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Pronunciation
(fi NAS teer ide)
Generic Available (U.S.)
Yes
U.S. Brand Names
Canadian Brand Names
Pharmacologic Category
Use: Labeled Indications
Propecia®: Treatment of male pattern hair loss in men only. Safety and efficacy were demonstrated in men between 18-41 years of age.
Proscar®: Treatment of symptomatic benign prostatic hyperplasia (BPH); can be used in combination with an alpha-blocker, doxazosin
Use: Unlabeled/Investigational
Prostate cancer prevention (to reduce the incidence); treatment of female hirsutism
Pregnancy Risk Factor
X
Pregnancy Considerations
Abnormalities of external male genitalia were reported in animal studies. Pregnant women are advised to avoid contact with crushed or broken tablets.
Lactation
Excretion in breast milk unknown/contraindicated in women of childbearing potential
Breast-Feeding Considerations
Not indicated for use in women.
Contraindications
Hypersensitivity to finasteride or any component of the formulation; pregnancy; not for use in children
Warnings/Precautions
Special handling:
• Hazardous agent: Use appropriate precautions for handling and disposal.
• Women/pregnancy: Active ingredient can be absorbed through the skin; women should always use caution whenever handling. Pregnant women or women trying to conceive should not handle the product; finasteride may negatively impact fetal development.
Disease-related concerns:
• Breast changes: Patients should promptly report any breast changes, including lumps, pain, or nipple discharge.
• 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 have been shown to reduce the incidence of prostate cancer, although an increase in the incidence of high-grade prostate cancers has been observed (Kramer, 2009; Thompson, 2003).
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.
• PSA monitoring: Reduces prostate specific antigen (PSA) by 50%; in patients treated for ≥6 months the PSA should be doubled when comparing to normal ranges in untreated patients. Failure to demonstrate a meaningful PSA response (<50% decrease) or a PSA increase is associated with an increased risk for prostate cancer (NCCN prostate cancer early detection guidelines, v.2.2010). Patients with any increase in PSA levels should be evaluated; may indicate presence of prostate cancer.
Adverse Reactions
Note: “Combination therapy” refers to finasteride and doxazosin.
>10%:
Endocrine & metabolic: Impotence (5% to 19%; combination therapy 23%), libido decreased (2% to 10%; combination therapy 12%)
Neuromuscular & skeletal: Weakness (5%; combination therapy 17%)
1% to 10%:
Cardiovascular: Postural hypotension (9%; combination therapy 18%), edema (1%; combination therapy 3%)
Central nervous system: Dizziness (7%; combination therapy 23%), somnolence (2%; combination therapy 3%)
Dermatologic: Rash (1%)
Genitourinary: Ejaculation disturbances (<1% to 7%; combination therapy 14%), decreased volume of ejaculate (2% to 4%)
Endocrine & metabolic: Gynecomastia (1% to 2%), breast tenderness (≤1%)
Respiratory: Dyspnea (1%; combination therapy 2%), rhinitis (1%; combination therapy 2%)
<1%, postmarketing, and/or case reports: Breast cancer (males), depression, hypersensitivity (pruritus, rash, urticaria, swelling of face/lips), prostate cancer (high grade), testicular pain
Metabolism/Transport Effects
Substrate of CYP3A4 (minor)
Drug Interactions
Conivaptan: May increase the serum concentration of CYP3A4 Substrates. Management: Upon completion/discontinuation of conivaptan, allow at least 7 days before initiating therapy with drugs that are CYP3A4 substrates. Risk D: Consider therapy modification
Tocilizumab: May decrease the serum concentration of CYP3A4 Substrates. Risk C: Monitor therapy
Ethanol/Nutrition/Herb Interactions
Herb/Nutraceutical: St John's wort may decrease finasteride levels. Avoid saw palmetto (concurrent use has not been adequately studied).
Storage
Propecia®: Store at 15°C to 30°C (59°F to 86°F). Protect from moisture.
Proscar®: Store below 30°C (86°F). Protect from light.
