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Pronunciation |
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(fi
NAS teer
ide) |
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U.S. Brand
Names |
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Proscar® |
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Generic
Available |
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No |
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Pharmacological Index |
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Antiandrogen |
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Use |
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Early data indicate that finasteride is useful in the treatment of
symptomatic benign prostatic hyperplasia (BPH); male pattern baldness
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Pregnancy Risk
Factor |
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X |
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Contraindications |
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History of hypersensitivity to drug, pregnancy, lactation,
children |
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Warnings/Precautions |
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A minimum of 6 months of treatment may be necessary to determine whether an
individual will respond to finasteride. Use with caution in those patients with
liver function abnormalities. 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. |
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Adverse
Reactions |
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1% to 10%:
Genitourinary: <4% incidence of impotence, decreased volume of ejaculate
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Drug
Interactions |
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CYP3A3/4 enzyme substrate |
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Mechanism of
Action |
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Finasteride is a 4-azo analog of testosterone and 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; depending on dose and duration, serum testosterone
concentrations may or may not increase. Testosterone-dependent processes such as
fertility, muscle strength, potency, and libido are not affected by
finasteride. |
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Pharmacodynamics/Kinetics |
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Onset of clinical effect: Within 12 weeks to 6 months of ongoing therapy
Duration of action:
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
Absorption: Oral: Extent may be reduced if administered with food
Metabolism: Unchanged finasteride is major circulating component; two active
metabolites have been identified
Protein binding: 90%
Bioavailability: Mean: 63%
Half-life, serum: Parent drug: ~5-17 hours (mean: 1.9 fasting, 4.2 with
breakfast)
Half-life: Elderly: 8 hours; Adults: 6 hours (3-16)
Time to peak serum concentration: Oral: 2-6 hours
Elimination: As metabolites in urine (39%) and feces (57%); elimination rate
is decreased in the elderly, but no dosage adjustment is needed
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Usual Dosage |
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Adults: Male:
Male pattern baldness: Oral: 1 mg daily
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 |
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Dietary
Considerations |
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Food: Administration with food may delay the rate and reduce the extent of
oral absorption |
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Monitoring
Parameters |
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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 |
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Mental Health: Effects
on Mental Status |
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None reported |
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Mental Health:
Effects on Psychiatric
Treatment |
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None reported |
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Dental Health: Local
Anesthetic/Vasoconstrictor
Precautions |
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No information available to require special precautions |
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Dental Health:
Effects on Dental Treatment |
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No effects or complications reported |
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Patient
Information |
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Results of therapy may take several months. Take as directed, with fluids, 30
minutes before or 2 hours after meals. You may experience decreased libido or
impotence during therapy. Report any increase in urinary volume or voiding
patterns occurs. Pregnancy precautions: This drug will cause fetal
abnormalities - use barrier contraceptives and do not allow childbearing age
women to touch or handle drug. |
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Nursing
Implications |
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Monitor 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 |
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Dosage Forms |
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Tablet, film coated: 1 mg, 5 mg |
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References |
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Jeffrey LP, Chairman, National Study Commission on Cytotoxic Exposure.
Position Statement.
"The Handling of Cytotoxic Agents by Women Who Are Pregnant, Attempting to Conceive, or Breast-Feeding,"
January 12, 1987.
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.
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