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Medication Safety Issues
Sound-alike/look-alike issues:
Proscar® may be confused with ProSom®, Prozac®, Psorcon®
Pronunciation
(fi NAS teer ide)
U.S. Brand Names
Generic Available
Yes
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
Adjuvant monotherapy after radical prostatectomy in the treatment of prostatic cancer; 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
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: Women can absorb the active ingredient through the skin and 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:
• 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.
Special populations:
• Pediatrics: Safety and efficacy have not been established in children.
Other warnings/precautions:
• Appropriate use: Other urological diseases including cancer should be ruled out before initiating.
• Duration of therapy: A minimum of 6 months of treatment may be necessary to determine whether an individual will respond to finasteride.
• 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.
Adverse Reactions
Note: “Combination therapy” refers to finasteride and doxazosin.
>10%:
Endocrine & metabolic: Impotence (19%; combination therapy 23%), libido decreased (10%; combination therapy 12%)
Genitourinary: 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%)
Genitourinary: Ejaculation disturbances (7%; combination therapy 14%), decreased volume of ejaculate
Endocrine & metabolic: Gynecomastia (2%)
Respiratory: Dyspnea (1%; combination therapy 2%), rhinitis (1%; combination therapy 2%)
<1%, postmarketing, and/or case reports: Hypersensitivity (pruritus, rash, urticaria, swelling of face/lips); breast tenderness, breast enlargement, breast cancer (males), prostate cancer (high grade), testicular pain
Metabolism/Transport Effects
Substrate of CYP3A4 (minor)
Drug Interactions
There are no known significant interactions.
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
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: 3-6 months of ongoing therapy
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: 63%
Half-life elimination, serum: Elderly: 8 hours; Adults: 6 hours (3-16)
Time to peak, serum: 2-6 hours
Excretion: Feces (57%) and urine (39%) as metabolites
Dosage
Oral: Adults:
Male:
Benign prostatic hyperplasia (Proscar®): 5 mg/day 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
Female hirsutism (unlabeled use): 5 mg/day
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
Administration with food may delay the rate and reduce the extent of oral absorption. 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
Patient Education
Do not take any new medication during therapy unless approved by prescriber. Results of therapy may take several months. 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. Pregnancy precautions: This drug will cause fetal abnormalities - use barrier contraceptives and do not allow women of childbearing age to touch or handle broken or crushed tablets.
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 potential for interactions with pharmacological agents or herbal products patient may be taking. Assess urinary pattern prior to therapy and periodically during therapy (obstructive uropathy). Assess therapeutic effectiveness and signs/symptoms of adverse reactions. Teach patient proper use (eg, a minimum of 6 months of treatment may be necessary to evaluate response), possible side effects/appropriate interventions, and adverse symptoms to report. Pregnancy risk factor X - instruct patient on absolute need for barrier contraceptives. Women of childbearing age should not touch or handle broken tablets.
Oncology: Emetic Potential
Very low (<10%)
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet: 5 mg
Propecia®: 1 mg
Proscar®: 5 mg
Pricing: U.S. (www.drugstore.com)
Tablets (Proscar)
5 mg (30): $95.99
References
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.
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 August 2008
Content last modified August 2008
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