Why is Flomax (tamsulosin) given to a male patient over 50 years old with benign prostatic hyperplasia (BPH)?

Why Flomax (Tamsulosin) is Given

Flomax (tamsulosin) is prescribed to relieve bothersome lower urinary tract symptoms (LUTS) in men with benign prostatic hyperplasia (BPH) by relaxing prostatic smooth muscle, thereby improving urinary flow and reducing obstructive symptoms. 1

Mechanism of Action

• Tamsulosin is an alpha-1A and alpha-1D adrenoceptor antagonist that selectively inhibits alpha-1-adrenergic-mediated contraction of prostatic smooth muscle, which relieves bladder outlet obstruction 2, 3
• The drug targets alpha-1 receptors that predominate in the prostate gland, prostatic capsule, prostatic urethra, and bladder, leading to smooth muscle relaxation 3
• Unlike 5-alpha-reductase inhibitors, tamsulosin does not reduce prostate size—it only addresses the dynamic component of obstruction 4

Clinical Efficacy

• Tamsulosin 0.4 mg once daily produces a 12% improvement in urinary symptom scores (mean reduction of 1.1 points on the Boyarsky scale) compared to placebo 5, 6
• Peak urine flow rate (Qmax) increases by approximately 1.1 mL/sec compared to placebo, with improvements evident as early as 1 week after starting treatment 1, 5
• The drug is effective in patients with mild to severe LUTS, in elderly patients, and in those with diabetes mellitus 3
• Efficacy is maintained for up to 6 years based on pooled long-term data 3

Appropriate Patient Selection

• The standard patient is a man older than 50 years presenting with bothersome moderate-to-severe LUTS that may or may not be associated with an enlarged prostate 7
• Tamsulosin is appropriate for men with voiding symptoms (hesitancy, weak stream, incomplete emptying, intermittency) rather than predominantly storage symptoms (urgency, frequency) 7, 8
• The American Urological Association recommends alpha-blockers like tamsulosin for men with bothersome moderate-to-severe LUTS from BPH 8

Dosing and Administration

• The standard dosage is 0.4 mg once daily in a modified-release formulation, taken approximately 30 minutes after the same meal each day 4, 1
• No initial dose titration is required, which is an advantage over non-selective alpha-blockers 4, 3
• Capsules should not be crushed, chewed, or opened 1

Important Clinical Considerations and Pitfalls

• Intraoperative Floppy Iris Syndrome (IFIS): All patients planning cataract or glaucoma surgery must inform their ophthalmologist about tamsulosin use, as it causes IFIS and can complicate the procedure 8, 4, 1
• Orthostatic Hypotension: Tamsulosin can cause sudden drops in blood pressure upon standing, especially after the first dose—patients should change positions slowly and sit or lie down if dizziness occurs 1
• Ejaculatory Dysfunction: Tamsulosin has a higher risk of abnormal ejaculation compared to other alpha-blockers 4, 5
• Do Not Use Without a Prostate: Tamsulosin is completely ineffective in patients who have undergone prostatectomy, as the therapeutic target (prostatic smooth muscle) is absent 2
• Not for Prostate Size Reduction: Do not prescribe tamsulosin to reduce prostate volume—it does not affect prostate size and should not be used for this indication 4

Follow-up and Treatment Response

• For alpha-blockers like tamsulosin, the first follow-up should occur at 4 weeks to assess symptom improvement 8
• The first dose of tamsulosin can predict mid-term effectiveness: positive predictive value of 90.9% for third-month response based on initial uroflowmetry changes 9
• If patients stop or forget tamsulosin for several days, they should talk with their doctor before restarting 1

Alternative Considerations

• For patients with predominantly storage symptoms (urgency, frequency, nocturia), beta-3 agonists or anticholinergics targeting bladder overactivity are more appropriate than tamsulosin 8, 2
• For patients with significantly enlarged prostates, combination therapy with a 5-alpha-reductase inhibitor (finasteride or dutasteride) should be considered for long-term management 4
• Other alpha-blockers (alfuzosin, doxazosin, silodosin, terazosin) are equally effective alternatives with different side effect profiles 8

Common Adverse Effects

• Most frequent adverse events significantly greater than placebo include dizziness, rhinitis, and abnormal ejaculation 5, 6
• Rare but serious reactions include allergic reactions (rash, itching, hives, swelling of face/tongue/throat, difficulty breathing) and priapism (painful erection requiring immediate medical attention) 1
• Low-dose tamsulosin (0.2-0.4 mg) is generally well tolerated, but adverse effects increase markedly at higher doses (0.8 mg reported in 75% of patients) 5, 6