Non-Selecting Direct acting Adrenergic agonists Flashcards
ISOPROTERENOL (isuprel)
Beta 1 and 2 Agonist (NO EFFECT ON ALPHA RECEPTORS)
- EFFECTS:
–> decrease TOTAL PERIPHERAL RESISTANCE
–> INCREASE HR (arrhythmias
–> INCREASE Myocardial CONTRACTILITY
–> BRONCHODILATION
- USES: Bradycardia, A-V block, TORSADES DE POINTES
DOBUTAMINE (dubutrex)
Beta 1. Beta 2, Alpha 1 (MAINLY ACTS ON Beta1 at therapeutic dose)
EFFECTS:
–> positive inotropic effect on heart (B1)
–> positive chronotropic effect (SA node automaticity, A-V cond)
–> Total peripheral resistance not affected (alpha1 - Beta2 balance)
USES: short term tx of cardiac failure
ADVERSE EFFECTS:
–> excessive increase in BP and HR, increased ventricular response rate, ventricular ectopic acitivty, may increase size of MI
–> Tolerance may develop (SHORT TERM USE)
EPINEPHRINE (Adrenaline)
- Potent ALPHA and BETA RECETPOR STIMULANT
- Dose/administration route-dependent
- SUBCUTANEOUS: Slow absorption and causes vasoconstriction
describe the dose responses to intravenous epinephrine
- SMALL DOSE: (DECREASE MAP)
–> Beta 1 = Increase pulse pressure (PP), Increase HR, SV, CO
–> Beta 2 = Decrease total peripheral resistance
- MODERATE DOSE: (increase MAP)
- -> Beta 1 = increase HR, SV, CO, PP
–> Beta 1 = Decrease TPR, DBP
–> Alpha 1 = INCREASE TPR, BP
- HIGH DOSE: (INCREASE MAP, BP)
–> Alpha 1 = INCREASE TPR, BP
–> potential reflex bradycardia
–> Beta 1 and 2 = lesser effects
describe the Vascular effects of epinephrine
- MAIN SITE of ACTION = SMALLER ARTERIOLES and PRECAPILLARY SPHINCTERS
- CAUSES A REDISTRIBUTION OF BLOOD FLOW
–> cutaneous blood flow DECREASES
–> Skeletal muscle blood flow INCREASES
–> Renal blood flow DECREASES; FF INCREASES, RENIN SECRETION INCREASES (Beta1)
–> pulmonary blood flow: PAP and PVP INCREASES
–> coronary blood flow INCREASES
–> Cerebral circulation has LITTLE EFFECT AT THERAPEUTIC DOSE
Describe the epinephrine reversal phenomenon
- alpha receptor antagonism causes INCREASE epinephrine induced VASODILATION –> DECREASE TPR –> DECREASE MAP
- Beta receptor antagonism –> Ephinephrine induced vasoconstriction unmasked –> INCREASE MAP
describe the cardiac effects of epinephrine
- POWERFUL CARDIAC STIMULANT (Beta 1)
- Heart rate INCREASES, shorted systole, diastole lengthens
- Increase Inotropy, lusitropy and chronotropy RESULTING IN INCREASE MYOCARDIAL OXYGEN CONSUMPTION
- Increase automaticity –> potential arrhythmias
describe the toxicity and adverse effects of epinephrine
- thobbing headache, tremor, and palpitations
- cerebral hemorrhage (large doses, rapid IV)
- Cardiac arrhythmias
- angina in patients with coronary artery disease
CONTRAINDICATIONS
–> PATIENTS USING NONSELECTIVE BETA BLOCKERS (cause severe vasoconstriction (epinephrine reversal)
what are the therapeutic uses of epinephrine
- Hypersensitivity reactions, including anaphylaxis
- cardiac arrest
- ingredient in local anesthetics
- post-extubation croup, viral croup
describe properties of Norepinephrine
- equipotent to epinephrine in stimulating BETA 1 RECEPTORS
- POTENT ALPHA AGONIST (mroe so than epinephrine)
- LITTLE ACTION ON BETA 2 RECEPTORS
describe the effects of norepinephrine
- INCREASE Systolic BP, Diastolic BP, PULSE PRESSURE
- INCREASE CORONARY FLOW (coronary dilation + elevated BP)
- unchanged/decreased cardiac output (decreased HR overcoming increased stroke volume
- INCREASE TOTAL PERIPHERAL RESITSANCE (TPR)
- Decrease renal blood flow
- decrease splanchnic and hepatic blood flow
- USES: tx of LOW BLOOD PRESSUE
describe the toxicity/adverse effects of norepinephrine
- same as epinephrine
–> restlessness, headache, tremor, palpitations
–> cerebral hemorrahge
–> cardiac arrhythmias
- angina in patients with coronary artery disease
- GREATER ELEVATION OF BLOOD PRESSURE
DOPAMINE
D1, D2, Beta 1 and alpha 2
- immediate metabolic precursor of norepinephrine and epinephrine
- in CNS: NT particularly important in the regulation of movement
- in periphery: synthesized in epithelial cells of the proximal tubule –> local diuretic and natriuretic effects
- is a substrate for both MAO and COMT –> ineffective when administered orally
Describe Dose response of DOPAMINE
- LOW DOSE:
–>Presynaptic D2 receptor = Decrease NE release and alpha adrenergic stim
–> Vascular D1 receptors = vasodilation (incrase GFR, RBF) –> decrease Na reabsorption
–> Renal tubular cell (D1) = Increase Na Filtered
–> END RESULT Na+ Diuresis
- MODERATE DOSE
–> POSITIVE INOTROPIC EFFECT (Beta 1)
–> NEGATIVE Systolic BP and pusle pressure
–> Total peripheral resistance UNCHANGED
- HIGH DOSE
–> GENERAL VASOCONSTRICTION (alpha 1)
Adverse reaction/ precautions of DOPAMINE
- Hypovolemia should be corrected before dopamine use
- Tachycardia, anginal pain, arrhythmias, headache, hypertension
- Extravasation –> Ischemic necrosis and sloughing
- MAO inhibitor or tricyclic antidepressant: avoid DOPAMINE or use extreme caution
–> MAO inhibitors will inhibit degradation of dopamine
