α-Blockers Nonselective α-Blockers Clinical Applications Toxicity Phenoxybenzamine (irreversible, preferred) Pheochromocytoma High catecholamine states Orthostatic hypotension Reflex tachycardia Phentolamine (reversible) Pheochromocytoma High catecholamine states Orthostatic hypotension Reflex tachycardia Selective α1-blockers (-zosin) Drug Clinical Applications Toxicity Prazosin Hypertension Urinary retention in benign prostatic hyperplasia (tamulosin is the most specific for urinary symptoms) First dose orthostatic hypotension Headache and dizziness Doxazosin Hypertension Urinary retention in benign prostatic hyperplasia (tamulosin is the most specific for urinary symptoms) First dose orthostatic hypotension Headache and dizziness Terazosin Hypertension Urinary retention in benign prostatic hyperplasia (tamulosin is the most specific for urinary symptoms) First dose orthostatic hypotension Headache and dizziness Tamulosin Hypertension Urinary retention in benign prostatic hyperplasia (tamulosin is the most specific for urinary symptoms) First dose orthostatic hypotension Headache and dizziness Selective α2 blockers Drug Clinical Applications Toxicity Mirtazapine Depression Sedation Xerostomia ↑ serum cholesterol ↑ appetite Yohimbine Male erectile dysfunction Hypotension Anxiety α-Blockers + Sympathomimetics effects Epi + α-blocker before non selective α-blocker is given, epi's net effect is to increase heart rate, contractility, and vasoconstriction leading a net pressor effect on blood pressure after α-blocker is given, epi's α response is blocked while its β2 response remains leading to net depressor effect on blood pressure (top of image) β2 is Gs coupled, increases cAMP, causes vasodilation α is Gq coupled, increases calcium causes vasoconstriction Epi + β-blocker before nonselective α-blocker is given, epi's net effect is to increase heart rate, contractility, and vasoconstriction leading a net pressor effect on blood pressure after β-blocker given, epi's β response is blocked, while α response remains leading to net pressor effect (bottom of image) Phenylephrine + α-blocker phenylephrine (α1 > α2 agonist) leads to a net pressor effect on blood pressure administration of a nonselective α-blocker leads a net zero effect on blood pressure
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All Videos (0) Pharmacology | Alpha-Blockers Pharmacology - Alpha-Blockers Listen Now 12:21 min 9/11/2021 46 plays 5.0 (1)