Generic Name: finasteride

Brand Names: Propecia, Proscar

Uses

Benign Prostatic Hypertrophy (BPH)

Treatment of symptomatic BPH to improve symptoms and reduce the risk of acute urinary retention and the need for surgery. Ineffective in patients who do not have evidence of prostatic enlargement.

Used alone or in combination with an α₁-adrenergic blocking agent (e.g., doxazosin). Combination therapy with a 5α-reductase inhibitor and an α₁-blocker has been more effective than therapy with either drug alone in preventing long-term BPH symptom progression. Men at risk for BPH progression are most likely to benefit from combination therapy.

Steroid 5α-reductase inhibitors may be a useful alternative to surgery in patients with obstructive manifestations who are awaiting or unwilling to undergo surgical correction of BPH; may aid those who are at increased risk from or are not candidates for prostate surgery. Also may be considered in patients who have symptomatic prostatic enlargement but whose symptoms are not bothersome (i.e., do not interfere with activities of daily living) in order to prevent progression of the disease.

Although drug therapy usually is not as effective as surgical therapy, it may provide adequate symptomatic relief with fewer and less serious adverse effects compared with surgery.

Androgenetic Alopecia

Stimulates regrowth of hair in men with mild to moderate androgenetic alopecia (male pattern alopecia, hereditary alopecia, common male baldness).

Effective in promoting hair regrowth in young and middle-aged men (18–41 years of age) with mild to moderate androgenetic alopecia and hair loss on the vertex of the scalp and/or anterior mid-scalp area; the effects on bitemporal recession are not established.

Recommended only for use in men; not indicated for use in women or children. Ineffective for treatment of hair loss in postmenopausal women with androgenetic alopecia.

Withdrawal of the drug leads to reversal of clinical benefit within 1 year. Therapy must be continued to sustain initial regrowth and subsequent slowing of hair loss. Maximum improvement in hair count occurs during first 2 years of therapy.

Dosage and Administration

Administration

Administer orally without regard to meals.

Dosage

Adults

BPH

Oral

5 mg once daily, alone or in combination with doxazosin mesylate.

While early symptomatic improvement may occur, ≥6 months of therapy may be necessary to determine clinical benefit.

Androgenetic Alopecia

Oral

1 mg once daily.

Generally administered for ≥3 months before benefit is observed. If improvement does not occur within 1 year, further treatment with the drug is unlikely to provide benefit.

Continued use recommended to sustain benefit, which should be re-evaluated periodically.

Discontinuance leads to reversal of effect within 12 months.

Special Populations

Hepatic Impairment

No specific dosage recommendations for hepatic impairment. (See Hepatic Impairment under Cautions.)

Renal Impairment

Dosage adjustment not required.

Geriatric Patients

Dosage adjustment not required.

Cautions

Contraindications

• Known or suspected pregnancy. (See Fetal/Neonatal Morbidity and also Pregnancy under Warnings/Precautions.)
• Known hypersensitivity to finasteride or any ingredient in the formulation.

Warnings/Precautions

Warnings

Fetal/Neonatal Morbidity

May cause fetal harm; teratogenicity demonstrated in animals.

Animal studies indicate adverse effects on embryofetal development of male fetuses exposed to the drug during pregnancy (e.g., abnormalities of the external genitalia, decreased prostatic and seminal vesicular weights, delayed preputial separation, and transient nipple development).

No abnormalities were observed in female offspring exposed to any finasteride dosage in utero.

Because of the potential for absorption through the skin and the subsequent potential risk to a male fetus, pregnant women or women who potentially may be pregnant should avoid direct contact with broken (e.g., crushed) tablets of the drug.

If used during pregnancy or if pregnancy occurs, apprise the pregnant woman of potential fetal hazard to the male fetus.

General Precautions

Patient Assessment

Evaluate candidates for finasteride therapy for other urologic conditions that might mimic BPH, such as infection, prostate cancer, stricture disease, hypotonic bladder, other neurogenic disorders.

Perform digital rectal examinations, as well as other screening tests for prostate cancer before initiating therapy for BPH and periodically thereafter.

Monitor patients with a large residual urinary volume and/or severely diminished urinary flow carefully for obstructive uropathy. Such patients may not be candidates for finasteride therapy.

Prostate Cancer

No clinical benefit has been demonstrated in patients with prostate cancer.

No effect on rate of prostate cancer detection in clinical studies in patients with BPH and elevated serum PSA concentrations.

Prostate-specific Antigen (PSA)

Decreases PSA concentrations; may interfere with interpretation of serum PSA determinations. (See Specific Drugs and Laboratory Tests under Interactions.)

Carefully evaluate sustained increases in serum PSA concentration during finasteride therapy, including consideration that the patient is not compliant.

Breast Changes

Breast enlargement and tenderness reported in men receiving finasteride 5 mg daily for BPH or 1 mg daily for androgenetic alopecia.

Breast neoplasm was reported in several men receiving finasteride 5 mg daily (alone or in combination with doxazosin) in a clinical trial of 4–6 years’ duration; however, breast neoplasm was reported in placebo recipients only in another long-term trial of finasteride. Not known whether a causal relationship exists between long-term finasteride use and breast neoplasia in men.

Specific Populations

Pregnancy

Category X. (See Fetal/Neonatal Morbidity and also Contraindications under Cautions.)

