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Tamsulosin

Tamsulosin hydrochloride

Flomax Urimax Tamsin Contiflo Tamlet

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Updated: December 06, 2025

Overview

Tamsulosin is a selective alpha-1A adrenergic receptor antagonist primarily used for the treatment of benign prostatic hyperplasia (BPH). It works by relaxing smooth muscles in the prostate and bladder neck, improving urine flow and reducing urinary retention. The drug is pharmacologically distinct from non-selective alpha-blockers due to its preferential targeting of alpha-1A receptors in the genitourinary tract. Tamsulosin is generally well-tolerated but may cause dizziness, orthostatic hypotension, and retrograde ejaculation. It has a favorable pharmacokinetic profile allowing once-daily dosing and shows minimal effects on blood pressure compared to non-selective alpha-blockers. Clinical effects are typically noticed within 2-4 weeks of initiation.

Drug Class

Selective alpha-1 adrenergic blocker (specifically alpha-1A subtype) Therapeutic category: Genitourinary smooth muscle relaxant

Mechanism of Action

Competitively blocks postsynaptic alpha-1 adrenergic receptors (primarily alpha-1A subtype) in: • Prostate smooth muscle • Bladder neck • Prostatic urethra This inhibition prevents norepinephrine-induced smooth muscle contraction, reducing dynamic component of bladder outlet obstruction.

Pharmacokinetics

Absorption: ~90% oral bioavailability • Food decreases absorption by ~30% • High-fat meals significantly affect absorption Distribution: • Extensively distributed (Vd: 0.2-0.3 L/kg) • >90% plasma protein bound Metabolism: • Hepatic via CYP3A4 and CYP2D6 • Forms inactive metabolites Excretion: • Urine (76% as metabolites) • Feces (21%) Half-life: 9-13 hours in healthy adults

Pharmacodynamics

Primary effects: • Reduces urethral resistance • Increases urinary flow rate • Decreases residual urine volume Secondary effects: • Minimal impact on blood pressure • Reduced symptoms of bladder outlet obstruction

Indications

• Treatment of signs/symptoms of benign prostatic hyperplasia (BPH) • Management of lower urinary tract symptoms (LUTS) secondary to BPH • Off-label: Facilitate ureteral stone passage (distal ureteral stones <10mm)

Contraindications

Absolute: • Hypersensitivity to tamsulosin or components • Severe hepatic impairment (Child-Pugh C) Relative: • History of orthostatic hypotension • Concurrent use with strong CYP3A4 inhibitors • Patients undergoing cataract surgery (risk of IFIS)

Dosage & Administration

Benign Prostatic Hyperplasia: • Initial dose: 0.4 mg orally once daily • May increase to 0.8 mg once daily after 2-4 weeks • Administer 30 minutes after same meal each day Ureteral Stones (off-label): • 0.4 mg orally once daily until stone passage • Typically used for 4 weeks maximum

Special Populations

Pediatric: Not recommended (safety/efficacy not established) Geriatric: No dose adjustment required Renal impairment: No dose adjustment needed for mild-moderate impairment Hepatic impairment: Use caution in moderate impairment (Child-Pugh B); contraindicated in severe impairment

Adverse Effects

Common (>10%): • Dizziness (15-19%) • Abnormal ejaculation (8-18%) • Rhinitis (13%) • Headache (11%) Serious (<1%): • Priapism • Severe hypotension • Intraoperative Floppy Iris Syndrome (IFIS) • Syncope

Drug Interactions

• Other alpha-blockers: Enhanced hypotensive effects • CYP3A4 inhibitors (e.g., ketoconazole): Increased tamsulosin levels • PDE5 inhibitors (e.g., sildenafil): Additive hypotensive effects • Warfarin: Possible increased bleeding risk (theoretical) • Antihypertensives: Potentiated blood pressure lowering

Warnings & Precautions

• Orthostatic hypotension/syncope risk (especially first dose) • Screen for prostate cancer before treatment • Discontinue if angina pectoris worsens • Caution in patients with sulfa allergy (cross-reactivity possible) • Warn patients about potential intraoperative floppy iris syndrome (IFIS) during cataract surgery

Pregnancy & Lactation

Pregnancy: Category B (not indicated for use in women) Lactation: Not recommended (unknown if excreted in human milk)

Monitoring Parameters

• Blood pressure (especially initial weeks) • Urinary symptoms (IPSS score) • Prostate-specific antigen (PSA) if indicated • Liver function tests in hepatic impairment • Post-void residual volume if urinary retention suspected

Patient Counseling

• Take daily after same meal to optimize absorption • Rise slowly from sitting/lying position • Report dizziness, fainting, or prolonged/painful erections • Inform all healthcare providers about tamsulosin use before surgeries • Don't crush or chew capsules • Improvement may take 2-4 weeks

Storage & Stability

• Store at 20-25°C (68-77°F) • Protect from light and moisture • Keep in original container • Stable for 3 years from manufacture date

Clinical Pearls

• Therapeutic effect typically begins within 1-2 weeks • No dose adjustment needed in elderly • Less likely than non-selective alpha-blockers to cause hypotension • Discontinue at least 1 day prior to cataract surgery • Consider starting at lower dose if patient is sensitive to hypotensive effects

References

• UpToDate: Tamsulosin drug information • Micromedex: Tamsulosin hydrochloride monograph • Flomax® (tamsulosin hydrochloride) FDA prescribing information • AUA Guideline: Management of Benign Prostatic Hyperplasia (2021) • European Association of Urology Guidelines on Male LUTS (2023)