Dutasteride

Pronunciation

Pronunciation: doo-TAS-ter-ide
Class: Androgen hormone inhibitor

Trade Names

Avodart
- Capsules 0.5 mg

Pharmacology

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

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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 half-life is approximately 5 wk.

Special Populations

Renal Function Impairment

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

Hepatic Function Impairment

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

Elderly

Dutasteride half-life increases with age; however, no dosage adjustment is necessary in elderly patients.

Children

Pharmacokinetics have not been investigated.

Gender

Pharmacokinetics have not been studied in women.

Race

Effect of race on dutasteride pharmacokinetics have not been studied.

Indications and Usage

As monotherapy or in combination with tamsulosin for the 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.

Unlabeled Uses

Prostate cancer prevention.

Contraindications

Pregnancy; women of childbearing potential; children; hypersensitivity to 5-alpha-reductase inhibitors or any component of the product.

Dosage and Administration

Adults

PO 0.5 mg once daily. May be given as monotherapy or in combination with tamsulosin 0.4 mg once daily.

General Advice

  • Administer with or without food.
  • Swallow capsules whole. Do not crush, cut, or chew.
  • Do not use capsules that are cracked or leaking.

Storage/Stability

Store at 59° to 86°F.

Drug Interactions

CYP3A4 inhibitors (eg, cimetidine, ciprofloxacin, diltiazem, ketoconazole, ritonavir, troleandomycin, verapamil)

Plasma concentrations of dutasteride may be elevated, increasing the risk of adverse reactions. Use with caution. However, the change in dutasteride exposure with coadministration of diltiazem or verapamil is not considered clinically important, and no dosage adjustment is recommended.

Food

When dutasteride is taken with food, the dutasteride C max is reduced 10% to 15%. This reduction is not considered to be clinically important. Dutasteride may be taken with or without food.

Laboratory Test Interactions

Decreased prostate-specific antigen (PSA) levels. The decrease is predictable over the entire range of PSA values, although it may vary in individual patients. Therefore, for interpretation of serial PSA values in a man taking dutasteride, establish a new baseline PSA concentration after 3 to 6 months of treatment. This new value should be used to assess potentially cancer-related PSA changes.

Adverse Reactions

CNS

Decreased libido (3%).

Genitourinary

Impotence (5%); breast disorder including breast enlargement and breast tenderness, ejaculation disorder (1%).

Hypersensitivity

Allergic reactions, including angioedema, localized edema, pruritus, rash, serious skin reactions, and 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

Contraindicated for use in 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. Dutasteride is absorbed through the skin and could result in unintended fetal exposure. 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.

Prostate effects

Total serum PSA concentrations are decreased. Establish a new baseline PSA concentration after 3 to 6 mo of treatment and use this new value to assess potentially cancer-related changes in PSA. To interpret an isolated PSA value in a man treated with dutasteride for 6 mo or more, double the PSA value for comparison with normal values in untreated men.

Reproductive effects

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 maximum benefit.
  • Advise patient to swallow the capsule whole and to not chew or open the capsule.
  • Advise patient that ejaculate volume may be decreased during treatment, but 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 decreased libido, impotence, 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.

Copyright © 2009 Wolters Kluwer Health.

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