Norepinephrine has minimal effects on airway resistance, why?
-Bronchial smooth muscle are mostly Beta 2, NorEpi does not stimulate Beta 2
What 2 sympathomemetics have strong Beta 2 activation and therefore are potent bronchodilators?
- Epinepherine
- Isoproterenol
All drugs containing the 3,4 dihydroxybenzene (catecholamines) structure are rapidly inactivated by what 2 enzymes.
- MAO (Liver, kidney, GI)
- COMT
Inhibition of what mechanism produces a greater potentiation of epinepherine than inhibition of enzymes. and is evidenced by what?
- Reuptake
- Minimal presence of chatecholamines in urine
Why are synthetic non-catecholamines slower to degrade then other catecholamines?
-They are not metabolized by COMT
Patients on an MAOI may have and exaggerated response to what type of catecholamine?
synthetic non-catecholamines
How does ephedrine work?
- Has direct and indirect action primarily through release of NorEpi
- Works on Alpha 1 and Beta receptors
What is ephedrine’s principle mechanism of action?
-Increased myocardial contractility
How does ephedrine increase mycardial contractility?
-Greater venoconstriction than arterial constriction leads to increased preload, paired w/ increased HR increases CO
3 Other ephedrine tidbits.
- Tachyphylaxis can occur
- Preserves uterine blood flow
- Bronchial smooth muscle relaxor
What is the onset and duration of ephedrine and Phenylepherine?
- Onset = 1 min
- Duration = 5-10 minutes
How does phenylepherine work?
- Synthetic non-catecholamine
- Venoconstriction greater than arterial constriction (increased preload)
- Increase PVR
What drug May be used to improve coronary perfusion pressure without chronotropic side effects.
Phenylepherine
What 3 problems are seen with Phenylepherine?
- Reflex bradycardia
- Decreased renal and splanchnic blood flow
- Increase pulmonary artery resistance
What drug can reverse the R to L shunt associated with tetrology of fallot
Phenylepherine
Phenylepherine is like ____________ but less potent and longer lasting.
-NorEpi
Ephedrine is like __________ but BP response is less intense and last longer
Epinepherine
What is NorEpi? And what does it do?
- Endogenous neurotransmitter responsible for maintaining BP by adjusting SVR
- primarily Acts on Alpha 1
NorEpi is a potent vasconstrictor of what? and what does this lead to?
- Renal (oliguria)
- Mesenteric (Mesenteric infarct)
- Cutaneous (Gangrene of digits)
NorEpi primarily works on what receptor?
-Alpha 1
How does NorEpi effect CO?
- Increase at low doses
- Decrease at high doses
How do you titrate NorEpi?
-To flow no BP (By blood gas base deficit)
What is epinepherine? and what receptors does it work on?
- Prototypical catecholamine
- Alpha 1, Beta 1, Beta 2
What is the most potent activator of Alpha 1 receptors?
-Epinepherine
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