Direct Sympathomimetics Direct Sympathomimetics Drug Receptor Selectivity Clinical Applications Epinephrine β > α Anaphylaxis Cardiac arrest Glaucoma (open angle) Asthma and broncho spasms Hypotension Norepinephrine α1 > α2 > β1 Shock Severe hypotension (but ↓ renal perfusion) Causes reflex bradycardia Midodrine Selective α1 agonist Orthostatic hypotension Phenylephrine α1 > α2 Pupillary dilation and glaucoma (wide angle) Vasoconstriction Nasal decongestion Clonidine, α-methyldopa Centrally acting α2-agonists, ↓ central adrenergic outflow Hypertension Does not ↓ blood flow to the kidney Isoproterenol β1= β2 Heart block Dopamine low dose (vasodilation, naturiesis): D1 = D2 medium dose (tachycardia): β1 high dose (vaso- constriction): α1 ,inotropic and chronotropic Shock and ↑ renal perfusion Heart failure Fenoldopam Selective D1 agonist Hypertension Bromocriptine Selective D2 agonist Parkinson's disease Prolactinemia Dobutamine β1> β2, positive inotropic effect Cardiogenic shock Acute heart failure Cardiac stress testing Metaproterenol, albuterol, salmeterol Selective β2 agonists Albuterol and metaproterenol for acute asthma Salmeterol for long-term treatment Ritodrine Terbutaline Selective β2 agonists Reduction of premature uterine contractions Indirect Sympathomimetics Indirect Sympathomimetics Drug Mechanism Clinical Applications Amphetamine Releases stored catecholamines Narcolepsy Obesity Attention deficit disorder Ephedrine Releases stored catecholamines Nasal decongestion Urinary incontinence Hypotension Cocaine Reuptake inhibitor Causes vasoconstriction and local anesthesia