Classifications: alpha-adrenergic antagonist;
Therapeutic: smooth muscle relaxant of bladder outlet & prostate gland

Prototype: Prazosin HCl
Pregnancy Category: B


0.4 mg capsules


Antagonist of the alpha1A-adrenergic receptors located in the prostate. Blockage of alpha1A-adrenergic receptors can cause smooth muscles in the bladder outlet and the prostate gland to relax, resulting in improvement in urinary blood flow and a reduction in symptoms of BPH.

Therapeutic Effect

Effectiveness is indicated by improved voiding. Improves symptoms related to benign prostatic hypertrophy (BPH) related to bladder outlet obstruction.


Benign prostatic hypertrophy.


Hypersensitivity to tamsulosin; in conjunction with another alpha1A-adrenergic blocking agent; women; lactation, pediatric patients.

Cautious Use

History of syncope, hypersensitivity to sulfonamides; hypotension; older adults; renal impairment, renal failure, renal disease; pregnancy (category B).

Route & Dosage

Benign Prostatic Hypertrophy
Adult: PO 0.4 mg q.d. 30 min after a meal, may increase up to 0.8 mg q.d.


  • Give 30 min after the same meal each day.
  • Instruct to swallow capsules whole; not to crush, chew, or open.
  • If dose is interrupted for several days, reinitiate at the lowest dose, 0.4 mg.
  • Store at 20°–25° C (68°–77° F).

Adverse Effects (≥1%)

Body as a Whole: Asthenia, back or chest pain. CNS: Headache, dizziness, insomnia. CV: Orthostatic hypotension (especially with first dose). GI: Diarrhea, nausea. Respiratory: Rhinitis, pharyngitis, increased cough, sinusitis. Urogenital: Decreased libido, abnormal ejaculation. Special Senses: Amblyopia.


Drug: Cimetidine may decrease clearance of tamsulosin. Sildenafil, vardenafil, and tadalafil, and alcohol may enhance hypotensive effects.


Absorption: Rapidly from GI tract. >90% bioavailability. Peak: 4–5 h fasting, 6–7 h fed. Distribution: Widely distributed in body tissues, including kidney and prostate. Metabolism: In the liver. Elimination: 76% in urine. Half-Life: 14–15 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor for signs of orthostatic hypotension; take BP lying down, then upon standing. Report a systolic pressure drop of ≥15 mm Hg or a HR ≥15 beats upon standing.
  • Monitor patients on warfarin therapy closely.

Patient & Family Education

  • Make position changes slowly to minimize orthostatic hypotension.
  • Report dizziness, vertigo, or fainting to physician. Exercise caution with hazardous activities until response to drug is known.
  • Be aware that concurrent use of cimetidine may increase the orthostatic hypotension adverse effect.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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