Cholinomimetics Flashcards
Recall the 2 types of directly acting cholinomimetics and give an example of each
- Choline esters (bethanechol)
2. Alkaloids (Pilocarpine)
Recall the selectivity of 2 example directly-acting cholinomimetics
- Bethanechol - M3 selectivity
2. Pilocarpine - non-selective muscarinic selectivity
Recall the side effects common to all cholinomimetics
Sweating Impaired vision Bradycardia Hypotension Respiratory difficulty
Recall the main clinical use of 2 directly-acting cholinomimetic drugs
Bethanechol - bladder emptying and GIT motility
Pilocarpine - glaucoma
Why is pilocarpine suitable as a glaucoma treatment?
High lipid solubility so can be applied locally
Opens up drainage angle into canals of Schlemm by excitation of ciliary muscles
What sort of drugs are classed as indirectly-acting cholinomimetics?
ACh esterase inhibitors
Recall the 2 types of cholineesterase and their distribution in tissue
- ACh esterase - all cholinergic synapses
2. butyrylcholinesterases - plasma and most tissues
Recall the effect of cholineesterase inhibitors at mild and high doses
Mild dose - muscarinic excitation
High dose - depolarising block
Compare the substrate specifity and speed of ACh esterases and butyrylesterases
AChE - very specific for ACh, very rapid
BChE - broad specificity *=(also hydrolyses suxamethonium), slightly slower
Give an example of a reversible and an irreversible cholinesterase inhibitor
Reversible - physostigmine
Irreversible - ecothiopate
Give 2 clinical uses for physostigmine
Glaucoma + atropine poisoning
Recall the mechanism of action of physostigmine
Donates a carbamyl group to a serine in the active site of AChE, blocking the active site
Recall the mechanism of action of ecothiopate
Irreversibly phosphorylates the active site to block it
What sort of compounds are irreversible cholineesterase inhibitors?
Organophosphates
Recall a clinical use of ecothiopate
Glaucoma treatment
