Dutasteride

INTRODUCTION

Indications

Management of the symptoms of 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 Effects: Reduced prostate size with associated decrease in urinary symptoms.

Adverse Reactions/Side Effects

GU: decreased libido, ejaculation disorders, erectile dysfunction. Endo: gynecomastia. Derm: rash, urticaria. Misc: ALLERGIC REACTIONS, ANGIOEDEMA.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Monitor signs of allergic reactions and angioedema, including pulmonary symptoms (tightness in the throat and chest, wheezing, cough, dyspnea), skin reactions (rash, pruritus, urticaria, swelling in the face). Notify physician immediately of these signs.

• Monitor signs of BPH such as difficulty starting a urine stream, painful urination, weak urine flow, feeling that the bladder is not completely empty, frequent nighttime urination, and an urge to urinate again soon after urinating. Document any change in BPH symptoms to help assess the effects of drug therapy.

Patient/Client-Related Instruction

• When treating BPH, advise patient that urinary symptoms (retention, dribbling, hesitancy, urgency) should improve, and to contact the physician if these symptoms continue to worsen.

• Instruct patient or family/caregivers to report other bothersome side effects such as breast enlargement (gynecomastia), severe or prolonged skin reactions (rash, hives), or sexual dysfunction (decreased libido, ejaculation disorders, erectile dysfunction).

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.

Contraindications/Precautions

Contraindicated in: Hypersensitivity; Cross-sensitivity with other 5-alpha-reductase inhibitors may occur; Women; Pedi: Children.

Use Cautiously in: Hepatic impairment.

Interactions

Drug-Drug: Blood levels and effects may be increased 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.