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Pharmacology > 01 Cholinergic pharmacology > Flashcards

01 Cholinergic pharmacology Flashcards

1
Q

1.01 MUSCARINICS - EYE

Pilocarpine, cevimeline - actions

A

muscarinic receptor agonists
parasympathomimetic actions: contract smooth muscle (e.g. gut, bladder, pupil); decrease rate and force of heart beat; increase secretions (e.g. salivary, sweat, gastric acid); inhibit neurotransmitter release

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2
Q

1.01 MUSCARINICS - EYE

Pilocarpine, cevimeline - MOA

A

action in glaucoma is due to interaction with M3 receptors which couple to Gq to increase cellular IP3 and DAG concentrations
constriction of pupil aids drainage of aqueous humour and lowers intraocular pressure

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3
Q

1.01 MUSCARINICS - EYE

Pilocarpine, cevimeline - abs/distrib/elim

A

for glaucoma, pilocarpine is given as eye drops and actions last for a day
a slow delivery system placed under the eyelid acts for several days
pilocarpine and cevimeline tablets are taken 3 times daily in patients with dry mouth

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4
Q

1.01 MUSCARINICS - EYE

Pilocarpine, cevimeline - clinical use

A

glaucoma (narrow and wide angle)
dry mouth due to poor salivary gland function (e.g. Sjogren’s syndrome)

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5
Q

1.01 MUSCARINICS - EYE

Pilocarpine, cevimeline - adverse effects

A

blurred vision (contraction of ciliary muscle)
topically applied formulations have limited systemic absorption and few adverse effects, whereas the oral formulations can increase gastrointestinal activity and sweating

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6
Q

1.02 ANTIMUSCARINICS - EYE

Atropine, tropicamide, cyclopentolate - actions

A

muscarinic receptor antagonists
relax smooth muscle of the iris and ciliary body (causing pupillary dilation and paralysis of accommodation)

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7
Q

1.02 ANTIMUSCARINICS - EYE

Atropine, tropicamide, cyclopentolate - MOA

A

competitive reversible antagonism at all muscarinic receptors

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8
Q

1.02 ANTIMUSCARINICS - EYE

Atropine, tropicamide, cyclopentolate - abs/distrib/elim

A

topical preparations vary in their duration of action: tropicamide is short-acting (~6h), cyclopentolate up to 24h, and atropine up to 1 week

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9
Q

1.02 ANTIMUSCARINICS - EYE

Atropine, tropicamide, cyclopentolate - clinical use

A

paralysis of accommodation and pupil dilation for examination of the fundus of the eye (tropicamide)
relief of ciliary spasm in patients with anterior uveitis (atropine, cyclopentolate)

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10
Q

1.02 ANTIMUSCARINICS - EYE

Atropine, tropicamide, cyclopentolate - adverse effects

A

blurred vision
sensitivity to light due to pupillary dilatation
raised intraocular pressure

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11
Q

1.03 ANTIMUSCARINICS - GASTROINTESTINAL

Hyoscine, dicycloverine, atropine, glycopyrronium - actions

A

muscarinic receptor antagonists
relax smooth muscle (causing inhibition of peristalsis and reduction of spasm in gastrointestinal tract, etc.)
inhibit secretions (salivary, bronchial, sweat, gastric acid, etc.)
CNS actions: antiemetic, amnesic

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12
Q

1.03 ANTIMUSCARINICS - GASTROINTESTINAL

Hyoscine, dicycloverine, atropine, glycopyrronium - MOA

A

competitive reversible antagonism at all muscarinic receptors

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13
Q

1.03 ANTIMUSCARINICS - GASTROINTESTINAL

Hyoscine, dicycloverine, atropine, glycopyrronium - abs/distrib/elim

A

given orally
hyoscine can be administered as transdermal patch for effects lasting 2-3 days
hyoscine butylbromide does not enter the CNS and has mainly gut effects

