Dutasteride

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

Absorption: Tmax is 2 to 3 hr; bioavailability is approximately 60%; administration with food decreased Cmax 10% to 15%.

Distribution: Vd is 300 to 500 L; highly protein bound.

Metabolism: Metabolized by CYP3A4.

Elimination: Mainly excreted in feces (approximately 5% as unchanged dutasteride and approximately 40% as metabolites). The t½ is approximately 5 wk.

 Indications Treatment of symptomatic benign prostatic hyperplasia in men with an enlarged prostate.

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

 Route/Dosage

Adults: PO 0.5 mg once daily.

 Interactions

Cytochrome P450 3A4 inhibitors (eg, cimetidine, ciprofloxacin, diltiazem, ketoconazole, ritonavir, verapamil): Plasma concentrations of dutasteride may be elevated, increasing the risk of side effects.

 Lab Test Interferences Decreased prostate-specific antigen levels.

 Adverse Reactions

GU: Impotence; decreased libido; ejaculation disorder; gynecomastia.

 Precautions

Pregnancy: Category X. Lactation: Undetermined. Children: Safety and efficacy not established. Hepatic impairment: Use with caution. Obstructive uropathy: Carefully monitor patients with large residual urine volume or severely diminished urinary flow.

 Administration/Storage

• Not for use in women.
• Do not handle dutasteride capsules if pregnant or possibly pregnant.
• Women who are not pregnant should use caution whenever handling dutasteride capsules. If contact is made with leaking capsules, wash the contacted area immediately with soap and water.
• Administer as prescribed once daily without regard to meals.
• Swallow capsules whole. Do not crush, cut, or chew.
• Do not use capsules that are cracked or leaking.
• Store at controlled room temperature (59° to 86°F). Protect from light.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies. Note history of liver disease.
• Ensure that patient has had complete physical examination to rule out causes of urinary tract symptoms other than BPH.
• Ensure that baseline PSA level is determined before starting therapy and periodically thereafter during therapy.
• Monitor urine volume and frequency for evidence of improvement in symptoms.

 Patient/Family Education

• Explain name, dose, action, and potential side effects of drug.
• 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 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.
• Instruct patient to not take any prescription or OTC medications or dietary supplements unless advised by health care provider.
• Advise patient that follow-up visits and lab tests will be required to monitor therapy and to keep appointments.