Martin - Adrenergic Agonists/Antagonists Flashcards
What is the primary NT released from presynaptic neurons in the sympathetic ganglia? What receptor type does it act on?
ACh released from presynaptic neurons in sympathetic chain ganglia.
Acts on nicotinic receptors
What is the primary sympathetic NT released from postsynpatic neurons onto cardiac and smooth mm cells?
Norepinephrine
What is the major effect of dopamine in the periphery? Through which receptors does it achieve this effect?
Dilates renal afferent blood vessels via activation of D1 receptors, thus increasing renal blood flow
What is the effect of norepinephrine on peripheral vascular resistance? Through what receptors does it elicit this effect?
Increased peripheral resistance via stimulation of α1 receptors
What is the effect of increased peripheral resistance caused by norepinephrine?
Decreased heart rate due to increased baroreceptor reflex activity
What effect does low dose epinephrine have on peripheral resistance?
Low dose epi will mildly decrease peripheral resistance
What type of drug is Isoproterenol?
Pure β agonist
What effect will isoproterenol have on peripheral resistance?
Isoproterenol will cause a major decrease in peripheral resistance
What effect will isoproterenol have on heart rate?
Reflex tachycarda due to decrease in peripheral resistance and drop in MAP
What is the difference between low dose and high dose epinephrine?
At low doses, epi will cause decreased peripheral resistance via β2 receptors, but at high doses it will cause a marked increase in peripheral resistance due to higher affinity α1 stimulation
What type of drug is phenylephrine?
α1-adrenergic agonist, also know as a pressor agent
What does the term “mixed acting α agonist” imply?
The drug (i.e. Metaraminol) will directly stimulate α1 receptors, but will also stimulate norepinephrine release
What are the effects of phenylephrine?
Vasoconstriction leading to increased peripheral resistance and overall BP, which can cause reflex bradycardia
What agent can be used to block the reflex bradycarda caused by phenylephrine?
Atropine
What is phenylephrine used for?
Maintain BP in hypotensive states such as spinal anesthesia
Induce the baroreceptor reflex and slowing of the heart in conditions like paroxysmal atrial tachycardia
Nasal decongestant
What are the vascular effects of dopamine? Through what receptor are these effects achieved?
Vasodilation of renal, coronary, and mesenteric vascular beds via stimulation of D1 receptors. Main goal is to increase renal blood flow.
What caution must be taken when administering dopamine?
BP must be monitored because it will cause α1-mediated vasoconstriction at high concentrations, resulting in end-organ ischemia
What is the order of peripheral receptor activation by increasing concentrations of dopamine?
D1 > β1 > α1
What is dopamine used for?
Increases cardiac output and renal blood flow in cases of shock or CHF
What kind of drug is Dobutamine?
β1-selective agonist with some α1 agonist/antagonist effects
Mostly has β1 effects
What are the effects of Dobutamine?
Increased inotropy and some increase in heart rate
Increased cardiac output
Little vascular effect
ONLY USED SHORT TERM
What are potential adverse effects of Dobutamine?
May increase size of infarct
May cause potential arrhythmias
Increases the work/O2 requirement
What is the primary use of α1-selective antagonists?
2nd or 3rd line treatment for essential HTN
Usually used in combination with other agents from different drug classes
What are the main effects of α1-selective antagonists?
Decreased peripheral vascular resistance, venous return, and preload
Usually do not increase HR or CO
No α2 blockade so no increased release of norepi
Lipids: Decreases LDL and TGL, increases HDL