Indirect acting cholinergic agonists

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Actions of an Indirect cholinergic agonist?

1. inhibit ACHE, thus increasing ACH in synapse at all locations where ACH is released
2. stimulate Muscarinic receptors on autonomic organs
3. stimulate then desensitize ganglia and skeletal muscle

Reversible indirect cholinergic agonists include?

1. carbamates,
2. Quaternary ammoniums
reverse in minutes to hours

Irreversible indirect cholinergic agonists include?

1. Nerve gas
2. organophosphates

Tx uses for indirect cholinergic agonists

1. paralytic ileus-->stimulate urinary bladder
2. glaucoma
3. myasthenia gravis
4. anticholinergic poisoning
5. alzheimer's disease
6. reversal of neruomuscular blockade
7.prophylaxsis of cholinesterase poisoning

physostigmine tx dosage form?

orally active but only available as injection
crosses BBB

physostigmine tx uses and side effects

1. mitotic in glaucoma
2. atropine toxicity
SE
1.muscarinic: SLUD

neostigmine dosage form

-P.O and injection
-doesnt cross bbb(no cns actions
only use for peripheral effects

neostigmine tx uses

1. paralytic ileus
2.urinary retention
3. myasthenia gravis-short t1/2 so needs multiple doses
4. reverse neuromuscular blockade

Pyridostigmine dosage form

-P.O/ injection
-slower onset
-longer dura of action

pyridostigmine tx. uses

1. myasthenia gravis
2. prophylactic for nerve gases-only inhibit 20-30% enzyme activity so protecting ACHE
3. reverse neuromuscular blockade

Ambenonium dosage form

P.O
-longer DOA than neostigmine
fewer side effects

ambenonium tx. uses

1. myasthenia gravis
2. some muscle activation***Partial agonist activation
3. Narrow therapeutic index

Edrophonium DF and TX uses

1. Injection--short DOA(10mins)
--lacks carbamoyl group, blocks anionic site
2.diagnosis of Myasthenia gravis

Tacrine place of action

1. CNS selective-no carbamoyl, reversible inhibitor

Tacrine TX uses

1. Alzheimers disease (15-30% patients)
does not slow disease
need to be give QID
hepatotoxicity limits its use but it is reversible so DC

Donepezil Tx. indications

1. Alzheimers disease
--QD, no hepatotoxicity
--Effective in 80% patients
--may slightly slow disease (55wks) but not alter
2. Muscarinic SE (SLUD)

Galantamine TX use and Side effects

1. Alzheimers disease
-PO BID
2. SE: liver, GI tract, Bronchoconstriction, drowsiness
**less effective than aricept(donepezil)
**reversible inhibitor (ACHE)

Rivastigmine TX uses and Side effects

1. Alzheimers (newest agent)
-P.O bid (DOA: 10hrs)
-may slow progression
--selective for G1 isoform mostly in brain, slowly dissociates
2. Muscarinic(SLUD) hallucinations

These structural features help organophosphates have good cns penetration?

1. high lipid solubility
2. low molecular weight
3. transdermal absorption

Prophylaxis treatment of organophosphates

1. pyridostigmine-->reversible indirect agonist (will bind to ACHE reversibly)

Treatment of organophosphate poisoning

1. Atropine-antagonist at muscarinic receptors
2. Pralidoxime(2PAM)
-chem. rxn w/ organophosphate bound to ACHE

Example of Organophosphates

1. Tabun
2. Sarin
3. soman
4. Paration
5. Diazinon, dimpylate
6. malathion

once this process occurs 2PAM is no longer able to bind with the organophosphate and reverse the binding

AGING

EFFECTS of organophosphate/nerve gas treatment

SLUD (at muscarinic effects)
diaphragm contraction-->muscle contraction so can't breathe (DIE)

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