FINASTERIDE

(fin-as'te-ride)

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

Availability

1 mg, 5 mg tablets

Action

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.

Uses

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

Contraindications

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.

Administration

Oral

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.

Interactions

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

Pharmacokinetics

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

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