Cholinomimetics and Muscarinic Antagonists Flashcards
Bretylium and Guanethidine MOA
Blocks the release of norepinephrine from the nerve terminals
Reserpine MOA
blocks neurotransmitter packaging into vesicles, thus lowering functional transmitter release (e.g., of NE) into the synapse
Amphetamine, ephedrine MOA
augment the release of the patient’s norepinephrine from the nerve terminals
Metyrosine MOA
Inhibits the conversion of tyrosine to DOPA, which consequently reduces the levels of dopamine and norepinephrine in the body.
Vesamicol MOA
Prevents the uptake of ACh into presynaptic vesicles, decreasing ACh activity
Hemicholinium MOA
Reduces the synthesis and level of ACh by blocking the uptake of choline, a building block of ACh, into presynaptic neurons
Name four direct cholinergic agonists.
Bethanechol, carbachol, pilocarpine, and methacholine
Bethanechol uses?
Postoperative and neurogenic ileus, urinary retention (Bethany, call [bethanechol] me if you want to activate your bowels and bladder)
In a patient with glaucoma, what are two direct agonist cholinomimetic drugs that can be prescribed?
Carbachol (carbon copy of acetylcholine) and pilocarpine
actions on ciliary muscle and pupillary sphincter (M3)
You suspect that your patient has asthma and plan to perform a challenge test. What is the agent of choice, and how does it work?
Methacholine—when inhaled, it stimulates muscarinic receptors in the airways and induces bronchoconstriction
7 indirect cholindergic agonists
Neostigmine, pyridostigmine, edrophonium, physostigmine, donepezil, rivastigmine, & galantamine
Neostigmine uses?
Postoperative and neurogenic ileus and urinary retention, myasthenia gravis, reversal of neuromuscular junction blockade (postoperative)
In a patient with signs of myasthenia gravis, which anticholinesterase can you use to confirm your diagnosis? Why?
Edrophonium; the effects last for minutes, and if weakness is transiently reversed, it is diagnostic of myasthenia gravis
You accidentally overdose a patient with atropine. What pharmacologic agent should you use to fix your mistake? Why?
Physostigmine; it can cross the blood-brain barrier and reverse central and peripheral nervous system effects (phyxes atropine overdose)
Why is pyridostigmine used to treat myasthenia gravis?
Increases endogenous acetylcholine and muscle strength and is long acting and does not penetrate the CNS
A patient has Alzheimer disease. What cholinomimetic agents can be prescribed for his treatment?
Donepezil, rivastigmine, galantamine
You administer an anticholinesterase to an Alzheimer’s patient. What are some conditions that could be exacerbated by this class of agent?
COPD, peptic ulcers, and asthma
Antidote to organophosphates
Atropine (competitive inhibitor) + pralidoxime (regenerates AChE)
An elderly patient takes benztropine but cannot remember why. What is the likely clinical application and mechanism of action?
Benztropine, a muscarinic antagonist, is used to ease cholinergic symptoms of Parkinson disease (park my Benz) and to treat acute dystonia
A patient’s severe asthma attack is unresponsive to albuterol. What other medications that act as muscarinic antagonists can be used?
Ipratropium and tiotropium are muscarinic antagonists used to treat asthma and COPD (I pray I can breathe soon)
What is the mechanism and clinical application for oxybutynin, solifenacin, and tolterodine?
Muscarinic antagonists used to ease bladder spasms and relieve urge urinary incontinence (overactive bladder)
A patient is administered glycopyrrolate parenterally before surgery. What is the effect of this agent? What if it’s given orally?
Muscarinic antagonist used to reduce airway secretions. If given orally, to treat peptic ulcers.
A patient complains of motion sickness. What muscarinic antagonist is most commonly used for treatment?
Scopolamine
CNS penetration
A patient is found to have irritable bowel syndrome. Which muscarinic antagonists can be prescribed as antispasmodics for this patient?
Hyoscyamine, dicyclomine
Jimson weed (Datura)
gardener’s pupil (mydriasis due to plant alkaloids)
Don’t get confused with organophosphates
