Ch. 15 Adrenergic Agonists and Antagonists

what system do adrenergic agonists/antagonists affect?
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ALPHA-2 receptor location- BLOOD VESSELS - smooth muscle of GI tractStimulation of ALPHA-2 receptors:BLOOD VESSELS: inhibits the release of norephinephrine --> vasoDILATION (decreased vasoconstriction) and decreased BP GI TRACT: decreased peristalsisBETA-1 receptor locationHEART and kidneysBETA-2 receptor locationsmooth muscles of the: LUNG GI TRACT LIVER UTERINE MUSCLEBETA-1 receptor stimulationINCREASED heart rate and contractility - increased renin secretion --> increased BPBETA-2 receptor stimulationLUNG: bronchodilation LIVER: increased blood sugar (increased gluconeolysis) GI: decreased peristalsis MUSC: increased skeletal muscle blood flow UTERUS: decrease in uterine contractionother adrenergic receptorsdopaminergicdopaminergic receptor locationsrenal, mesenteric, coronary, and cerebral *arteriesinactivation of neurotransmitters1. *reuptake back into the neuron 2. enzymatic transformation/degradation 3. diffusion away from receptor2 enzymes that inactivate norepinephrine1. monoamine oxidase (MAO): INSIDE the neuron 2. catechol-O-methyltransferase (COMT): OUTSIDE the neurondirect-acting sympathomimeticsdirectly stimulate adrenergic receptors (epinephrine and norepinephrine)indirect-acting sympathomimeticsstimulate the release of norepinephrine from the terminal nerve endings (e.g. amphetamine)mixed-acting sympathomimeticsstimulate adrenergic receptor sites & stimulate the release of norepinephrine from the terminal nerve endings (e.g. ephedrine, pseudoephedrine)how is pseudoephedrine classified as a symphathomimetic?mixed-acting sympathomimetic acts indirectly by stimulating release of norepinephrine and acts directly on alpha-1 and beta-1 receptorspseudoephedrine effectsincreases heart ratepseudoephedrine contraindications- hypertension - closed-angle glaucoma - bronchitis - emphysema - urinary retention *use w/ caution in diabeticscatecholamineschemical structures of a substance (endogenous or synthetic) that can produce a sympathomimetic responseEndogenous Catecholaminesepinephrine, norepinephrine, dopamineSynthetic catecholaminesIsoproterenol Dobutaminenoncatecholaminesphenylephrine, metaproterenol, albuterolnoncatecholamines stimulate __________________ receptorsadrenergicside effects of adrenergic AGONISTSHypertension Tachycardia Palpitations Restlessness Tremors Dysrhythmias Dizziness Urinary retention Nausea vomiting Dyspnea Pulmonary edemaalbuterol sulfate (receptor, selectivity, and response)SELECTIVE for BETA-2 receptors (lungs and uterus) response: relation of bronchial smooth muscle and bronchodilationAlbuterol side effectstachycardia palpitations dizziness dysrhythmias nausea vomiting urinary retentionwhat receptor(s) does epinephrine act on?alpha-1, beta-1, beta-2 (nonselective)Effects of epinephrine- Increased BP and cardiac output - increased HR, tachycardia - mydriasis - bronchodilation - renal vasoconstriction --> decreased urinary outputEpinephrine therapeutic usestreat nasal congestion allergic rxn asthma exacerbation bronchospasm angioedema status asthmaticus cardiac arrest cardiac resuscitationepinephrine routes of adminstrationIM, IV, endotracheally t 1/2 = <5 min IVEpinephrine Contraindicationscardiac dysrhythmias cerebrovascular disease closed-angle glaucoma hypertension pulmonary edema cardiac disease hyperthyroidism diabetes mellitus renal dysfunction pregnancyEpinephrine side effectsnausea vomiting restlessness tremor agitation sweating headache pallor oliguria weakness dizziness hyper/hypoglycemia paresthesiaAntidote for epinephrinePhentolaminethings that increase the effects of ephinephrinedecongestants (additive effect) tricyclic antidepressants (TCAs) monoamine oxidase inhibitors (MAOIs)Clonidine (receptor, selectivity, response)SELECTIVE ALPHA-2 AGONIST: central acting (stimulates alpha-2 receptors in CNS) response: inhibit release of norepinephrine --> decrease in BPClonidine Therapeutic UseshypertensionClonidine side effectsbradycardia hypotension