluating finasteride as a possible chemo preventative for prostate cancer in selected patients. Researchers were not yet certain, however, which men might benefit most from taking the drug.


Finasteride inhibits the body's production of an enzyme called 5-alpha-reductase, which is needed to convert testosterone to another androgen called 5-alpha-dihydrotestosterone (DHT). Finasteride is a white powder that can be dissolved in alcohol or chloroform but is very difficult to dissolve in water. Both Proscar and Propecia are manufactured as coated tablets to be taken by mouth.

Recommended dosage

  • Proscar: Finasteride for treatment of an enlarged prostate is taken once a day as a 5-mg tablet. The pill may be crushed or broken if the patient finds it hard to swallow.
  • Propecia: Finasteride for hair regrowth is taken once a day as a 1-mg tablet. The drug may be taken with or without meals, as the patient prefers.


Finasteride should be stored in dry places and should be kept at a temperature between 59°F and 86°F (15-30°C). Heat and moisture may cause the drug to lose its potency.
The drug can be safely handled by pregnant women as long as the tablets are intact; however, crushed or broken tablets should not be touched by a pregnant woman as the drug can be absorbed through the skin. If the woman is carrying a male fetus, the drug can cause abnormalities in the baby's sex organs. The FDA issued a warning in 2003 that men taking finasteride should not donate blood until one month after the final dose of the drug, on the grounds that their blood could contain high enough levels of the medication to cause birth defects in a male baby if given to a pregnant woman.
Patients should be advised that finasteride takes several months to reach its full effect—as long as six months for BPH and three months for hair regrowth. In addition, the drug's effects on the body are not permanent; the prostate will start to enlarge again or the hair growth will be lost if the patient stops taking the drug.
Proscar can affect the results of a prostate-specific antigen (PSA) test for cancer of the prostate. Between 30 and 50 percent of men taking the drug will have elevated levels of PSA in their blood serum.
Finasteride should be used cautiously by men with liver disorders.

Side effects

As of 2005 reported side effects from using finasteride include:
  • impotence or loss of interest in sex
  • lumps or pain in the breast or a discharge from the nipple
  • skin rash, itching, or hives
  • swelling of the lips or face
  • a smaller quantity of ejaculate during intercourse (which does not affect fertility)
  • headaches, dizziness, or diarrhea
  • pain in the testicles
These side effects are more common with the 5-mg dose, but usually go away as soon as the drug is discontinued.


As of 2005 finasteride has not been reported to cause significant interactions with other medications.

Key terms

Alopecia — The medical term for baldness.
Androgens — A group of hormones that produces masculine characteristics.
Chemo preventative — Description of a drug given in order to prevent the development of a specific disease. Finasteride was in 2005 being evaluated as a possible cancer chemo preventative.
Dysuria — Painful or difficult urination.
Incontinence — Inability to control urination or defecation.
Nocturia — Excessive need to urinate at night.
Prostate — A gland in males below the bladder that surrounds the urethra. Enlargement of the prostate may cause problems in urination.
Urgency — A sudden and powerful need to urinate.



"Alopecia (Baldness)." Section 10, Chapter 116 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, and Robert Berkow. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
"Benign Prostatic Hyperplasia (Benign Prostatic Hypertrophy)." Section 17, Chapter 218 in The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers and Robert Berkow. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
Wilson, Billie A., et al. Nurses Drug Guide 2000, Stamford, CT: Appleton & Lange, 2000.


Arca, E., G. Acikgoz, H. B. Tastan, et al. "An Open, Randomized, Comparative Study of Oral Finasteride and 5% Topical Minoxidil in Male Androgenetic Alopecia." Dermatology 209 (2004): 117-125.
Crea, G., G. Sanfilippo, G. Anastasi, et al. "Pre-Surgical Finasteride Therapy in Patients Treated Endoscopically for Benign Prostatic Hyperplasia." Urologia Internationalis 74 (January 2005): 51-53.
Haber, R. S. "Pharmacologic Management of Pattern Hair Loss." Facial Plastic Surgery Clinics of North America 12 (May 2004): 181-89.
Parnes, H. L., I. M. Thompson, and L. G. Ford. "Prevention of Hormone-Related Cancers: Prostate Cancer." Journal of Clinical Oncology 23 (January 10, 2005): 368-77.
Trueb, R. M., and the Swiss Trichology Group. "Finasteride Treatment of Patterned Hair Loss in Normoandrogenic Postmenopausal Women." Dermatology 209 (2004): 202-07.


American Society of Health-System Pharmacists (ASHP). 7272 Wisconsin Avenue, Bethesda, MD 20814. (301)657-3000.
United States Food and Drug Administration (FDA). 5600 Fishers Lane, Rockville, MD 20857-0001. (888) INFO-FDA.