Mechanism of Action
Finasteride is a competitive inhibitor of both tissue and hepatic 5-alpha reductase. This results in inhibition of the conversion of testosterone to dihydrotestosterone and markedly suppresses serum dihydrotestosterone levels
Pharmacodynamics/Kinetics
Onset of action: BPH: 6 months; Male pattern hair loss: ≥3 months of daily use
Duration:
After a single oral dose as small as 0.5 mg: 65% depression of plasma dihydrotestosterone levels persists 5-7 days
After 6 months of treatment with 5 mg/day: Circulating dihydrotestosterone levels are reduced to castrate levels without significant effects on circulating testosterone; levels return to normal within 14 days of discontinuation of treatment
Distribution: Vdss: 76 L
Protein binding: ~90%
Metabolism: Hepatic via CYP3A4; two active metabolites (<20% activity of finasteride)
Bioavailability: Mean: 65%
Half-life elimination, serum: 6 hours (range: 3-16 hours); Elderly: 8 hours (range: 6-15 hours)
Time to peak, serum: 1-2 hours
Excretion: Feces (57%) and urine (39%) as metabolites
Dosage
Oral: Adults:
Male:
Benign prostatic hyperplasia (Proscar®): 5 mg once daily as a single dose; clinical responses occur within 12 weeks to 6 months of initiation of therapy; long-term administration is recommended for maximal response
Male pattern baldness (Propecia®): 1 mg daily
Prostate cancer prevention (unlabeled use): 5 mg once daily; planned duration of treatment was 7 years (Kramer, 2009; Thompson, 2003)
Female hirsutism (unlabeled use): 5 mg/day (Moghetti, 2000)
Dosing adjustment in renal impairment: No dosage adjustment is necessary
Dosing adjustment in hepatic impairment: Use with caution in patients with liver function abnormalities because finasteride is metabolized extensively in the liver
Administration: Oral
May be administered without regard to meals. Women of childbearing age should not touch or handle broken tablets.
Monitoring Parameters
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
Dietary Considerations
May be taken without regard to meals.
Patient Education
Take with or without meals. May cause decreased libido or impotence during therapy. Report any changes in urinary pattern (significant increase or decrease in volume or voiding patterns). Report changes in breast condition (pain, lumps, or nipple discharge) in male and female patients.
Geriatric Considerations
Clearance of finasteride is decreased in the elderly, but no dosage reductions are necessary.
Anesthesia and Critical Care Concerns/Other Considerations
Finasteride may be useful in men with moderately symptomatic BPH who either refuse prostatectomy or are poor surgical candidates. Currently, there is no way to predict which men will respond to finasteride. Treatment with finasteride does not alter the ratio of free to total PSA, which is used to detect prostatic cancer.
Dental Health: Effects on Dental Treatment
No significant effects or complications reported
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
None reported
Mental Health: Effects on Psychiatric Treatment
None reported
Nursing: Physical Assessment/Monitoring
Assess urinary pattern prior to therapy and periodically during therapy. A minimum of 6 months of treatment may be necessary to evaluate response.
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, oral: 5 mg
Propecia®: 1 mg
Proscar®: 5 mg
Pricing: U.S. (www.drugstore.com)
Tablets (Propecia)
1 mg (90): $184.99
Tablets (Proscar)
5 mg (30): $112.99
References
Kramer BS, Hagerty KL, Justman S, et al, “Use of 5-α-Reductase Inhibitors for Prostate Cancer Chemoprevention: American Society of Clinical Oncology/American Urological Association 2008 Clinical Practice Guideline,” J Clin Oncol, 2009, 27(9):1502-16.
Lepor H, Williford WO, Barry MJ, et al, “The Efficacy of Terazosin, Finasteride, or Both in Benign Prostatic Hyperplasia,” N Engl J Med, 1996, 335(8):533-9.
McConnell JD, Roehrborn CG, Bautista OM, et al, “The Long-Term Effect of Doxazosin, Finasteride, and Combination Therapy on the Clinical Progression of Benign Prostatic Hyperplasia. Medical Therapy of Prostatic Symptoms (MTOPS) Research Group,” N Engl J Med, 2003, 349(25):2387-98.
Moghetti P, Tosi F, Tosti A, et al, “Comparison of Spironolactone, Flutamide, and Finasteride Efficacy in the Treatment of Hirsutism: A Randomized, Double Blind, Placebo-Controlled Trial,” J Clin Endocrinol Metab, 2000, 85(1):89-94.
National Comprehensive Cancer Network® (NCCN), “Clinical Practice Guidelines in Oncology™: Prostate Cancer Early Detection,” Version 2.2010. Available at http://www.nccn.org/professionals/physician_gls/PDF/prostate_detection.pdf
Pole M and Koren G, “Finasteride. Does It Affect Spermatogenesis and Pregnancy,” Can Fam Physician, 2001, 47:2469-70.
Thompson IM, Goodman PJ, Tangen CM, et al, “The Influence of Finasteride on the Development of Prostate Cancer,” N Engl J Med, 2003, Jul 349(3):215-24.
International Brand Names
Lexi-Comp.com
Last full review/revision May 2011
Content last modified May 2011
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