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29 Cards in this Set
- Front
- Back
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Sympathomimetics
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Drugs that evoke physiological responses similar to those produced by endogenous activity of the sympathetic nervous system.
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Alpha adrenergic antagonists
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Bind selectively and interfere with the ability of catecholamines or sympathomimetics to cause an alpha response.
Reduce Insulin secretion HypoTN Tachy - baroreceptor mediated Maximal cardiac stimulation from NE without Beta block |
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Phentolamine
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Competitive Alpha Antagonist 1&2
Allows more NE release (blocking A2) Causes drop in peripheral BP Treats pheochromocytoma (short acting) Given SQ for extravasation of vasopressor |
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Prazosin
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Selective Alpha 1 Antagonist
No NE effects Dilates arteries and veins No reflex tachy |
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Phenoxybenzamine
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Irreversible Nonselective Alpha Antagonist
Cannot be overcome until metabolized (24 hours) Used to tx Pheochromocytoma until surgery As surgery approaches dc 24 hours in advance Use shorter acting during surgery until tumor out |
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Pheochromocytoma
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Tumor of the adrenal glands that produces excessive Norepi and Epi in the blood stream.
Usually HTN |
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When treating a pheochromocytoma in what order should you block Alpha and Beta receptors?
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Alpha then Beta
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B1 receptors
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Heart, Kidneys
Increased HR and CO Renin release - fluid retention 1 heart |
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B2 receptors
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Smooth muscles of the bronchioles,
bronchodilates 2 lungs |
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Norepinephrine
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Potent Alpha Agonist A1 and B1
Increased SVR, MAP Vasoconstriction at the muscles, kidneys, liver Can cause brady, anxiety, RR difficulty, severe HTN in HTN pt's, CP, pallor, sweating Use to tx: Septic shock, HypoTN Catecholamine |
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Epinephrine
What is different than the others? |
Direct Acting A1 and B12 beta stimulation
Rapid onset, brief duration B>A **Given IV, IM, ET, Topically** Reduces renal flow, increases BG, lowers insulin, Drive K into skeletal muscle cells increases factor 5 - coags Catecholamine |
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What is an interesting drug that can be used to treat a Beta 2 OD?
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Glucagon
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Dopamine
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Synthetic Catecholamine
Dose dependent low = 3 mcg/kg renal dose dopamine mid= 3-10 mcg/kg B1 and some NE High= 10-20 mcg /kg B&A > 20 mcg/kg A1 |
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Adverse affects of Dopamine
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Extravasation
N/V HTN Dysrhythmias |
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Fenoldopam
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Selective D1 Agonist Synthetic Catecholamine
Used like renal dose dopamine - no change in BP Vascular likes it to dilate vessels they are working on Higher doses have antihypertensive effects |
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Isoproterenol
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Think RATE Synthetic Catecholamine
Chemical pacemaker Similar to epi but beta dominate Rapid metabolism by COMT Used on denervated hearts |
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Effects of Isoproterenol
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Bronchodilation
Reduces SVR Decreased MAP Increased myocardial O2 requirements No baroreceptor brady |
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Dobutamine
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Synthetic Catecholamine
Treats shock and low CO states No change in SVR (that why we love it) Inotropic and chromotropic effects Short half life |
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Dobutamine cautions
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Can drop MAP if vasodilation occurs
Can increase myocardial o2 consumption if tachy occurs **Tachyphylaxis** |
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Indirect acting sympathomymetics
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Typically dont have a direct effect
Often cause the release of epi and norepi Some of them do have direct effects |
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Ephedrine
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Indirect Acting like epi but less intense
Lasts 10 times longer Increases HR, BP, and CO Bronchodilates |
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Ephedrine uses and cautions
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40% eliminated unchanged in the kidneys
Can be given IM, PO **Tachyphylaxis** Adverse drug interactions with MAOIs Can treat bronchospasm Careful with CAD and previous BB |
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Phenylephrine
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Indirect acting but direct acting A1 constricts venous and arteries - increased BP and preload
Can cause reflexive brady Acts like NE but less potent and longer acting |
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Phenylephrine CV effects
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Increased SBP and DBP
Increased myocardial O2 consumption reduced renal and splanchnic flow Can slow a tachy HR Eliminated :liver |
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Phenylephrine cautions
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Slow HR - heart block possible
peds asystole with nasal use CHF If you have spinal hypotension not a good drug of choice - use epi Use ephedrine if brady happens Use caution with TCA / MAOI Extravasation a concern |
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Metaraminol
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Lesser known drug
Indirect acting and direct acting actions A and B Intense vasoconstriction |
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Amphetamine
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Indirect acting
Resembles ephedrine alpha and beta stimulation Crosses BBB = CNS stimulation Tachyphylaxis & Dependence common Never used in anesthesia Can affect MAC - chronic needs less, acute needs more |
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Methoxamine
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Acts directly / selectively on Alpha
arterial vasoconstriction - doesnt effect preload = good for CHF pt Has antiarrhythmic effects - which might be good for someone having dysrhymias on epi |
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Phosphodiesterase Inhibitor
Example: |
The backdoor to the receptor. They cross the cell wall and increase cAMP causing the effects of a typical G protein receptor.
Example: Milrinone |
