What is the indication for Duodart (dutasteride and tamsulosin)?

Duodart Indication

Duodart (dutasteride 0.5 mg plus tamsulosin 0.4 mg) is indicated for the treatment of moderate-to-severe lower urinary tract symptoms in men with benign prostatic hyperplasia (BPH) and demonstrable prostatic enlargement. 1

Primary Indications

Monotherapy Context (Dutasteride Component)

• Dutasteride is FDA-approved to improve symptoms, reduce the risk of acute urinary retention (AUR), and reduce the risk of BPH-related surgery in men with symptomatic BPH and an enlarged prostate 1

Combination Therapy (Duodart)

• The combination of dutasteride plus tamsulosin is specifically indicated for symptomatic BPH in men with an enlarged prostate, providing superior outcomes compared to either medication alone 1
• The American Urological Association strongly recommends this combination for patients with lower urinary tract symptoms (LUTS) associated with demonstrable prostatic enlargement, defined as prostate volume >30cc on imaging, PSA >1.5 ng/mL, or palpable prostate enlargement on digital rectal examination 2, 3

Patient Selection Criteria

Duodart is most appropriate for men meeting ALL of the following criteria:

• Age ≥50 years 4
• Moderate-to-severe LUTS (International Prostate Symptom Score/IPSS >8 or ≥12) 2, 3, 4
• Demonstrable prostatic enlargement (prostate volume >30 cm³) 2, 3, 4
• PSA level 1.5-10 ng/mL 4
• Maximum urinary flow rate (Qmax) >5 and ≤15 mL/s with minimum voided volume ≥125 mL 4

Patients with larger prostates (≥40 mL) and higher PSA values derive the greatest absolute benefit due to higher baseline risk of disease progression 2

Clinical Efficacy Evidence

• Combination therapy reduces overall BPH clinical progression by 67% compared to alpha-blocker monotherapy and provides superior symptom control over 4 years 2, 5
• The risk of acute urinary retention is reduced by 79% and the need for BPH-related surgery by 67% with combination therapy versus tamsulosin alone 2
• Symptom improvement (measured by IPSS) is significantly greater with combination therapy than either dutasteride or tamsulosin monotherapy, with benefits sustained over 4 years 6, 5
• Both storage and voiding symptoms improve more with combination therapy than with either monotherapy, with significant differences evident from 3 months onward 7

Mechanism of Action

• Dutasteride inhibits both type 1 and type 2 5-alpha-reductase enzymes, reducing serum DHT levels by approximately 95%, leading to 15-25% prostate volume reduction after 6 months 2
• Tamsulosin blocks alpha-1-adrenergic receptors in prostatic smooth muscle, providing relatively rapid symptom relief within weeks 3
• The combination targets different pathophysiologic mechanisms: dutasteride provides disease modification and long-term progression prevention, while tamsulosin provides immediate symptomatic relief 3, 6

Critical Limitations and Contraindications

• Duodart is NOT approved for the prevention of prostate cancer 1
• Absolutely contraindicated in pregnancy due to risk of fetal harm (inhibition of male fetal external genitalia development) 1
• Contraindicated in patients with previously demonstrated clinically significant hypersensitivity to dutasteride, tamsulosin, or other 5-alpha-reductase inhibitors 1
• Do NOT prescribe in men without demonstrable prostatic enlargement, as the 5-alpha-reductase inhibitor component is ineffective and exposes patients to unnecessary adverse effects 2, 3

Important Clinical Considerations

PSA Monitoring

• Dutasteride reduces serum PSA by approximately 50% within 3-6 months of treatment 1
• Establish a new PSA baseline at least 3 months after starting treatment; for interpretation of isolated PSA values after 3+ months of therapy, double the measured PSA value for comparison with normal ranges 2, 1
• Any confirmed increase from the lowest PSA value while on dutasteride may signal prostate cancer and requires evaluation, even if PSA remains within normal range 1

Onset of Action

• Tamsulosin provides relatively rapid symptom relief (weeks), while dutasteride has slower onset with typical improvement noticed after 3-6 months 2, 3
• Maximum prostate volume reduction and symptom benefit may take 6-12 months 2

Surgical Considerations

• Tamsulosin is associated with intraoperative floppy iris syndrome during cataract surgery; patients must inform ophthalmologists before any eye surgery 2, 3

Adverse Effects

• Sexual dysfunction occurs in 4-15% (erectile dysfunction), 6.4% (decreased libido in first year), and 3.7% (ejaculatory dysfunction in first year) 2
• Combination therapy adverse effects are consistent with the individual monotherapies, though drug-related adverse events are more frequent than placebo 8, 5
• Orthostatic hypotension risk from tamsulosin component 9

Dosing

• Dutasteride 0.5 mg plus tamsulosin 0.4 mg taken once daily 1
• Capsules must be swallowed whole and not chewed or opened, as contact with capsule contents may cause oropharyngeal mucosa irritation 1
• May be administered with or without food 1