Tamsulosin
Tamsulosin is an **alpha-1 adrenergic antagonist** with high selectivity for the urinary tract. It works by relaxing the smooth muscle in the prostate, urethra, and bladder neck, thereby aiding urine flow. It has a longer duration of action compared to other alpha-blockers like prazosin or phenoxybenzamine. **Clinical Pearl:** In veterinary medicine, tamsulosin is frequently used off-label to manage functional urinary retention, benign prostatic hyperplasia (BPH) in intact male dogs, and to facilitate the medical expulsive therapy of ureteroliths or uroliths.
Mecanismo: Tamsulosin selectively binds to and blocks **alpha-1A and alpha-1D adrenergic receptors** located predominantly in the smooth muscle of the prostate, prostatic capsule, prostatic urethra, and bladder neck. Blockade of these receptors → relaxation of smooth muscle → decreased urethral resistance → improved urine flow and relief of functional urinary obstruction.
Vías de administración
Contraindicaciones
- Hypersensitivity to tamsulosin
- Severe hepatic impairment
- History of orthostatic hypotension
Efectos adversos
- Hypotension
- Lethargy
- Weakness
- Gastrointestinal upset (vomiting, diarrhea)
- Dizziness
Interacciones farmacológicas
- Other alpha-1 blockers (e.g., prazosin, phenoxybenzamine) · Additive hypotensive effects · major
- Calcium channel blockers (e.g., amlodipine) · Increased risk of hypotension · moderate
- Cimetidine · Decreased clearance of tamsulosin, potentially increasing plasma concentrations · minor
Monitorización
- Urine output and ease of urination
- Blood pressure
- Renal function
Sobredosis
Overdosage may lead to severe **hypotension**. Treatment is primarily supportive, including intravenous fluid therapy and potentially vasopressors if hypotension is refractory. Emesis or gastric lavage may be considered if ingestion is recent.
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