finasteride
(fin as' teh ride)
Propecia, Proscar
Pregnancy Category X
Drug class
Androgen hormone inhibitor
Therapeutic actions
Inhibits the intracellular enzyme that converts testosterone into a potent androgen (DHT); does not affect androgen receptors in the body; the prostate gland depends on DHT for its development and maintenance.
Indications
· Proscar: Treatment of symptomatic BPH; most effective with long-term use; reduces the need for prostate surgery and reduces the risk of urinary retention; with doxazosin, to reduce the risk of progression of BPH symptoms
· Propecia: Prevention of male pattern baldness in patients with family history or early signs of loss
· Unlabeled uses: Adjuvant monotherapy following radical prostatectomy; prevention of the progression of first-stage prostate cancer; hirsutism; male chronic pelvic pain syndrome
Contraindications and cautions
· Contraindicated with allergy to finasteride or any component of the product, pregnancy, lactation.
· Use cautiously with hepatic impairment.
Available forms
Tablets—1 mg (Propecia), 5 mg (Proscar)
Dosages
ADULTS
· BPH: 5 mg daily PO with or without meals; may take 6–12 mo for response.
· Male pattern baldness: 1 mg/day PO.
PEDIATRIC PATIENTS
Safety and efficacy not established.
GERIATRIC PATIENTS OR PATIENTS WITH RENAL INSUFFICIENCY
No dosage adjustment is needed.
Pharmacokinetics
Route | Onset | Peak | Duration |
Oral | Rapid | 8 hr | 24 hr |
Metabolism: Hepatic; T1/2: 6 hr
Distribution: Crosses placenta; may enter breast milk (not used in women)
Excretion: Feces, urine
Adverse effects
· GI: Abdominal upset
· GU: Impotence, decreased libido, decreased volume of ejaculation
· Other: Gynecomastia
Interactions
Drug-lab test
· Decreased PSA levels when measured; false decrease does not mean patient is free of risk of prostate cancer
Nursing considerations
Assessment
· History: Allergy to finasteride or any component, hepatic impairment, pregnancy, lactation
· Physical: Liver evaluation, abdominal examination; renal function tests, normal urine output, prostate examination
Interventions
· Confirm that problem is BPH, and other disorders (prostate cancer, infection, strictures, hypotonic bladder) have been ruled out.
· Administer without regard to meals; protect container from light.
· Arrange for regular follow-up, including prostate examination, PSA levels, and evaluation of urine flow.
· Monitor urine flow and output; increase in urine flow may not occur in all situations.
· WARNING: Do not allow pregnant women to handle crushed or broken tablets because of risk of inadvertent absorption, adversely affecting the fetus.
· Alert patient that libido may be decreased as well as the volume of ejaculate; usually reversible when the drug is stopped.
Teaching points
· Take this drug once a day without regard to meals; protect from light.
· Have regular medical follow-up to evaluate your response. Your health care provider will monitor your liver and kidney function as well as prostate-specific antigen (PSA) levels.
· This drug has serious adverse effects on unborn babies. Do not allow a pregnant woman to handle the tablet if it is crushed or broken.
· You may experience these side effects: Loss of libido, impotence, decreased amount of ejaculate (usually reversible when the drug is stopped); breast enlargement, tenderness.
· Report inability to void, groin pain, sore throat, fever, weakness.
Adverse effects in Italic are most common; those in Bold are life-threatening.
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