Adrenergic Receptor Agonists Flashcards
Phenylephrine (Neo-Synephrine*)
Alpha-1 selective adrenergic receptor agonist
Activate alpha adrenergic receptors on vascular smooth muscle–> increase BP and TPR
Activate beta receptors only at higher conc
Clinical indications: antihypotensive (hypotension, orthostatic hypotension, shock), paroxysmal atrial tachycardia, nasal decongestant, mydriatic
Clonidine (Catapres)
alpha-methydopa (Aldomet)
Apraclonidine (Lodipine)
Brimonidine (Alphagan)
alpha 2- selective adrenergic receptor agonist
Action: activate central alpha 2 receptors–>decrease central sympathetic outflow–> decrease BP; decrease aqueous humor production–>decrease intraocular pressure
Clinical use: systemic hypertension, glaucoma
Adverse effects: dry mouth, sedation, hypotension
Metaproterenol (Metaprel*)
Beta 2-selective adrenergic receptor agonist
Resistant to methylation by COMT
Clinical use: long-term treatment of COPD, asthma, acute bronchospasm
Terbutaline (Bricanyl*)
Beta 2-selective adrenergic receptor agonist
Not substrate for COMT methylation
Clinical use: long-term treatment of COPD, acute bronchospasm, emergency treatment of status asthmaticus (IV)
Albuterol (Ventolin, Slabutamol)
Beta 2-selective adrenergic receptor agonist
Effects on bronchospasm (dilate smooth muscle) similar to those of terbutaline, oral use, delay preterm labor
Ritodrine (Yutopar*)
Beta 2-selective adrenergic receptor agonist
Developed specifically for uterine relaxant: arrest premature labor, prolong pregnancy
Beta 2-selective adrenergic receptor agonists: adverse effects
tachycardia: pts with coronary artery disease or preexisting arrhythmias–>higher risk; increased risk if MAO inhibitors are used (allow 2-wk elapse)
Increase plasma glucose, lactate, and FFA
Decrease plasma K+–>important in pts with cardiac disease taking digoxin and diuretics
Less likely with inhalation therapy than with parenteral or oral therapy
Fenoldopam (Corlopam*)
D1-selective adrenergic receptor agonist
some stimulation of alpha 2 adrenoceptors–>feedback inhibition of NE release
Effects: renal, mesenteric, peripheral, and coronary vasodilation; renal blood flow is maintained and natriuresis is promoted
Clinical use: hypertensive crisis
Side effect: hypotension
Isoproterenol (Isuprel*)
Non-selective adrenergic receptor agonist
Powerful agonist of all beta receptors (no effect on alpha)
Effects: decrease peripheral resistance, increase HR (arrhythmias), increase myocardial contractility, bronchodilation
Clinical use: bradycardia, AV block, Torsades de pointes
Dobutamine (Dobutrex*)
Non-selective adrenergic receptor agonist
Acts in Beta 1, alpha 2, and Beta2 but mostly Beta 1
Effects: positive inotropic effect on heart, positive chronotropic effect (SA node automaticity, AV conduction), TPR not affected (alpha 1 and beta 1 balance)
Adverse effects: excessive increase in BP & HR, increased ventricular response rate in pts with A-fib, ventricular ectopic activity, increase size of MI, tolerance
Clinical use: short term treatment of cardiac failure, long term efficacy remains uncertain, stress test
Epinephrine (Adrenaline*)
Non-selective adrenergic receptor agonist
Dose and route dependent
Small dose: Beta 1= increase pulse pressure, HR, SV, and CO; Beta 2= decrease TPR
Moderate dose: Beta 1= increase HR, SV, CO, and PP; Beta 2: decrease TPR, DBP; alpha 1: increase TPR, BP
High Dose: alpha 1= increase TPR, BP; potential reflex bradycardia; Beta 1= increase HR, SV, CO, PP; Beta 2= decrease TPR, DBP
Subcutaneous: slow absorption, vasoconstriction
**Epinephrine reversal phenomenon
Different rxns in different vascular beds–>redistribution of blood flow
Adverse effects: headache, tremor, palpitations, cerebral hemorrhage (large dose), cardiac arrhythmias, angina in pts with coronary artery disease
Contraindications: pts using nonselective beta blockers
Clinical use: hypersensitivity rxns (anaphylaxis), cardiac arrest, local anesthetics, post-extubation croup, viral croup
Norepinephrine
Non-selective adrenergic receptor agonist
Beta 1>alpha»»Beta 2
Effects: increase SBP, DBP, PP, coronary flow, TPR; decreases cardiac output, renal blood flow, splanchnic, and hepatic flow
Adverse effects: similar to epinephrine, greater elevation of BP
Clinical use: low blood pressure (dose titration)
Dopamine
Non-selective adrenergic receptor agonist
D1, D2, Beta 1, alpha 1
Ineffective when administered orally
Dose dependent:
Low dose: D2= decrease NE release, alpha adrenergics, stimulation of VSMcs; D1= vasodilation, increase GFR, RBF, Na+ filtration; D1 (renal)= increase proximal, Henle loop [cAMP], decrease Na+-K+ ATPase, Na+ reabsorption
Moderate dose: (+) inotropic effect (Beta 1), release of NE from nerve terminals, tachycardia, increase SBP and PP, no effect on DB or increases slightly, TPR balanced
High dose: vasoconstriction (alpha 1)
**Correct hypovolemia before dopamine use
Adverse effects: tachycardia, anginal pain, arrhythmias, headache, hypertension, extravasation (ischemic necrosis and sloughing
Contraindication: MAO inhibitor or tricyclic antidepressant
Clinical Use: congestive heart failure, cardiogenic and septic shock, acutely improve cardiac and renal function in severely ill
Ephedrine (Ephedrine* Ephedra*)
Mix-acting adrenergic receptor agonist
Indirectly release NE and directly activate receptor
Orally active sympathomimetic drug, found in ma-huang
High bioavailability and long duration of action
Mild CNS stimulant
Pseudoephedrine is used as decongestant
Amphetamine
Indirect acting symathothmimetic amines
Structurally related to NE–>transported by NET1–> displace NE–>NE release independent of exocytosis
Activity affected by rxn affecting storage (reserpine, MAOI, NET1 inhibitors)
Effects: release biogenic amines; stimulate medullary respiratory center; stimulate cortex & reticular activating system–>prevent fatigue, delays need for sleep; tx obesity; activates peripheral alpha ad beta; increases SBP, DBP, & HR; cardiac arrhythmias may occur; increase bladder sphincter contraction–>Tx enuresis & incontinence
