## α1-Adrenergic Antagonists in BPH: Receptor Selectivity **Key Point:** Tamsulosin is a uroselective α1A-antagonist that preferentially blocks α1A receptors in the prostate and bladder neck while sparing α1B receptors in blood vessels, resulting in minimal vasodilation and hypotension. ### Receptor Subtype Distribution | Drug | α1A Selectivity | α1B Blockade | Cardiovascular Effects | BPH Efficacy | |------|-----------------|--------------|------------------------|---------------| | **Tamsulosin** | High (uroselective) | Minimal | Minimal | Excellent | | Prazosin | Non-selective | High | Significant hypotension | Good but side effects | | Doxazosin | Non-selective | High | Significant hypotension | Good but side effects | | Phentolamine | Non-selective | High | Severe hypotension | Not used for BPH | **High-Yield:** Tamsulosin's uroselective action on α1A receptors (abundant in prostate) versus α1B receptors (abundant in vascular smooth muscle) makes it the preferred first-line agent for BPH with concurrent hypertension, as it avoids orthostatic hypotension and syncope. ### Clinical Pharmacology 1. **Tamsulosin mechanism:** Selective antagonism of α1A-adrenergic receptors in prostatic and bladder neck smooth muscle → relaxation → improved urinary flow 2. **Minimal vascular effect:** Spares α1B receptors in arteries and veins → no significant blood pressure reduction 3. **Dosing:** 0.4–0.8 mg once daily (long-acting formulation) **Clinical Pearl:** Tamsulosin is absorbed better with food and should be taken 30 minutes after the same meal each day for consistent plasma levels. **Tip:** When a question emphasizes "selective" or "uroselective" antagonism in the context of BPH with hypertension, think tamsulosin — it is the only α1-blocker with clinically meaningful receptor selectivity.
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