Propecia, Proscar
Classifications: hormone; antiandrogen; 5-alpha reductase inhibitor;
Therapeutic: antiandrogen

Pregnancy Category: X


1 mg, 5 mg tablets


Specific inhibitor of the steroid 5-alpha-reductase, an enzyme necessary to convert testosterone into the potent androgen 5-alpha-dihydrotestosterone (DHT) in the prostate gland.

Therapeutic Effect

Decreases the production of testosterone in the prostate gland.


Benign prostatic hypertrophy, male pattern hair loss (androgenetic alopecia).


Hypersensitivity to finasteride; pregnancy (category X), lactation, females, and children.

Cautious Use

Hepatic impairment, obstructive uropathy.

Route & Dosage

Benign Prostatic Hypertrophy
Adult: PO 5 mg/d

Male Pattern Hair Loss
Adult: PO 1 mg q.d.


  • Crush tablets if necessary. Pregnant women should not handle the crushed drug; if absorbed through the skin it may be harmful to a male fetus.
  • Store at 15°–30° C (59°–86° F) unless otherwise directed.

Adverse Effects (≥1%)

Urogenital: Impotence, decreased libido, decreased volume of ejaculate.

Diagnostic Test Interference

Depresses levels of DHT and prostate-specific antigen (PSA). Testosterone levels usually are increased.


Drug: No clinically significant interactions established. Herbal: Saw palmetto may potentiate effects of finasteride.


Absorption: Readily from GI tract. Onset: 3–6 mo. Duration: 5–7 d. Elimination: 39% in urine, 57% in feces. Half-Life: 5–7 h.

Nursing Implications

Assessment & Drug Effects

  • Evaluate carefully any sustained increase in serum PSA levels while patient is taking finasteride. It may indicate the presence of prostate cancer or noncompliance with the therapy.
  • Monitor patients with a large residual urinary volume or decreased urinary flow. These patients may not be candidates for this therapy.

Patient & Family Education

  • Use a barrier contraceptive to prevent pregnancy in a sexual partner.
  • Be aware that impotence and decreased libido may occur with treatment.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2022 Last Updated On: 10/03/2022 (0)
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