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Dutasteride

Pronunciation: (doo-TAS-teride)
Class: Androgen hormone inhibitor

Trade Names:
Avodart
- Capsules 0.5 mg

Pharmacology

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Inhibits the conversion of testosterone to 5-alpha-dihydrotestosterone, a potent androgen.

Pharmacokinetics

Absorption

T _max is 2 to 3 h; bioavailability is approximately 60%; administration with food decreased C _max 10% to 15%.

Distribution

Vd is 300 to 500 L; highly protein bound (99%).

Metabolism

Metabolized by CYP3A4 and CYP3A5.

Elimination

Mainly excreted in feces (approximately 5% as unchanged dutasteride and approximately 40% as metabolites). The t _½ is approximately 5 wk.

Special Populations

Renal Function Impairment

Pharmacokinetics have not been studied; however, no dosage adjustment is anticipated for patients with renal function impairment.

Hepatic Function Impairment

Pharmacokinetics have not been studied; however, because dutasteride is extensively metabolized, exposure could be higher in patients with hepatic function impairment.

Indications and Usage

Treatment of symptomatic benign prostatic hyperplasia (BPH) in men with enlarged prostate to improve symptoms, reduce the risk of acute urinary retention, and reduce the risk of need for BPH-related surgery.

Contraindications

Women; children; hypersensitivity to 5-alpha-reductase inhibitors or any component of the product.

Dosage and Administration

Adults

PO 0.5 mg once daily.

General Advice

Swallow capsules whole. Do not crush, cut, or chew.
Do not use capsules that are cracked or leaking.

Storage/Stability

Store at controlled room temperature (59° to 86°F).

Drug Interactions

CYP-450 3A4 inhibitors (eg, cimetidine, ciprofloxacin, diltiazem, ketoconazole, ritonavir, troleandomycin, verapamil)

Plasma concentrations of dutasteride may be elevated, increasing the risk of adverse reactions.

Laboratory Test Interactions

Decreased prostate-specific antigen levels.

Adverse Reactions

CNS

Decreased libido (3%).

Genitourinary

Impotence (5%); ejaculation disorder, gynecomastia (1%).

Hypersensitivity

Allergic reactions including angioedema, localized edema, pruritus, rash, urticaria (postmarketing).

Precautions

Monitor

Perform digital rectal exams, as well as other evaluations for prostate cancer prior to starting therapy and periodically thereafter. Assess patient to rule out other urologic diseases prior to treatment. Carefully monitor patients with large residual urine volume or severely diminished urinary flow for obstructive uropathy.

Pregnancy

Category X .

Lactation

Undetermined.

Children

Safety and efficacy not established.

Hepatic Function

Use with caution.

Blood donation

Men should not donate blood until at least 6 mo after the last dose of dutasteride.

Handling capsules

Women who are pregnant or may be pregnant should not handle the capsules. Women who are not pregnant should use caution whenever handling the capsules. If contact is made with leaking capsules, wash the contacted area immediately with soap and water.

Obstructive uropathy

Patients with large residual urine volume or severely diminished urinary flow may not be good candidates for therapy.

Reproductive function

Sperm count may be reduced in some patients.

Overdosage

Symptoms

Single doses of dutasteride 40 mg for 7 days have not produced safety concerns.

Patient Information

Advise patient to read the patient information leaflet before starting dutasteride and with each refill.
Advise patient that prescribed dose is to be taken once daily without regard to meals, and to try to take the dose at about the same time each day.
Advise patient that if a dose is missed to take as soon as remembered but to never take 2 doses the same day.
Advise patient that drug does not work immediately and that it may take 3 to 6 mo to experience max benefit.
Advise patient to swallow the capsule whole and do not chew or open the capsule.
Advise patient that ejaculate volume may be decreased during treatment but that this decrease does not interfere with normal sexual function.
Instruct patient to not stop taking dutasteride when symptoms have improved.
Caution patient that women who are or may be pregnant should not handle the medication because of risk of absorption though the skin and risk to developing male fetus.
Caution patient that a woman who is not pregnant can handle the capsules with caution, but if contact is made with a leaking capsule to wash the contacted area immediately with soap and water.
Advise patient that impotence, decreased libido, and ejaculation disorder may occur with therapy, but that these symptoms should lessen as treatment continues.
Advise patient against donating blood for at least 6 mo following discontinuation of therapy to prevent pregnant women from receiving dutasteride through a blood transfusion.