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14
Q

1.03 ANTIMUSCARINICS - GASTROINTESTINAL

Hyoscine, dicycloverine, atropine, glycopyrronium - clinical use

A

hyoscine is mainly used in: motion sickness; reduction of salivary and gut secretions as an adjunct for anaesthesia
hyoscine butylbromide and dicycloverine: irritable bowel syndrome and gut spasms

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15
Q

1.03 ANTIMUSCARINICS - GASTROINTESTINAL

Hyoscine, dicycloverine, atropine, glycopyrronium - adverse effects

A

constipation
dry mouth
urinary retention
blurred vision
raised intraocular pressure
drowsiness

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16
Q

1.04 ANTIMUSCARINICS - BLADDER

Oxybutynin, tolterodine, trospium, solifenacin - actions

A

muscarinic receptor antagonists
antispasmodic effect on smooth muscle of bladder
inhibits bladder contraction and increases bladder volume

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17
Q

1.04 ANTIMUSCARINICS - BLADDER

Oxybutynin, tolterodine, trospium, solifenacin - MOA

A

competitive inhibition of muscarinic receptors - some of these agents are thought to be more selective for bladder muscarinic receptors and the M3 receptor

18
Q

1.04 ANTIMUSCARINICS - BLADDER

Oxybutynin, tolterodine, trospium, solifenacin - abs/distrib/elim

A

given orally
modified-release formulations are available for sustained effect

19
Q

1.04 ANTIMUSCARINICS - BLADDER

Oxybutynin, tolterodine, trospium, solifenacin - clinical use

A

urinary incontinence or urgency due to idiopathic overactive bladder or neurogenic bladder

20
Q

1.04 ANTIMUSCARINICS - BLADDER

Oxybutynin, tolterodine, trospium, solifenacin - adverse effects

A

dry eyes, dry mouth
abdominal discomfort

21
Q

1.05 NEUROMUSCULAR BLOCKER

Depolarising agent: succinylcholine (suxamethonium) - actions

A

nicotinic receptor agonist/depolarising neuromuscular blocker
short-lasting paralysis of skeletal muscle

22
Q

1.05 NEUROMUSCULAR BLOCKER

Depolarising agent: succinylcholine (suxamethonium) - MOA

A

action on nicotinic receptors produces a maintained depolarisation of the muscle membrane
this inactivates the Na+ channels
action potentials fail to spread along the muscle fibres, thus preventing muscle contraction in response to motor nerve activity

23
Q

1.05 NEUROMUSCULAR BLOCKER

Depolarising agent: succinylcholine (suxamethonium) - abs/distrib/elim

A

given IV
hydrolysed by plasma cholinesterase within a few minutes (a small percentage of people have an enzyme with much lower activity and action is prolonged)

24
Q

1.05 NEUROMUSCULAR BLOCKER

Depolarising agent: succinylcholine (suxamethonium) - clinical use

A

short-lasting paralysis to aid tracheal intubation and for short operative procedures
action is not reversed by anticholinesterases

25
Q

1.05 NEUROMUSCULAR BLOCKER

Depolarising agent: succinylcholine (suxamethonium) - adverse effects

A

hyperkalaemia (with possible cardiac arrhythmia)
hypotension, bradycardia
muscle pain (resulting from spasm during the initial depolarisation)
raised intraocular pressure
malignant hyperthermia (rarely, when used with halothane)

26
Q

1.06 NEUROMUSCULAR BLOCKER

Nicotinic antagonist: pancuronium, vecuronium, rocuronium, mivacurium, etc. - actions

A

non-depolarising neuromuscular blocker
paralysis of skeletal muscle

27
Q

1.06 NEUROMUSCULAR BLOCKER

Nicotinic antagonist: pancuronium, vecuronium, rocuronium, mivacurium, etc. - MOA

A

reversible competitive antagonism at muscle-type nicotinic receptors
inhibits binding of ACh to the receptors at the muscle end-plate
end-plate potential fails to reach threshold for initiation and propagation of the action potential along the muscle fibre
action reversed by anticholinesterases (e.g. neostigmine) or by sugammadex (for vecuronium and rocuronium)

