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49 Cards in this Set
- Front
- Back
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Describe the structure of Catecholamines.
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Catechol (3,4-dihydroxybenzene) & an ethylamine group (2 carbon side-chain w/ terminal amine
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What are the catecholamines?
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NE, eprinepherine, dopamine, & isoproterenol
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How are the stereoisomers of NE, ephinephrine, & isoproterenol?
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Results from a hydroxyl group on the beta carbon. The levo isomers of NE are more potent than the dextro isomers
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Describe the structure of non-catecholamine.
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Have substitutions on the benzene ring, the alpha & beta side chain carbons & the terminal amino group. The benzene rings may be replaced totally by other structures
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What factors does the structure of compounds confer?
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Whether the drug is directly or indirectly acting, has receptor selectivity, has CNS effects, & how its metabolized
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How does size of alkyl group in amino acid substitution affect receptor activity?
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Larger size alkyl group = greater Beta receptor activity (NE<Epi<Iso)
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What group substitution decreases potency?
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Substitution of benzene ring; absence of -OH group @ 3,4 position decreases potency
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What group substitution alters duration of action?
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Substitution of alpha carbon
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What is needed for substitution of beta carbon?
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Need the -OH group to be direct acting agonist
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What are the mechanisms of action for adrenomimetic drugs?
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Direct acting, receptor selectivity, & response depends on selectivity of receptors
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What is the mech of alpha-1 receptors?
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Gq->PLC->inc Ca levels
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What is the mech of alpha-2 receptors?
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Gi-> inhibits adenylate cyclase-> decrease cAMP
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What is the mech of beta receptors?
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Gs-> stimulates adenylate cyclase-> inc cAMP
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What are direct acting sympathomimetics?
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Interact w/ & stimulate adrenergic rectors (a1, a2, b1, b2)
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What are the charac of direct acting symp?
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Have high affinity for all adrenoceptors subtypes (eg epi), whereas others are more selective. The response of a given tissue to ea agent depends upon charac of the agonist, the predom receptor, & reponses elicite by stim of available receptors
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What are the mixed agonists?
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NE & epi
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What is epi receptor affinity?
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Affinity for all receptors. B2 action more evident @ low dose. Higher levels constrict all vessel via alpha
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What is NE receptor affinity?
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Alpha & Beta-1 (no beta-2)
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What are the charac of indirect acting sympathomimetics?
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Release NE from nerve terminals & elicits similar effects. Some require neuronal & vesicular transport to enter neuron, often produces tachyphylaxis w/ dec NE, can work in combination w/ direct sym, can result in desensitization
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What drugs reduce the effects indirect sympathomimetics?
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Resperpine, guanethidine, cocaine, or tricyclic antidepressants
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What is an example of a indirect acting sympathomimetic?
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Tyramine
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What are the charac of Tyramine?
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Action via release of NE from nerve terminal-> inc BP & HR. In foods (red wine, aged cheese, soybeans, avocados, pickled fish). Some believe it to be a neurotransmitter since binds to a receptor. Caution w/ patients taken MAO inhib
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What is an example of a mixed acting sympath?
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Ephedrine
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What are the charac of ephedrine?
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Similar structure to amphetamine & methamph. Agonst @ a1=a2, b1=b2. Releases NE from terminal. Can give po. Addictive so no longer used as decongestant in asthmatics (can convert to methamph.
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What is pseudoephedrine?
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One of the 4 ephedrine enantiomers. Limited availability OTC. Common ingredient in cold meds (Sudafed)
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What is the general distribution of adrenergic receptors?
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alpha=constriction. Beta=dilation. NE w/ little effect on b2 receptors so have min effect on bronchial smooth muscle
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What are the effects of pure alpha stim on the CV system?
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Constricts vessels, inc TPR, reduces flow, inc BP, relfex dec HR. Little direct effect on heart b/c no alpha receptors (eg phenylephedrine)
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What are the effects of pure beta stim on the CV system?
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Dilate skeletal m. blood vessels (b2), dec TPR, inc flow, dec BP, inc HR (b1)
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What are the effect of adrenergic stim on the eye?
