Cholinergic Agonists Flashcards
How is action of ACh terminated?
Degradation by acetylcholinesterase
Where is acetylcholinesterase localized?
Pre and post-synaptic membranes of synaptic cleft
What are the two types of cholinergic receptors?
Muscarinic and nicotinic
What are the two types of nicotinic receptors?
Nm = neuromuscular Nn = neuronal
What are muscarinic effects of ACh on following: 1. Heart rate 2. Eye 3. Respiration 4 GI 5. Bladder 6. Glands
- Decrease
- Miosis - pupil constriction
- Bronchoconstriction, increase secretions
- Increase motility, relax sphincters, nausea, vomiting, diarrhea, cramps
- Relax sphincter, contract wall
- Increase secretions
What are nicotinic effects of ACh on following:
- Neuromuscular junction
- Ganglia
- Adrenal medulla
- Muscle contraction, fasciculations, tremors
- Activate PNS & SNS
- Release epinephrine
Bethanechol and Carbachol
How do you take it:
Treats:
Mechanism:
Oral/SC/topical - 1 hr duration
Cholinergic agonist - muscarinic receptors
Treats: urinary retention and xerostomia - dry mouth
Pilocarpine
Cholinergic agonist
Topical - 24 hr
Treats: Acute glaucoma - decreases intraocular pressure by inducing miosis by contracting ciliary muscles
How is ACh used clinically?
It’s not (b/c only has a 2 min duration)
What are general adverse effects of cholinergic drugs?
DUMB BELSS
Diarrhea, urination, miosis, bronchoconstriction, bradycardia, excitation (of skeletal muscle and CNS), lacrimation, salivation, sweating
Edrophonium
Reversible acetylcholine esterase inhibitor
Test for myasthenia gravis - short half life
Myasthenia gravis
Reduced muscle contraction due to blockage of receptors by antibodies (auto-immune)
Donepezil (Aricept)
Reversible AChEsterase inhibitor that can enter the CNS
Alzheimer’s
Echothiophate (Phospholine) and Isoflurophate
Irreversible inhibitor of acetylcholine esterase
Mechanism: Phosphorylate the esterase and inhibit it, raising [ACh], causing contraction of ciliary body/muscles so that more drainage of aqueous humor occurs
Eye topicals
Treats: Chronic glaucoma
Sarin, organophosphates
Irreversible ACh esterase inhibitors
Used as insecticides, nerve gas
What are two drugs used as antidotes for irreversible ACh esterase inhibitors? (For example if someone is poisoned with nerve gas)
Atropine - peripheral muscarinic sites
PAM (pralidoxime) - nicotinic sites
Neostigmine (stigmine) (Prostigmin) and Pyridostigmine (stigmine) (Mestinon)
Reversible Acetylcholine Esterase inhibitor - act on nicotinic receptors at NMJ’s
Myasthenia gravis, open-angle glaucoma, reversal of nondepolarizing neuromuscular blockade after surgery
Physostigmine (**stigmine) (Antilirium)
Reversible ACh esterase inhibitor that can enter CNS
treats overdose of atropine
Methacholine
Cholinergic agonist
Used to test asthma
