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03 BP1 > 08 Cholinergics > Flashcards

08 Cholinergics Flashcards

1
Q

Muscarinic receptors

A 
M1 = CNS, salivary glands, stomach parietal cells
M2 = heart, some smooth muscles, nerve
M3 = smooth muscles, skin, exocrine glands secretion, vasodilation
M1/2/3 = IP3 and DAG
M2/4 = inhibition of CAMP, activation of K channels (repolarization -> bradycardia, dec force of contraction and rate of AV conduction -> dec CO)
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2
Q

Nicotinic receptors

A 
Nm = NMJ
Nn = autonomic ganglia, CNS, adrenal medulla
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3
Q

Choline esters

A

Ach, methacholine, carbachol, bethanecol
Hydrophilic (poorly absorbed in CNS)

Ach, Carbachol = both receptors
Methacholine = more muscarinic
Bethanecol = only muscarinic

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4
Q

Alkaloids

A

Muscarine (toxic, less absorbed), pilocarpine = muscarinic (MuPasa)
Nicotine (easily absorbed), lobeline = nicotinic (NaLa)

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5
Q

Muscarinic receptor activator

A

M1/3/5 (Gq): IP3 and DAG; increase in Ca+ -> smooth muscle contractions except heart; increase in cGMP -> increase in K in cardiac cell
M2 (Gi), M4 (Gq): inhibit adenelyl cyclase -> decrease CAMP; activate K channel -> repolarization -> bradycardia

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6
Q

Nicotinic receptor activator

A

Opens Na and K channels -> depolarization of nerve/NMJ -> muscle contraction

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7
Q

Cholinomimetics

A

Direct acting = alkaloids (muscarine, nicotine, pilocarpine, lobeline) and choline esters (ach, methacholine, carbachol, bethanecol)
Indirect acting = simple alcohols (edrophonium), carbamates (neostigmine, pyridostigmine, physostigmine), organophosphates (ethothiophate, malathoin, parathion)

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8
Q

Simple alcohols

A

Quaternary ammonium group (edrophonium)

H-bond (weak), 5 minutes

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9
Q

Carbamic acid/carbamates

A

Quaternary/tertiary ammonium group, polar = poor absorption
Covalent bond, longer, reversible
Neostigmine
Pyridostigmine
Physostigmine: well absorbed, eye, exception = lipophilic = cross BBB, more toxic
Carbaryl: very lipid soluble

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10
Q

Organophosphates

A

Very lipid soluble = good absorption until BBB = toxic
Parathion and malathion: must be activated in body buy conversion to O2 analogs
Echothiophate: exception = hydrophilic, more stable

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11
Q

Group 1

A

Reversible cholinesterase inhibitor
Reversible bind electrostatically via H-bond
Short lived (2-10 min)
ex. Edrophonium

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12
Q

Group 2

A

Reversible cholinesterase inhibitor
Two-step hydrolysis sequence like Ach -> covalent bond is not hydrated
Long course (30 min- 6h)
ex. Carbamates

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13
Q

Group 3

A

Irreversible cholinesterase inhibitor
Covalent bond is stable
Binding-hydrolysis -> aging (breaking of O2-P groups of inhibitor) -> stronger P-enzyme bond
Pralidoxime: breaks P-enzyme bonds BEFORE AGING
Atropine: anti-cholinergic (reverse initial effects of organophosphates)

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14
Q

Clinical effects on the eye

A

Glaucoma: closed angle = increase intraocular pressure
Cholinomimetics: contraction of ciliary body + decreased secretion -> aqueous outflow -> dec intraocular pressure

Acute angle-closure glaucoma -> direct muscarinic agonist + another drug -> surgery

Esotropia in young children (cross eyed): cholinomimetics to help accommodation

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15
Q

Clinical effects on respi

A

Nonspecific bronchoprovocation test (asthma): methacholine

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16
Q

Clinical effects on GIT

A

Increases smooth muscle activity (post-operative ileus, congenital megacolon): bethanecol
Increase salivary secretion: pilocarpine,
Sjorgen syndrome: Cevimeline

17
Q

Clinical effects on urinary tract

A

Cause contraction of the detrusor muscle: bethanecol (DOC), neostigmine

18
Q

Clinical effects on NMJ

A 
Myasthenia gravis (autoimmune disease that attacks NMJ = decreased contraction): Neostigmine (every 4h), pyridostigmine (every 6h); immunosuppressants; Ig and plasmapheresis
Tensilon test: edrophonium = improved muscle strength

Respiratory arrest: intranasal neostigmine

Neuromuscular blockade: IV/IM neostigmine and edrophonium

19
Q

Clinical effects on heart

A

Supraventricular tachyarrhythmias: edrophonium, adenosine, verapamil, diltiazem

20
Q

Clinical effects on antimuscarinic drug intoxication

A

Atropine intoxication and TCA overdose: physostigmine (emergency), neostigmine, pyridostigmine

21
Q

Clinical effects on CNS

A

Alzheimer’s (dec ach): Tacrine (direct and indirect), donepezil, galantamine, rivastigmin

22
Q

Signs of muscarinic excess

A 
Salivation
Lacrimation
Urination
Defecation
GI cramping
Emesis
23
Q

Signs of nicotinic excess

A 
Muscle cramps
Twitching
Weakness
Tachycardia and hypertension
Fasciculations
24
Q

Varenicline

A

Nicotinic partial agonist

Prevents stimulant effect of nicotine that causes dopamine release

25
Q

Organophosphate poisoning symptoms

A 
Diarrhea
Urination
Miosis
Bronchospasms
Bradycardia (dec HR)
Excitation of skeletal m. and CNS
Lacrimation
Salivation
Sweating 
vomiting  --> Atropine and pralidoxime

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