sedation dry mouthMethyldopa (receptor, selectivity, response)(selective?) ALPHA-2 AGONIST: centrally acting response: inhibits release of norepinephrine --> vasodilation --> decrease in BPside effects of central acting alpha-adrenergic agonistsheadache nasal congestion drowsiness nightmares constipation edema ED elevated liver enzymesNONSELECTIVE adrenergic AGONISTS- Epinephrine (b1,2) - Ephedrine hydrochloride or sulfate (a1,b1,2) - Norepinephrine (a1,b1) - dopamine hydrochloride (a1,b1) -pseudoephedrine hydrochloride* (a1,2,b1) all used mainly for hypotension**SELECTIVE alpha-1 AGONISTS- midodrine* - pheylephrine hydrochloride* (sinuses and nasal congestion) * = hypotensionSELECTIVE beta-1 AGONISTdobutamine hydrochloride for HF, cardiogenic shock, cardiac surgerySELECTIVE beta-2 AGONIST- albuterol* - metaproterenol - terbutaline sulfate used for bronchospasmsEffect of alpha-1 BLOCKERS- vasodilation --> decreased BP (reflex tachycardia may result) - mydriasis (constriction of pupil) - ejaculation supression - relaxed bladder and prostateEffect of beta-1 BLOCKERS- decreases HR and contractionsEffect of beta-2 BLOCKERS- constricts bronchioles - contracts uterus - inhibits glyconeolysis (decreases blood sugar)alpha antagonists- selective (block alpha-1) - non selective (block alpha-1 and alpha-2)alpha antagonists effectsvasodilation --> decreased BPalpha antagonists side effectsorthostatic hypotension, reflex tachycardia, dizzinesstherapeutic uses of alpha antagonistsraynaud disease benign prostatic hyperplasia (BPH)SPECIFIC alpha BLOCKERS (alpha-1 blockers)- phentolamine mesylate* (antidote for dopamine, dobutamine, pheylephrine, epinephrine, norapinephrine, and catecholamine extravasation - doxazosin mesylate* (BPH) - prazosin hydrochloride* - terazosin hydrochloride* * = used for hypertensionBeta blockers- selective (block beta-1) - nonselective (block beta-1 AND beta-2)therapeutic uses of beta blockershypertension, heart failure, angina, MIEffects of beta blockersdecrease heart rate, decrease BPside effects of beta blockersbronchoconstrictioncontraindications of beta blockersasthma *use w/ caution in pts with COPDPropranolol Hydrochloridenonselective; first beta blocker prescribed to treat angina, cardiac dysrhythmia, hypertension, and heart failure **also used for migraine prophylaxisInstrinsic Sympathomimetic Activitythe ability of certain beta blockers to bind with a beta receptor to prevent strong agonists from binding to that receptor producing complete activationAtenolol (selectivity, receptor, effects)SELECTIVE beta-1 BLOCKER effects: suppresses the renin-angiotensin-aldosterone system (RAAS), decreases HR and BP by decreasing peripheral vascular resistanceSELECTIVE beta-blockers (beta-1)- metoprolol - atenolol* - acebutolol hydrochloride - betaxolol - bisoprolol fumarate - esmolol hydrochloride all used for hypertensionNONselective beta blockers- Nadolol* - Pindolol* - Sotalol (dysrythmias) - Timolol maleate* * = used for hypertensionAtenolol contraindicationsbradycardia heart block cardiogenic shock acute heart failure asthma sick sinus syndrome *use w/ caution in pts w/ COPD *electrolyte imbalances should be corrected before useAtenolol pharmacokineticsdistribution: can cross BBB absorption: 50-60% in GI tract; PB 10% t 1/2: 6-7 hrs excretion: urineAtenolol pharmacodynamicstablet or IV onset 1 hr; peak 2-4 hrs; duration 24 hrsAtenolol interactions- NSAIDs (decrease hypotensive effects of atenolol) - increased absorption with atropine - increased hypoglycemia with insulin and sulfonylureas - effects are potentiated w/ other hypertensivesside effects of Atenololbradycardia hypotension headache dizziness cold extremities bronchospasm cardiac dysrhythmias flushing fatigue ED depressionNONSPECIFIC adrenergic BLOCKERS- carvedilol - labetalol - propranolol hydrochloride all used for hypertensionadrenergic neuron antagonists (adrenergic neuron blockers)drugs that block the release of norepinephrine from the sympathetic terminal neuronsreserpine- adrenergic neuron blocker - antihypertensive - depletes serotonin, causes severe depression