Page 45 - pharma 1 theoretical updated MNU_Neat

Clinical pharmacy 2024/2025 Level 3 Pharm D Pharmacology 1 (PO 502)

Muscarinic agonists "Cholinergic drugs"

Direct acting Indirect acting
 Choline esters ➔ Cholinesterase inhibitors or anticholinesterase.

methacholine, bethanechol, • Reversible anticholinesterase ➔
carbachol physostigmine, neostigmine, edrophonium &
 Naturally occurring alkaloids pyridostigmine.

➔ muscarine, pilocarpine. • Irreversible anticholinesterase ➔
organophosphorus compounds → insecticides

& war gases.

1- Direct acting drugs

➢ Choline esters

a) Methacholine

➢ Substitution of methyl group on β-carbon Uses:
of Ach. 1. Atrial tachycardia.

 Weak nicotinic activity. 2. Acute urinary retention, post-
 Resistant to hydrolysis by operative retention of urine ➔ due to
pseudocholinesterase ➔ rate of hydrolysis contraction of bladder muscle ➔
is slower than Ach. expulsion of urine.

 So, methacholine is almost purely 3. in post-operative abdominal
muscarinic with long duration of action. distention or intestinal atony.
 Can be given orally & by injection, but 4. Glaucoma ➔ 20% with neostigmine

this drug is never injected IV, because it 5% is recommended for emergency
can produce great cardiac slowing & treatment of acute attack.
hypotension 5. Diagnosis of pheochromocytoma

S/E: ➔ 15 mg SC →  BP rather than
Sweating, salivation, lacrimation, intestinal decrease due to massive release of
pain, cramps, diarrhea, flushing, difficult NE from the tumor.

breathing & hypotension.  Atropine should be available as
C/I: antidote.
Bronchial asthma, coronary diseases,

mechanical obstruction of GIT & bladder & in
peptic ulcer.

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