dutasteride

General

Pronunciation
doo-TAS-te-ride [Pronunciation]

Trade Name(s)

• Avodart

Pregnancy Category
Category X

Ther. class.
benign prostatic hyperplasia bph agents

Pharm. class.
androgen inhibitors

Indications

Management of the symptoms of benign prostatic hyperplasia (BPH) in men with an enlarged prostate gland (alone or with tamsulosin).

Action

Inhibits the enzyme 5-alpha-reductase, which is responsible for converting testosterone to its potent metabolite 5-alpha-dihydrotestosterone in the prostate gland and other tissues. 5-Alpha-dihydrotestosterone is partly responsible for prostatic hyperplasia.

Therapeutic Effect(s):
Reduced prostate size with associated decrease in urinary symptoms.

Pharmacokinetics

Absorption: Well absorbed (60%) following oral administration; also absorbed through skin.

Distribution: 11.5% of serum concentration partitions into semen.

Protein Binding: 99% bound to albumin; 96.6% bound to alpha-1 glycoprotein.

Metabolism and Excretion: Mostly metabolized by the liver via the CYP3A4 metabolic pathway; metabolites are excreted in feces.

Half-life: 5 wk.

TIME/ACTION PROFILE (reduction in dihydrotestosterone levels†)

ROUTE	ONSET	PEAK	DURATION
PO	unknown	1-2 wk	unknown

†Symptoms may only improve over 3–12 mo

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity;

• Cross-sensitivity with other 5-alpha-reductase inhibitors may occur;

• Women;

• Pedi: Children.

Use Cautiously in:
Hepatic impairment.

Adverse Reactions/Side Effects

GU: PROSTATE CANCER (HIGH-GRADE) , ↓ libido, ejaculation disorders, erectile dysfunction.

Endo: gynecomastia.

Derm: rash, urticaria.

Misc: ALLERGIC REACTIONS, ANGIOEDEMA.

*CAPITALS indicates life-threatening.
*italic indicates most frequent.

Interactions

Drug-Drug
Blood levels and effects may be ↑ by ritonavir , ketoconazole , verapamil , diltiazem , cimetidine , ciprofloxacin , or other CYP3A4 enzyme inhibitors .

Route/Dosage

• PO (Adults): 0.5 mg once daily (with or without tamsulosin)..

Availability

• Soft gelatin capsules: 0.5 mg

• In combination with: tamsulosin (Jalyn); see combination drugs.

Assessment

• Assess patient for symptoms of prostatic hyperplasia (urinary hesitancy, feeling of incomplete bladder emptying, interruption of urinary stream, impairment of size and force of urinary stream, terminal urinary dribbling, straining to start flow, dysuria, urgency) before and periodically during therapy.

• Digital rectal examinations should be performed before and periodically during therapy for BPH.

Lab Test Considerations

• Serum prostate-specific antigen (PSA) concentrations, used to screen for prostate cancer, decrease by about 20% within the 1st mo of therapy and stabilize at about 50% of the pretreatment level within 6 mo. New baseline PSA concentrations should be established at 3 and 6 mo of therapy and evaluated periodically during therapy. Any increase in PSA during dutaseride therapy may be a sign of prostate cancer and should be evaluated, even those within normal limits. Isolated PSA values from men taking dutaseride for 3 mo or more should be doubled for comparison in untreated men.

Potential Nursing Diagnoses

• Impaired urinary elimination (Indications)

Implementation

PO: Administer once daily with or without meals. Do not break, crush, or chew capsule.

Patient/Family Teaching

• Instruct patient to take dutasteride at the same time each day as directed, even if symptoms improve or are unchanged. Take missed doses as soon as remembered later in the day or omit dose. Do not make up by taking double doses the next day.

• Caution patient that sharing of dutasteride may be dangerous.

• Inform patient that the volume of ejaculate may be decreased during therapy but that this will not interfere with normal sexual function.

• Advise patient to avoid donating blood for at least 6 mo after last dose of dutasteride to prevent a pregnant female from receiving dutasteride through a blood transfusion.

• Inform patient of potential increase risk in high-grade prostate cancer.

• Caution patient that dutasteride poses a potential risk to a male fetus. Women who are pregnant or may become pregnant should avoid exposure to semen of a partner taking dutasteride and should not handle dutasteride because of the potential for absorption.

• Emphasize the importance of periodic follow-up exams to determine whether a clinical response has occurred.

Evaluation/Desired Outcomes

Decrease in urinary symptoms of BPH.