Food and Drug Administration (FDA) Medication Deferral List, December 9, 2003. 〈〉.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


Propecia, Proscar

Pharmacologic class: Androgen inhibitor

Therapeutic class: Sex hormone, hair regrowth stimulant

Pregnancy risk category X


Suppresses dihydrotestosterone levels by inhibiting the hepatic enzyme 5-alpha reductase, which converts testosterone to dihydrotestosterone in prostate, liver, and skin


Tablets: 1 mg (Propecia), 5 mg (Proscar)

Indications and dosages

Symptomatic benign prostatic hypertrophy (BPH)

Adults: 5 mg P.O. daily

To reduce risk of progression of BPH symptoms

Adults: 5 mg P.O. daily (Proscar) given with doxazosin

Male-pattern baldness

Adults: 1 mg P.O. daily

Off-label uses

• Acne in women

• Hirsutism


• Hypersensitivity to drug or its components

• Pregnant patients, women who may potentially be pregnant


Use cautiously in:

• hepatic impairment, obstructive uropathy, increased risk of high-grade prostate cancer, decrease in serum prostate-specific antigen (PSA) level

• women (not indicated)

• children (not indicated).


• Give with or without food.

• Know that female patients who are or may be pregnant shouldn't handle crushed or broken tablets. (Tablets are coated, so handling of intact tablets doesn't pose a problem.)

Adverse reactions

CNS: dizziness, headache, asthenia

EENT: lip swelling

GU: erectile dysfunction, decreased ejaculate volume, decreased libido, testicular pain, gynecomastia

Musculoskeletal: back pain

Skin: rash


Drug-drug. Theophylline: increased theophylline clearance

Drug-diagnostic tests. PSA: 50% decrease

Patient monitoring

• Carefully evaluate sustained PSA increases during therapy.

• Monitor fluid intake and output closely.

Patient teaching

• Tell patient he may take drug with or without food.

• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.

• Inform patient that he may experience erectile dysfunction and decreased ejaculate. Advise him to discuss these issues with prescriber.

• Caution female caregiver or companion who is or may be pregnant not to handle crushed or broken tablets.

• Tell patient he may need at least 6 months of therapy for BPH treatment and at least 3 months to see improvement in male-pattern baldness.

• Inform patient with BPH that he'll undergo periodic digital rectal exams.

• Instruct patient not to donate blood for at least 1 month after last dose.

• As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs and tests mentioned above.

McGraw-Hill Nurse's Drug Handbook, 7th Ed. Copyright © 2013 by The McGraw-Hill Companies, Inc. All rights reserved


A synthetic androgen inhibitor used primarily in men for the treatment of benign prostatic hyperplasia and androgenetic alopecia.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Proscar®, Propecia Hair A competitive inhibitor of 5α-reductase, the enzyme responsible for converting testosterone to DHT or dihydrotestosterone; it is used to ↓ BPH Sx–↓ obstructive Sx, ↓ prostate volume, ↑ urinary flow–reportedly less effective than Hytrin; it binds with 5α-reductase type 2, inhibiting production of DHT; its uses include reversal of male-pattern baldness, hirsutism, acne Adverse effects ↓ Libido, impotence, ejaculatory defects. See Androgen ablation therapy.
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


An anti-androgen drug used to reduce prostate enlargement in benign prostatic hypertrophy by inhibiting the enzyme 5-alpha reductase which is concerned in the conversion of TESTOSTERONE to dihydrotestosterone, the main prostate androgen. Like all testosterone antagonists this drug can cause reduced sexual interest, impotence, ejaculation problems, breast tenderness and breast enlargement (gynecomastia). In a trial involving nearly 19,000 men the drug was found to reduce the incidence of prostate cancer by a quarter. It may, however, increase the risk of high-grade cancers. A brand name is Proscar.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
Researchers found that, although finasteride was associated with a reduced risk of prostate cancer overall, the risk of high-grade prostate cancer was slightly higher among men given the drug.
A patient's comorbidities can help tailor which treatments to use, so if a patient with HS also has androgenetic alopecia, finasteride can be considered, while spironolactone, with or without an OC, can be considered for a patient with acne--and metformin can be considered for a patient with diabetes or prediabetes, or polycystic ovary syndrome (PCOS), she commented.
[USA], May 20 ( ANI ): Finasteride, a common hormone-blocking drug, does not increase risk of prostate cancer death, finds a study.
Though the two studies described utilized GnRH analogues, there are many other treatment modalities being investigated including ketoconazole, finasteride, anti-androgens, PDE5 inhibitors, pseudoephedrine, terbutaline, and digoxin (4).
Finasteride is a prescription-only treatment that isn't available on the NHS, but pharmacies are able to sell it without prescription by insisting customers are seen by a pharmacist first before being sold the drug.
Finasteride and dutasteride, both 5-alpha reductase inhibitors, are considered first-line treatment for androgenetic hair loss in men and used increasingly in women.
Patients were divided into 2 groups: those who were given topical finasteride 0.5% and those who were given placebo solution on a daily basis for 5 days before each session.
Pharmaceutical company Mylan NV (NasdaqMYL) TASE:MYL) stated on Monday that it has introduced Finasteride Tablets USP, 1 mg in the US market.
In a recent study, Euromed's branded CO2 supercritical saw palmetto extract (Prosterol) was found to work in the same way and just as well as the original prescription drug standard for treating enlarged prostate in men (finasteride).
Finasteride and dutasteride are approved for pattern hair loss in men, but not in women.
With respect to trials assessing androgen blockers in men to prevent prostate cancer, the Prostate Cancer Prevention Trial is assessing the use of finasteride in men aged 55years and older.
They include donepezil, vitamin D (50,000 IU), pioglitazone, finasteride and escitalopram.