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a1=mydriasis, a2=dec production of aq humor, & inc outflow. Beta= inc aq humor production (inc pressure)
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What are the effects of adrenergic stim on the Respiratory system?
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b2 agonists= relax bronchial smooth m. & reduce leukotriene/histamine release from mast cells. a1=mediates decongestant action; constricts blood vessels in the repiratory tract
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What are the effects of adrenergic stim on the GU system?
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Used to treat incontinence; b2 relaxes detrusor m. & a1 contracts trigone sphincter. Targets uterus; response depends on endocrine balance, b2 agonist relaxes in late pregnancy (eg ritodrine)
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What are the effects of adrenergic stim on the GI system?
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Motility reduced while sphincters contract. Transient effect w/ little therapeutic value
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What are the effects of adrenergic stim on the urinary bladder?
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a1= slightly contracts sphioncter. B2=slightly relaxes detrusor m.
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What are the effects of adrenergic stim on the CNS?
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Lipophillic agents produce stim effects. Slight stim w/ epi, NE, & iso even though they don't readily pass BBB
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What are the effects of adrenergic stim on metabolism?
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Inc O2 consumption, stim glycogenlysis (b2). Lipolysis: b3=inc lipolysis, a2= inhibits lipolysis. Insulin: b2=inc insulin, a2=dec insulin release
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What are the clinical uses of beta adrenoreceptor mediated actions?
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Relieve bronchoconstriction (b2)- albuterol, restores heart activity post MI (b1)- iso or epi, suppresses premature labor (b2)
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What are the clinical uses of alpha adrenoreceptor mediated actions?
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Reduce diffusion of infiltrating anesthetics (epi), homeostasis (epi), maintain BP if CO & perfusion are intact, nasal decongestant (phenylephi), mydriatic (phenylephi), anaphylaxis (epi), narcolepsy (amphetamine/modafinil), & glaucoma
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What is brimonidine?
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New selective a2>>>a1 agonist. Dec aq humor & in outflow to dec presure
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What are the clinical uses of amphetamines?
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Indirectly acting. Treat nacolepsy & min brain dysfunction; central acting drugs required (eg amphet or modafinil)
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What are the clinical uses of Clonidine, guanfacine, & quanabenz?
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a2 agonists. Treat hypertension, ADHD, & dec NE release via presynaptic receptor binding
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What are the side effects of adrenoreceptor agonists?
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Palpitations, anxiety, fear, insomnia, headache, nausea, vomiting, sweating (apocrine glands-a1)
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What are the contraindications of adrenoreceptor agonists?
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W/ patients w/ hyperthyriodism, severe hypertension, cardiac disease, glaucoma patient using beta agonists. Drug interaction when used w/ halogenated hydrocarbon anesthetics, oxytoxic drugs, MAO inhibitors, catecholamine reuptake inhibitors.
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What is dopamine?
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A naturally occuring precursor to NE & epi. CNS neurotransmitter.
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What are the effects of dopamine?
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D1=D2>>b1>>a. Dec release of NE (via D2 presynaptic receptors), interacts w/ alpha & beta 1 receptors, interacts w/ peripheral dopamine receptors. Doesn't cross BBB
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What are the clinical affects seen w/ low dose of dopamine?
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Low doses elicit vasodilation in renal, mesentery, coronary, & intracerebral vascular bed (D1). Little effect on heart.
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What are the clinical affects seen w/ high dose of dopamine?
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Higher doses inc HR & contractility. Contractility >HR. Small inc in O2 demand compared to epi (no b2 so no vasodilation or reflex effects). Alpha mediated vasoconstriction.
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What drug is useful in shock?
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Dopamine used via iv infusion can enhance renal perfusion or as a + inotropic agent.
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What is Fenoldopam?
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D1 selective agonist. Leads to arterial vasodilation (renal, mesentery, coronary); used in severe hypertensive situations. Stim naturesis. T1/2= 10 min
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What is Dobutamine?
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B1>B2>>>>a1. Inc CO & SV w/o marked inc in HR. t1/2= 2min. Use caution w/ glaucoma patients.
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