28
Q

1.06 NEUROMUSCULAR BLOCKER

Nicotinic antagonist: pancuronium, vecuronium, rocuronium, mivacurium, etc. - abs/distrib/elim

A

given IV
rocuronium and mivacurium have faster onset (1-2min) and shorter duration of action (15min) compared to pancuronium (onset 2-3min, duration 1-2h)

29
Q

1.06 NEUROMUSCULAR BLOCKER

Nicotinic antagonist: pancuronium, vecuronium, rocuronium, mivacurium, etc. - clinical use

A

in general, anaesthesia and intensive care - aids tracheal intubation and mechanical ventilation, provides muscle relaxation for general surgery

30
Q

1.06 NEUROMUSCULAR BLOCKER

Nicotinic antagonist: pancuronium, vecuronium, rocuronium, mivacurium, etc. - adverse effects

A

tachycardia (muscarinic antagonist action)

31
Q

1.06 NEUROMUSCULAR BLOCKER

Nicotinic antagonist: pancuronium, vecuronium, rocuronium, mivacurium, etc. - special points

A

hypotension
skin flushing
bronchoconstriction due to histamine release

32
Q

1.07 PERIPHERAL ANTICHOLINESTERASES

Neostigmine, pyridostigmine, physostigmine - actions

A

peripheral cholinesterase inhibitors
parasympathomimetic: increased peristalsis; increased secretions; bradycardia; bronchoconstriction; decreased intraocular pressure
at the neuromuscular junction: fasciculation and increased twitch tension
CNS: agitation and dreaming

33
Q

1.07 PERIPHERAL ANTICHOLINESTERASES

Neostigmine, pyridostigmine, physostigmine - MOA

A

reversible inhibition of acetylcholinesterase reduces breakdown of ACh at cholinergic nerve endings, so potentiating transmitter action
binds to both esteratic and anionic sites in the enzyme
the esterase is carbamylated

34
Q

1.07 PERIPHERAL ANTICHOLINESTERASES

Neostigmine, pyridostigmine, physostigmine - abs/distrib/elim

A

given IV (to reverse neuromuscular block), by mouth (for myasthenia gravis)
mostly ionised, so low oral bioavailability and poor penetration of the blood-brain barrier
duration of action 2-4h

35
Q

1.07 PERIPHERAL ANTICHOLINESTERASES

Neostigmine, pyridostigmine, physostigmine - clinical use

A

neostigmine and pyridostigmine for myasthenia gravis
IV neostigmine for reversal of non-depolarising neuromuscular block
cholinesterase inhibitors in Alzheimer’s dementia

36
Q

1.07 PERIPHERAL ANTICHOLINESTERASES

Neostigmine, pyridostigmine, physostigmine - adverse effects

A

nausea, vomiting, diarrhoea, hypersalivation, bronchoconstriction
unwanted parasympathomimetic actions can be reduced by atropine

37
Q

1.08 NICOTINIC PARTIAL AGONISTS

Varenicline - actions

A

partial agonist activity at nicotinic receptors to alleviate smoking craving and withdrawal
reduces the rewarding and reinforcing pattern of smoking by blocking nicotine

38
Q

1.08 NICOTINIC PARTIAL AGONISTS

Varenicline - MOA

A

binds to α4β2 neuronal nicotinic acetylcholine receptors, but with lower degree of activity than nicotine
also exerts antagonistic effect by preventing nicotine from fully activating the α4β2 receptor

39
Q

1.08 NICOTINIC PARTIAL AGONISTS

Varenicline - abs/distrib/elim

A

given orally, with high bioavailability
steady-state reached within 4 days

40
Q

1.08 NICOTINIC PARTIAL AGONISTS

Varenicline - clinical use

A

smoking cessation in adults

41
Q

1.08 NICOTINIC PARTIAL AGONISTS

Varenicline - adverse effects

A

nausea, poor appetite, nightmares

Pharmacology (34 decks)

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