Lactation

Not known whether finasteride is distributed into milk, but the drug is not indicated for use in women.

Pediatric Use

Safety and efficacy not established, but the drug is not indicated for use in children.

Geriatric Use

No substantial differences in safety and efficacy for treatment of BPH in men ≥65 or ≥75 years of age relative to younger men. Efficacy for promoting hair regrowth in geriatric men with androgenetic alopecia not established.

Hepatic Impairment

Not studied in patients with hepatic impairment. Extensively metabolized in the liver. Use with caution.

Common Adverse Effects

Impotence, decreased libido, ejaculation disorder (e.g., decreased volume of ejaculate), breast enlargement.

Interactions

Extensively metabolized by CYP3A4; apparently does not affect CYP isoenzymes.

Specific Drugs and Laboratory Tests

Pharmacokinetics

Absorption

Bioavailability

Mean bioavailability is 63–65%.

Onset

Rapid, with maximum decrease in serum DHT concentrations at 8 hours following oral administration of first dose of 5 mg, and 65% suppression of serum DHT within 24 hours after oral administration of 1 mg.

Duration

DHT suppression maintained throughout 24-hour dosage interval; DHT decreased by about 70% with 5-mg daily dosage for at least 4 years.

Food

Food does not appear to affect absorption.

Distribution

Extent

Crosses blood-brain barrier, but is not preferentially distributed into CSF.

Distributed into semen in amounts estimated to be 50- to 100-fold less than the dose (5 mcg) that had no effect on circulating DHT concentrations in men.

Crosses the placenta in rats.

Not known whether distributed into human milk.

Plasma Protein Binding

Approximately 90%.

Elimination

Metabolism

Extensively metabolized, principally in the liver, via CYP3A4; 2 metabolites identified with ≤20% of activity of finasteride.

Elimination Route

Principally excreted in the feces (57%) and in urine (39%) as metabolites.

Half-life

Males 18–60 years of age: 5–6 hours.

Special Populations

Half-life in males ≥70 years of age: 8 hours; increase not clinically important.

Effect of hepatic impairment on pharmacokinetics not studied; extensively metabolized in the liver.

In patients with chronic renal impairment (Cl_cr 9–55 mL/minute), pharmacokinetics after single-dose administration appear to be similar to those in healthy individuals except that the proportion excreted in feces versus urine is increased in those with impairment.

Stability

Storage

Oral

Tablets

5-mg tablets: Tight, light resistant containers at room temperature <30°.

1-mg tablets: Tight, light resistant containers at 15–30°C.

Actions

• Competitive specific inhibitor of type 2 isoenzyme of steroid 5α-reductase.
• 100-fold more selective for type 2 5α-reductase than for type 1 isoenzyme; chronic treatment may have some effect on the type 1 isoenzyme.
• Type 2 steroid 5α-reductase isoenzyme converts testosterone to DHT in the prostate gland, seminal vesicles, epididymides, liver, and the inner root sheath of hair follicles and is responsible for the formation of about two-thirds of circulating DHT.
• Reduces serum and tissue (e.g., prostate, scalp) DHT concentrations substantially.
• Increases serum testosterone concentrations minimally to moderately (usually within the normal range) and prostatic testosterone concentrations substantially.
• Decreases prostatic volume by an average of about 20–30% after 6–24 months of continued therapy in most patients with BPH.
• In men with androgenetic alopecia, decreases scalp DHT concentrations to levels found in hairy scalp, reduces serum DHT, increases hair regrowth, and slows hair loss. However, exact mechanism of action not fully elucidated.

Advice to Patients

• Importance of obtaining and reading patient information on finasteride before initiation of therapy and with each new prescription refill.
• Importance of advising pregnant women or women who may be pregnant to avoid direct contact with broken or crushed tablets of the drug. (See Fetal/Neonatal Morbidity under Cautions.)
• Importance of pregnant women informing a clinician if they swallow the drug or have skin contact from handling broken or crushed finasteride tablets; necessity for clinicians to advise pregnant women of risk to male fetus.
• Advise patients that a decrease in the volume of ejaculate may occur but that this does not appear to interfere with normal sexual function.
• Advise patients of the possibility of impotence and decreased libido.
• Importance of promptly informing clinician of any changes in breasts (e.g., lumps, pain, nipple discharge), since breast changes (enlargement, tenderness, neoplasm) have been reported.
• Advise that ≥6 months of continuous therapy may be required before improvement in BPH symptoms occurs and a decrease in prostate size may not noticeably improve urine flow or symptoms.
• Advise that ≥3 months of continuous therapy may be required before improvement in androgenetic baldness occurs, and if no improvement is observed after 12 months, further treatment is unlikely to be of benefit.
• Advise that hair growth gained during treatment for androgenetic baldness will likely be lost within 12 months after discontinuing the drug.
• Importance of informing clinician about finasteride therapy if a PSA test is performed.
• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.
• Importance of advising patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Comparative Pricing

This pricing information is subject to change at the sole discretion of DS Pharmacy. This pricing information was updated 09/2009. For the most current and up-to-date pricing information, please visit www.drugstore.com. Actual costs to patients will vary depending on the use of specific retail or mail-order locations and health insurance copays.

AHFS Drug Information. © Copyright, 1959-2009, Selected Revisions May 2007. American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland 20814.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.