Skip to Content

Finasteride

Pronunciation

Pronunciation

(fi NAS teer ide)

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Tablet, Oral:

Propecia: 1 mg

Proscar: 5 mg [contains fd&c blue #2 aluminum lake]

Generic: 1 mg, 5 mg

Brand Names: U.S.

  • Propecia
  • Proscar

Pharmacologic Category

  • 5 Alpha-Reductase Inhibitor

Pharmacology

Finasteride competitively inhibits type II 5-alpha reductase, resulting in inhibition of the conversion of testosterone to dihydrotestosterone and markedly suppresses serum dihydrotestosterone levels

Distribution

Vdss: 76 L

Metabolism

Hepatic (extensive) via CYP3A4; two active metabolites (<20% activity of finasteride)

Excretion

Feces (57%) and urine (39%; as metabolites)

Time to Peak

Serum: 1 to 2 hours

Duration of Action

Dihydrotestosterone levels return to normal within 14 days of discontinuation of treatment; prostate volume returns to baseline within ~3 months after discontinuation

Half-Life Elimination

5 to 6 hours (range: 3 to 16 hours); Elderly (≥70 years): 8 hours (range: 6 to 15 hours)

Protein Binding

~90%

Special Populations: Renal Function Impairment

Urinary excretion of metabolites was decreased in patients with renal impairment. This decrease was associated with an increase in fecal excretion of metabolites. Plasma concentrations of metabolites were significantly higher in patients with renal impairment (based on a 60% increase in total radioactivity AUC).

Special Populations: Elderly

Mean AUC0-24 increases 15%.

Use: Labeled Indications

Androgenetic alopecia (Propecia): Treatment of male pattern hair loss in men only.

Limitations of use: Efficacy in bitemporal recession has not been established; not indicated for use in women.

Benign prostatic hyperplasia (Proscar): Treatment (monotherapy) of symptomatic benign prostatic hyperplasia (BPH) to improve symptoms, reduce the risk of acute urinary retention, and to reduce the risk of need for BPH-related surgery); used in combination with an alpha-blocker (doxazosin) to reduce the risk of symptomatic progression.

Limitations of use: Not approved for the prevention of prostate cancer.

Use: Unlabeled

Treatment of female hirsutism

Contraindications

Hypersensitivity to finasteride or any component of the formulation; pregnancy or women of childbearing potential

Dosing: Adult

Benign prostatic hyperplasia (Proscar): Males: Oral: 5 mg once daily (either as a single agent or in combination with doxazosin); early responses may occur although 6 months of treatment is usually needed to assess benefit.

Male pattern baldness (Propecia): Males: Oral: 1 mg once daily; may take 3 months or longer of daily use for observed benefit; continued use is recommended to sustain benefit.

Female hirsutism, idiopathic (off-label use): Females: Oral: 5 mg once daily (Beigi, 2004; Lumachi, 2003; Moghetti, 2000) or 2.5 mg once daily (Tartagni 2004).

Female hirsutism, related to polycystic ovary syndrome (off-label use): Females: Oral: 5 mg once daily (Beigi 2004; Moghetti 2000) or 2.5 mg once daily (Tartagni 2004).

Dosing: Geriatric

Refer to adult dosing.

Dosing: Renal Impairment

No adjustment is necessary.

Dosing: Hepatic Impairment

Use with caution (finasteride is metabolized extensively in the liver)

Administration

May be administered with or without meals. Women of childbearing age should not touch or handle crushed or broken tablets.

Hazardous agent; use appropriate precautions for handling and disposal (NIOSH 2014 [group 3]).

Storage

Propecia: Store at 15°C to 30°C (59°F to 86°F). Keep container tightly closed and protect from moisture.

Proscar: Store below 30°C (86°F). Protect from light. Keep container tightly closed.

Drug Interactions

There are no known significant interactions.

Test Interactions

PSA levels decrease in treated patients. After 6 months of therapy, PSA levels stabilize to a new baseline that is ~50% of pretreatment values. If following serial PSAs in a patient, re-establish a new baseline after ≥6 months of use.

Adverse Reactions

Note: “Combination therapy” refers to finasteride and doxazosin.

