Adrenergics _26 Adrenergic Blockers.

Adrenergics and Adrenergic Blockers I. Adrenergics/ Sympathomimetics  mimic effects of NE by stimulating SNS. A. Effects of Adrenergics at receptor sites Alpha 1 Receptors  vasoconstriction (skin & mucous membrane)  increase BP  pupil dilation  closure of urinary bladder sphincter  thickened salivary secretions  goosebumps  ejaculation Alpha 2 receptors  decrease NE release  decrease BP  decrease GI motility Beta 1 receptors     increase HR Increase cardiac contraction increase cardiac conduction lipolylis Beta 2 receptors       bronchodilation vasodilation (skeletal muscle) relaxation of uterus relaxation of GIT & decrease GI secretions relaxation fo urinary bladder increase blood sugar B. Inactivation of NE: 1. reuptake of NE back into the neuron. 2. enzymatic degradation - MAO & COMT 3. diffusion away from transmitter C. Classification of Adrenergics/ Sympathomimetics I. Direct Acting Adrenergic  epinephrine Indirect Acting Adrenergic  amphetamine Mixed Acting Adrenergic  ephedrine II. III. A. Nonselective Adrenergics  endogenous catecholamines  epinephrine*  norepinephrine  dopamine  synthetic catecholamine  dobutamine Epinephrine Indications: tx of allergic reaction, anaphylaxis, bronchospasm, cardiac arrest. Mechanism of Action (MOA):  acts on alpha 1 , to increase vasoconstriction & BP  acts on beta 1, to increase heart rate  acts on beta 2, to promote bronchodilation B. Alpha selective- adrenergics  Alpha 1 & 2 adrenergic  phenylephrine*  Alpha 2 adrenergics  clonidine  methyldopa phenylephrine Indications: Tx of cold & allergies, shock MOA: alpha adrenergic that causes vasoconstriction & increase BP C. Beta selective adrenergics  Beta 1 & 2 adrenergics (beta agonists)  Isoproterenol*  ritodrine  Beta 2 selective adrenergics  terbutaline  albuterol Isoproterenol Indications : tx of congestive heart failure, asthma MOA: beta adrenergic, increases heart rate & contractility & bronchodilation  Common S/E & adverse reactions of adrenergics:  hypertension  tachycardia , palpitations & tremors  dizziness  urinary retention  pallor  nausea & vomiting ( N & V)  blood glucose may increase  Lifethreatening effect: cardiac dysrhythmias II. Adrenergic Blockers/ Sympatholytics  block alpha & beta receptors, blocking sympathetic responses A. Effects of adrenergic blockers at receptor sites: Alpha 1 receptor      vasodilation & decrease BP reflex tachycardia miosis suppress ejaculation reduce contraction of bladder sphincter & prostate gland Alpha 2 receptor Beta 1 receptor  decrease HR & contraction Beta 2 receptor  bronchoconstriction  uterine contraction  decrease blood sugar C. Classification of Adrenergic Blockers/ Sympatholytics  Direct Acting  Indirect acting A. Alpha & Beta adrenergic Blockers (Nonselective Adrenergic blockers)  carvedilol  labetolol* indications: tx of hypertension & angina pectoris MOA: blocks alpha & beta receptors in SNS causing decrease BP without reflex tachycardia & decrease renin B. Alpha 1 selective adrenergic blockers  phentolamine*  doxazosin  prazosin Indications: Tx of peripheral vascular disease, pheochromocytoma, acute HPN, benign prostatic hypertrophy MOA: blocks alpha 1, producing vasodilation & decrease BP & decrease contraction of prostate SE/ Adverse effects of alpha blockers:  flush & nasal stuffiness  orthostatic hypotension & dizziness  reflex tachycardia Lifethreatening effect: cardiac dysrhythmias C. Beta 1 and 2 adrenergic blockers (Nonselective beta blockers)  propanolol*  sotalol  timolol  nadolol  pindolol propanolol Indications: Tx of cardiac dysrhythmias, HPN, angina, myocardial infarction (MI) MOA: blocks beta 1 & 2 adrenergic receptors, causes decrease HR & BP as well as bronchoconstriction & uterine contraction S/E & Adverse effects of beta blockers:  bradycardia  hypotension & dizziness  headache  hypoglycemia  visual hallucinations & mood changes  thrombocytopenia Lifethreatening effects: laryngospasm, heart block D. Beta 1 selective adrenergic blockers  metoprolol*  atenolol  acebutolol  esmolol  bisoprolol  betaxolol  esmolol Indications: Tx of HPN, angina pectoris , myocardial infarction MOA: blocks beta 1, to decrease HR & BP  Alpha blockers (ie prazosin) & beta blockers (ie propanolol, metoprolol, pindolol)  may cause impotence or decrease in libido E. Adrenergic Neuron blockers  guanethidine  guanadrel Whatsoever you sow, that you shall reap.