Cholinomimetics Flashcards
What are cholinomimetics
Medication that mimic acetylcholine
List examples of cholinomimetics
Pilocarpine
Bethanecol
Carbachol
Methacholine
Explain the mode of action of Bethanechol
Bethanechol acts only on Muscarinic receptors
It is given to people with ileus to stimulate motility in the intestine, or to stimulate bladder contractility in people with urinary retention. Most commonly these are side effects of general anesthetic given to people in surgery
Explain the mode of action of Pilocarpine and carbachol
Pilocarpine acts only on Muscarinic receptors and is used to treat glaucoma. It causes ciliary muscles to contract when added directly to the eye and this increases the outflow of aqueous humor, the fluid in the anterior chamber of the eye, resulting in reduced pressure
Carbachol acts on both nicotinic and muscarinic receotors but is used less frequently as it is more potent and could lead to stronger side effects
Explain another use for pilocarpine
It is used to stimulate tear glands and salivary glands in people with sjogren syndrome, a disease where the persons own immune system destroys these glands
It can also be used to stimulate sweat glands to test for cystic fibrosis in children.
What does methacholine do?
Methacholine acts primarily on muscarinic receptors and is used as a screening tool for asthma. It causes the bronchiole smooth muscles to contract when inhaled and in people with asthma, it will lead to worse symptoms because of their hyperactive bronchiole smooth muscle.
What do anticholinesterases do?
They inhibit cholinesterase which degrade acteylcholines and leads to prolonged acetyl choline mediated effects on muscarinic and nicotinic receptors
List some examples of anticholinersterases
edrophonium, neostigmine, physostigmine, pyridostigmine, rivastigmine, galantamine, and donepezil.
How many types of anticholinesterases are there? name them
There are 2 types, Organophosphates and Carbamates
What are carbamates
These are anticholinesterases which are either tertiary or quartenary amines. Only the tertiary amines can cross the blood brain barrier
What are Edrophonium and Pyridostigmine used for
Edrophonium and Pyridostigmine are quarternary amines. Edrophonium is used to test for myasthenia gravis because it is the shortest acting. It increases the concentration of acetylcholine so it can bind to the nicotinic receptors on muscles cells preventing antibodies from binding
Pyridostigmine is the longest acting so it is used to treat myasthenia gravis
What is neostigmine used for?
Neostigmine is used to reverse effects of neuromuscular blockers used on patients during surgery. It increases the concentration of acetylcholine and displaces the neuromuscular blockers on nicotinic receptors to reverse the paralysis
What are Donepezil, Rivastigmine and galantamine used for and why?
They are used to to increase levels of acetylcholine in patients with Alzheimers at the Basal nucleus of meynert. They are used because they can cross the blood brain barrier
What is physostigmine used for?
Physostigmine is used as an antidote for overdose of an anti-cholinergic, such as atropine.
because if someone takes too much atropine, they’ll develop peripheral effects, such as constipation and urinary retention, as well as central nervous system effects, such confusion or tremors.
