Adrenergic Flashcards
NE activates which receptors?
alpha-1, beta-1, and alpha-2
Epi activates which receptors?
alpha-1, beta-1, and beta-2
Reserpine
Indirect inhibitors of SNS NT
Depletes monoamine NT from PNS/CNS terminals (Epi, NE, DA, 5-HT) by inhibiting uptake of synaptic vesicles. Can cause severe depression by crossing BBB. Rarely used due to side effects.
Guanethidine
Indirect inhibitors of SNS NT
Displaces catecholamine in synaptic vesicles, eventually leading to depletion and replacement of NT. No CNS activity/does not cross BBB. Minor: blockade of post-synaptic receptors and reuptake.
Bretylium
Indirect inhibitors of SNS NT
Blocks depolarization-induced NE release. No CNS activity/does not cross BBB. Pronounced membrane stabilization–local anesthetic effect. Used to treat v-fib and dysrhythmias.
Ephedrine, Pseudoephedrine
Indirect sympathomimetic
Action in part due to release of NE, causing mild cardiac stimulation, decongestion. Pseudoephedrine OTC or Rx depending on state–easily made into methamphetamine.
Amphetamine, Methylphenidate
Indirect sympathomimetic
Most of action due to release of NE. Used to treat ADHD, but also widely used illicitly. High doses lead to pronounced cardiac stimulation.
–nidine drug ending indicates:
alpha-2 agonist, direct sympathomimetic
–terol drug ending indicates:
beta-2 agonist, direct sympathomimetic
–osin drug ending indicates:
alpha-1 antagonist, direct sympathomimetic
–olol drug ending indicates:
beta antagonist, direct sympathomimetic
–stigmine drug ending indicates:
AChE inhibitor, direct sympathomimetic
Isoproteronol
Beta-agonist (nonselective). Treats bradycardia, used in ICU and OR. Also produces profound vasodilation (reflex tachycardia).
Albuterol, terbutaline, levalbuterol, salmeterol
Beta-2-agonist. Preferential activity for smooth muscle.
Dobutamine
Beta-1-agonist. Increases HR and contractility with less vasoconstriction. Used primarily for cardiogenic shock IV in ICU.
Therapeutic use: Asthma, COPD
Beta-2-agonists: bronchodilators (SM relaxation –> opening of the airways). Terbutaline, albuterol, salmeterol, levalbuterol)
Therapeutic use beta-agonist: cardiac
Isoproterenol: cardiac stimulant used to overcome bradycardia and some specific arrhythmias.
Dobutamine: cardiac stimulant used in cases of acute CHF and MI. Some alpha agonist activity.
Adverse effects of beta-agonists
Severe tachycardia (overstimulation SA node) Cardiac arrhythmias (decreased electrical stability) Angina pectoris (cardiac stimulation --> increased O2 demand. In extreme cases, can lead to necrosis of cardiac tissue and MI) Skeletal muscle weakness (promotes K uptake --> hyperpolarization --> muscle weakness)
Propranolol
Beta-blocker (nonselective). Poor bioavailability. Decreased liver function can lead to high blood levels and increased toxicity.
Atenolol, Bisoprolol, Metoprolol
Beta-1-antagonists
Esmolol
Beta-1-antagonist. Very short half-life in plasma. Used IV in ICU settings (quickly is out of system if bad reaction).
Carvedilol, Labetalol
Mixed antagonists against beta-1, beta-2, and alpha-1. Produces a smaller increase in peripheral vascular resistance by relaxing vascular smooth muscle. This vasodilating effect is desirable in HTN and CHF treatment.
Adverse effects beta-antagonists
Generally fall into one of two categories:
- bronchoconstriction due to blockade of beta-2 receptors of bronchial SM
- severe bradycardia heart block due to over-blockade of cardiac beta-1 receptors
–olol drug ending indicates:
pure beta-blockade
–alol or –ilol drug ending indicates:
mixed blockade function. Beta-blockage and something else
Peripheral alpha-1- and -2-agonists:
Increase vasoconstriction. Used topically, in injections, and IV
Central alpha-2-agonists:
Decrease sympathetic tone, slow HR, decrease CO, decrease vasoconstriction
Methoxamine, phenylephrine
Pure alpha agonist (1>2). Methoxamine is used for the treatment of acute hypotensive crisis (produces reflex baroreceptor bradycardia (diving reflex, decreased HR). The heart only has beta-1 receptors, so the bradycardia is an indirect effect of this drug.
Norepinephrine
Stimulates alpha and beta-1 receptors. Net effect of vasoconstriction and increased HR and contractility. (Weak beta-2 stimulant)
Phentermine
Alpha>beta agonist. Used in weight loss alone or in combination with topiramate
Clonidine
Selective central alpha-2-agonist. HTN med.
Methyldopa
Prodrug, acts centrally. Net effect of decreased sympathetic outflow. Converted to active methyl-NE in the CNS.
Adverse effects when active drug enters systemic circulation, including HTN, coronary ischemia, cerebral ischemia, and local necrosis at injection site.
Therapeutic uses of alpha-agonists:
Nasal congestion (Constriction of blood vessels in nasal mucosa counteracts swelling and congestion of nasal passages) Local anesthetics (Vasoconstriction of vessels at site of injection, prolongation of anesthetic affect) Ocular preparations (Constriction of vessels on surface of eye --> decreased redness) Anaphylactic shock (Epi reverses hypotension [alpha-1] and bronchoconstriction [beta-2], and inhibits histamine release by mast cells [beta-2])
Adverse effects of alpha-agonists
Hypertension (vasoconstriction of arterial SM [alpha-1]) Myocardial necrosis/infarction (extreme alpha-mediated vasoconstriction of coronary arteries) Cerebrovascular accident (alpha-mediated constriction of cerebral vessels)
Epinephrine
Potent cardiac stimulant (beta-1) and vasoconstrictor (alpha-1).
Effect is dose dependent: Beta receptors are more sensitive than alpha, so at low doses they are preferentially stimulated. At high doses, however, the alpha effect can override the beta. Therefore, a biphasic response can result following epi injection (high dose effect at first, low dose effect as epi is metabolized).
Effects on the heart by epinephrine
Stimulates beta-1 receptors = cardiac stimulant. Increased HR, conduction velocity, ventricular contraction.
Effects on vascular SM by epinephrine
Effects are dependent on several factors, including the dose, route of admin, type of receptors predominating in a given vascular bed. Therefore, effect of epi in a given situation is very difficult to predict.
Phentolamine, Pheonxybenzamine
Alpha-1 and -2 non-selective antagonists. Used for special situations: pheochromocytoma, Reynaud’s syndrome.
Doxazosin, Prazosin, Tamsulosin, Terazosin
Alpha-1 antagonists. Tamsulosin is used more to treat prostatic hypertrophy.
