Cholinergic Agonists

Question 1

How is action of ACh terminated?

Answer 1

Degradation by acetylcholinesterase

Question 2

Where is acetylcholinesterase localized?

Answer 2

Pre and post-synaptic membranes of synaptic cleft

Question 3

What are the two types of cholinergic receptors?

Answer 3

Muscarinic and nicotinic

Question 4

What are the two types of nicotinic receptors?

Answer 4

Nm = neuromuscular
Nn = neuronal

Question 5

What are muscarinic effects of ACh on following: 
1. Heart rate
2. Eye
3. Respiration
4 GI
5. Bladder
6. Glands

Answer 5

1. Decrease
2. Miosis - pupil constriction
3. Bronchoconstriction, increase secretions
4. Increase motility, relax sphincters, nausea, vomiting, diarrhea, cramps
5. Relax sphincter, contract wall
6. Increase secretions

Question 6

What are nicotinic effects of ACh on following:

1. Neuromuscular junction
2. Ganglia
3. Adrenal medulla

Answer 6

1. Muscle contraction, fasciculations, tremors
2. Activate PNS & SNS
3. Release epinephrine

Question 7

Bethanechol and Carbachol

How do you take it:
Treats:
Mechanism:

Answer 7

Oral/SC/topical - 1 hr duration

Cholinergic agonist - muscarinic receptors

Treats: urinary retention and xerostomia - dry mouth

Question 8

Pilocarpine

Answer 8

Cholinergic agonist

Topical - 24 hr

Treats: Acute glaucoma - decreases intraocular pressure by inducing miosis by contracting ciliary muscles

Question 9

How is ACh used clinically?

Answer 9

It’s not (b/c only has a 2 min duration)

Question 10

What are general adverse effects of cholinergic drugs?

Answer 10

DUMB BELSS

Diarrhea, urination, miosis, bronchoconstriction, bradycardia, excitation (of skeletal muscle and CNS), lacrimation, salivation, sweating

Question 11

Edrophonium

Answer 11

Reversible acetylcholine esterase inhibitor

Test for myasthenia gravis - short half life

Question 12

Myasthenia gravis

Answer 12

Reduced muscle contraction due to blockage of receptors by antibodies (auto-immune)

Question 13

Donepezil (Aricept)

Answer 13

Reversible AChEsterase inhibitor that can enter the CNS

Alzheimer’s

Question 14

Echothiophate (Phospholine) and Isoflurophate

Answer 14

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

Question 15

Sarin, organophosphates

Answer 15

Irreversible ACh esterase inhibitors

Used as insecticides, nerve gas

Question 16

What are two drugs used as antidotes for irreversible ACh esterase inhibitors? (For example if someone is poisoned with nerve gas)

Answer 16

Atropine - peripheral muscarinic sites

PAM (pralidoxime) - nicotinic sites

Question 17

Neostigmine (stigmine) (Prostigmin) and Pyridostigmine (stigmine) (Mestinon)

Answer 17

Reversible Acetylcholine Esterase inhibitor - act on nicotinic receptors at NMJ’s

Myasthenia gravis, open-angle glaucoma, reversal of nondepolarizing neuromuscular blockade after surgery

Question 18

Physostigmine (**stigmine) (Antilirium)

Answer 18

Reversible ACh esterase inhibitor that can enter CNS

treats overdose of atropine

Question 19

Methacholine

Answer 19

Cholinergic agonist

Used to test asthma