>10%:

Cardiovascular: Orthostatic hypotension (combination therapy 18%; monotherapy 9%)

Central nervous system: Dizziness (combination therapy 23%; monotherapy 7%)

Endocrine & metabolic: Decreased libido (combination therapy 12%; monotherapy 2% to 10%)

Genitourinary: Impotence (combination therapy 23%; monotherapy 5% to 19%), ejaculatory disorder (combination therapy 14%; monotherapy <1% to 7%)

Neuromuscular & skeletal: Weakness (combination therapy 17%; monotherapy 5%)

1% to 10%:

Cardiovascular: Edema (combination therapy 3%; monotherapy 1%)

Central nervous system: Drowsiness (combination therapy 3%; monotherapy 2%)

Dermatologic: Skin rash (monotherapy 1%)

Endocrine & metabolic: Gynecomastia (monotherapy 1% to 2%)

Genitourinary: Decreased ejaculate volume (monotherapy 2% to 4%), breast tenderness (monotherapy ≤1%)

Respiratory: Dyspnea (combination therapy 2%; monotherapy 1%), rhinitis (combination therapy 2%; monotherapy 1%)

<1% (Limited to important or life-threatening): Altered mental status, decreased testicular size, depression, disturbed sleep, hypersensitivity (angioedema, facial swelling, pharyngeal edema, pruritus, skin rash, swelling of the lips, swollen tongue, urticaria), male infertility (temporary), malignant neoplasm of the male breast, prostate cancer - high grade, prostatitis, reduction in penile curvature, reduction in penile size, sexual disorder (may not be reversible with discontinuation), testicular pain

Warnings/Precautions

Disease-related concerns:

• Diminished urinary flow: Carefully monitor patients with a large residual urinary volume or severely diminished urinary flow for obstructive uropathy; these patients may not be candidates for finasteride therapy.

• Hepatic impairment: Use with caution in patients with hepatic impairment; finasteride is extensively metabolized in the liver.

• Prostate cancer: When compared to placebo, 5-alpha-reductase inhibitors (5-ARIs) have been associated with an increase in the incidence of high-grade prostate cancers; 5-ARIs are not approved in the U.S. or Canada for the prevention of prostate cancer.

Special handling:

• Hazardous agent: Use appropriate precautions for handling and disposal (NIOSH 2014 [group 3]).

• Women/pregnancy: Active ingredient of crushed or broken tablets can be absorbed through the skin; unbroken tablets are coated which prevents contact with the active ingredient during normal handling. Women should avoid contact with crushed or broken tablets and the semen from a male partner exposed to finasteride; finasteride may negatively impact fetal development.

Other warnings/precautions:

• Appropriate use: Other urological diseases (including prostate cancer) should be ruled out before initiating.

• Duration of therapy: For BPH, a minimum of 6 months of treatment may be necessary to determine whether an individual will respond to finasteride; for male pattern hair loss, daily use for 3 months or longer may be required before benefit is observed (withdrawal of treatment leads to reversal of hair growth effect within 12 months).

• PSA monitoring: Reduces prostate specific antigen (PSA) concentration by ~50% within 6 months of treatment. To interpret serial PSAs, a new PSA baseline should be established ≥6 months after treatment initiation and PSA monitored periodically thereafter. A confirmed PSA increase while on this medication, even if within normal limits, may be associated with an increased risk for prostate cancer and should be evaluated. Finasteride does not interfere with free PSA levels.

Monitoring Parameters

To interpret serial PSAs, establish a new PSA baseline ≥6 months after treatment initiation and monitor PSA periodically thereafter. Objective and subjective signs of relief of benign prostatic hyperplasia, including improvement in urinary flow, reduction in symptoms of urgency, and relief of difficulty in micturition.

Pregnancy Risk Factor

X

Pregnancy Considerations

Abnormalities of external male genitalia were reported in animal reproduction studies. Use is not indicated in women. Pregnant women are advised to avoid contact with crushed or broken tablets and the semen from a male partner exposed to finasteride.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience sexual dysfunction or decreased libido. Have patient report immediately to prescriber lump in breast, mastalgia, or nipple discharge (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience and judgment in diagnosing, treating and advising patients.

Hide