Adrenergics - Indirect Acting Agonists Flashcards
What is an indirect acting adrenergic agonist?
releases endogenous NE from nerve terminals
What is tyramine’s only mechanism of action?
Indirect release of NE (ONLY INDIRECT)
Where is Tyramine found?
In foods, not a drug
What types of foods contain high levels of tyramine?
Fermented foods -> wine, beer, some cheeses and sausages
Without any drug interactions, what normally happens to tyramine?
Degraded in liver by MAO (rapidly) and tyramine never enters system/has a negative impact
What happens (clinically) if tyramine acts?
HTN (crisis) b/c too much release of NE
Why can tyramine be an issue with some drugs?
Drugs that block MAO, will lead to increase in Tyramine in system -> HTN crisis
What are the mechanisms of action of amphetamine? (broadly)
Direct and indirect action -> increase NE release and stimulate adrenergic receptors
What are the mechanisms of action of amphetamine (specifically)?
Release NE from adrenergic neurons
Weakly stimulate A and B receptors
Inhibits NET -> important b/c it competes with NE for uptake back into cell leaving more NE in synaptic cleft
Where does amphetamine act?
CNS (a lot), weaker direct actions in PNS
What are the therapeutic uses of amphetamine?
narcolepsy, ADD (paradoxal effect in kids)
What is the route of administration of amphetamine?
Oral
What is the relative half life of amphetamine?
Long (several hours)
How does amphetamine increase presence of NE?
Competes for uptake into storage granules, so increased NE in cytoplasm of cell -> a carrier moves it out into synaptic cleft. This system overrides the MAO pathway too
What is the mechanism of action of ephedrine?
Direct - A and B agonist
Indirect - releases NE to activate adrenergic receptors
What is the main effect of an indirect agonist (general)?
Cause increase release of NE, so going to do all the things NE does. Increase BP and TVR, but no change in HR
How is ephedrine administered?
Orally
Where does ephedrine act? (CNS or PNS)
CNS
What is clinically significant about ephedrine?
Was found in many herbal concoctions with unknown consumption of high amounts -> importance of knowing what herbal supplements a pt is on
What is the mechanism of action of pseudoephedrine?
Direct - A1 activity with little B2 agonist activity
What is the route of administration of pseudoephedrine?
orally
What is the major therapeutic use of pseudoephedrine?
Nasal decongestant - b/c of A1 agonist effects
What are the side effects of all A agonists and why? (3)
Throbbing headaches due to potent vasoconstriction
cerebral hemmorhage - b/c increased systemic blood pressure
Restlessness and anxiety
What are the side effects of all B agonists and why?
Increased heart rate (palpatations)
Cardiac arrhythmias (b/c increase HR)
Pericardial pain (angina) b/c of increased HR ->especially in pts with CAD
restlessness and anxiety
