Overview
Dutasteride is a 5-alpha-reductase inhibitor used primarily for the treatment of symptomatic benign prostatic hyperplasia (BPH). It works by inhibiting the conversion of testosterone to dihydrotestosterone (DHT), reducing prostate size and improving urinary symptoms. The combination product with tamsulosin provides both symptom relief and disease progression modification.
Mechanism of Action
Dutasteride is a dual 5-alpha-reductase inhibitor that blocks both type 1 and type 2 isoenzymes, preventing the conversion of testosterone to dihydrotestosterone (DHT). This reduces DHT levels by approximately 90% within 2 weeks, leading to decreased prostate volume and improved urinary flow in BPH.
Indications
- Treatment of symptomatic benign prostatic hyperplasia (BPH) to improve symptoms, reduce risk of acute urinary retention, and reduce need for BPH-related surgery
- Reduction in risk of prostate cancer in men at increased risk (as part of combination therapy)
Common Doses
- 0.5 mg dutasteride (as monotherapy)
- 0.5 mg dutasteride/0.4 mg tamsulosin hydrochloride (combination product)
Dosage
The recommended dosage is 1 capsule (0.5 mg dutasteride and 0.4 mg tamsulosin hydrochloride) taken once daily approximately 30 minutes after the same meal each day. Capsules should be swallowed whole and not chewed or opened to avoid oropharyngeal mucosal irritation.
Contraindications
- Pregnancy (dutasteride may cause fetal harm to male fetus)
- Hypersensitivity to dutasteride, other 5-alpha-reductase inhibitors, tamsulosin, or any component of the formulation
- History of serious skin reactions, angioedema, urticaria, pruritus, or respiratory symptoms related to these components
Side Effects
- Erectile dysfunction
- Decreased libido
- Ejaculation disorders
- Gynecomastia
- Dizziness
- Orthostatic hypotension
- Headache
- Fatigue
Interactions
- Alpha-adrenergic antagonists: Increased risk of hypotension
- CYP3A4 inhibitors: May increase tamsulosin concentrations
- Phosphodiesterase-5 inhibitors: Potential additive hypotensive effects
- Warfarin: Monitor INR as dutasteride may affect metabolism
Counseling Points
- Take capsule whole, do not chew or open
- Take approximately 30 minutes after same meal daily
- May take several months to see full symptom improvement
- Report any dizziness, especially when standing up
- Do not donate blood while taking and for 6 months after stopping
- Inform all healthcare providers about this medication
- Use reliable contraception if partner could become pregnant