Non-Selecting Direct acting Adrenergic agonists Flashcards

1
Q

ISOPROTERENOL (isuprel)

A

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
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2
Q

DOBUTAMINE (dubutrex)

A

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)

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3
Q

EPINEPHRINE (Adrenaline)

A
  • Potent ALPHA and BETA RECETPOR STIMULANT
  • Dose/administration route-dependent
  • SUBCUTANEOUS: Slow absorption and causes vasoconstriction
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4
Q

describe the dose responses to intravenous epinephrine

A
  • 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

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5
Q

describe the Vascular effects of epinephrine

A
  • 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

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6
Q

Describe the epinephrine reversal phenomenon

A
  • alpha receptor antagonism causes INCREASE epinephrine induced VASODILATION –> DECREASE TPR –> DECREASE MAP
  • Beta receptor antagonism –> Ephinephrine induced vasoconstriction unmasked –> INCREASE MAP
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7
Q

describe the cardiac effects of epinephrine

A
  • 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
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8
Q

describe the toxicity and adverse effects of epinephrine

A
  • 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)

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9
Q

what are the therapeutic uses of epinephrine

A
  • Hypersensitivity reactions, including anaphylaxis
  • cardiac arrest
  • ingredient in local anesthetics
  • post-extubation croup, viral croup
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10
Q

describe properties of Norepinephrine

A
  • equipotent to epinephrine in stimulating BETA 1 RECEPTORS
  • POTENT ALPHA AGONIST (mroe so than epinephrine)
  • LITTLE ACTION ON BETA 2 RECEPTORS
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11
Q

describe the effects of norepinephrine

A
  • 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
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12
Q

describe the toxicity/adverse effects of norepinephrine

A
  • same as epinephrine

–> restlessness, headache, tremor, palpitations

–> cerebral hemorrahge

–> cardiac arrhythmias

  • angina in patients with coronary artery disease
  • GREATER ELEVATION OF BLOOD PRESSURE
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13
Q

DOPAMINE

A

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
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14
Q

Describe Dose response of DOPAMINE

A
  • 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)

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15
Q

Adverse reaction/ precautions of DOPAMINE

A
  • 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

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16
Q

USE of DOPAMINE

A

USED TO TREAT:

–> Severe congestive heart failure, particularly in patients with oliguria and low or normal peripheral vascular resitsance

–> cardiogenic and septic shock

–> may acutely improve cardiac and renal function in severely ill patietns with chronic heart disease or renal failure

17
Q

What are the effects of treating with reserpine or guanethidine prior to giving direct acting adrenergic agonists

A
  • RESPONES OF DIRECT ACTING ADRENERGIC AGONISTS are NOT REDUCED BY PRIOR TX WITH RESERPINE OR GUANETHIDINE
  • response may be potentiated by cocaine, reserpine and guanethidine