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PHA 3112 > 2.3 - Cholinergic Drugs > Flashcards

2.3 - Cholinergic Drugs Flashcards

1
Q

What is a cholinolytic?

A

A drug that blocks ACh-related effects.

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1
Q

What is a cholinomimetic?

A

A drug that mimics ACh
–> Directly as cholinergic agonist
–> Indirectly as an acetylcholinesterase inhibitor

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2
Q

Muscarinic agonists are also called:

A

Parasympathomimetics

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3
Q

What is the mechanism of action of muscarinic agonists? What does this result in?

A

Stimulates muscarinic receptors
–> Decreased heart rate, constriction of lung bronchi, mieosis
SLUDGE (salivation, lacrimation, urination, diaphoresis, GI motility, emesis) + any other PSNS effects

Note: Sweat glands are stimulates by SNS, but are under control of M3 receptors.

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4
Q

What is bethanechol? What is its use? Are there any special considerations for it?

A

A muscarinic agonist - used to treat urinary retention and intestinal paralysis

Charged molecule: poor oral absorption

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5
Q

What kinds of drugs are pilocarpine and carbachol? What are they given to treat?

A

Muscarinic Agonist:
Used to treat glaucoma (reduce intraocular pressure) and xerostomia.

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6
Q

What kind of muscarinic agonist is found in the betel nut, a fruit of the areca palm?

A

Arecoline

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7
Q

What kinds of mushrooms contain muscarine? What are the dangers if ingested? How can it be treated?

A

Mushrooms such as: amanita muscaria, inocybe, clitocybe

Toxicity due to SLUDGE+
Treat with muscarinic antagonist

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8
Q

What are the reversible AChE inhibitors? What differentiates them from one another?

A

Neostigmine
–> Charged

Physostigmine
–> Neutral

Edrophonium
–> Short-acting

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9
Q

Why might you administer a charged instead of a neutral drug?

A

A charged drug cannot easily cross the BBB, a neutral one can.

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10
Q

What is the mechanism of action of reversible AChE inhibitors?

A

Temporarily inactivates acetylcholinesterase, resulting in increased ACh levels.

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11
Q

Why might you use a reversible AChE inhibitor? (indications)

A

Treatment of myasthenia gravis, paralysis due to non-depolarizing neuromuscular blockers, or as treatment for alzeimers disease.

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12
Q

What are some AChE inhibitors used to treat Alzeimers?

A

Galantamine, Donepezil, Rivastigmine.

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13
Q

What are some contraindications for AChE inhibitors?

A

GI or urinary obstruction, asthma

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14
Q

What are some adverse effects of AChE inhibitors?

A

Excessive stimulation of muscarinic or neuromuscular receptors

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15
Q

What is myasthenia gravis?

A

An autoimmune disease linked to defective transmission at the neuromuscular junction, resulting is inactivation of Ach receptors by autoantibodies.
–> Results in muscular weakness

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16
Q

Why might reversible AChE inhibitors be used to treat myasthenia gravis?

A

Increasing the amount of ACh in neuromuscular junction means more chance that some NT will bind with the muscarinic receptors that aren’t inactivated by antibodies.

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17
Q

What kind of drugs are the following: Echothiophate, insecticides (melathion), nerve gases (sarin, tabun, XV)

A

Irreversible AChE inhibitors

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18
Q

What are effects of irreversible AChE inhibitors?

A

Excessive muscarinic stimulation, which then leads to inhibition of neuromuscular transmission.

19
Q

How do you treat exposure to to irreversible AChE inhibitors?

A

If caught quickly enough, they can be made reversible: Pralidoxime can reactivate inhibited AChE if caught quickly enough.

If not caught quickly enough: Atropine, oxygen/vents, diazepam (suppresses seizures, anxiolytics)

20
Q

Which drug can reactivate irreversibly inhibited AChE if the effects are caught quickly enough?

A

Pralidoxime

21
Q

What plant is atropine from?

A

Atropa belladonna

22
Q

What are some examples of muscarinic antagonists?

A

Atropine, tolterodine, oxybutynin, solifenacin, scopolamine

23
Q

What is the mechanism of action of muscarinic antagonists?

A

Block muscarinic receptors

24
Q

What are the effects of muscarinic antagonists?

A

Tachycardia, decreased GI secretions and motility, relaxation of bronchi, mydriasis and cycloplegia (loss of accomodation)

25
Q

What is cycloplegia?

A

Loss of accommodation abilities

26
Q

What is the indication for use of muscarinic antagonists?

A

To reduce urinary incontinents, GI hypermobility, Dry out secretions (for pre-op and palliative), eye exam or surgery, treatment of muscarinic poisoning, treatment of asthma

27
Q

Why might you want to administer muscarinic antagonists to individuals on palliative?

A

To reduce respiratory secretions that cause death rattle sounds.

28
Q

What are the adverse effects of muscarinic antagonists

A

–> Xerostomia, anhidrosis (lack of sweat), dry eyes, urinary retention, constipation, blurred vision, photophobia.

At high doses: psychosis and delirium

29
Q

Why might muscarinic antagonists cause psychosis or delirium?

A

They cause overexcitation of the CNS

30
Q

What is scopolamine?

A

A muscarinic antagonist that is administered as a transdermal patch as an antiemetic or inhibit secretions.

31
Q

What do neuromuscular blockers do?

A

Block nicotinic receptor on skeletal muscle

32
Q

Most neuromuscular blockers are what kind of molecule?

A

Permanently charged ammonium compounds and are therefore administered parenterally.

33
Q

What are the uses of neuromuscular blockers?

A

–> Relaxation during surgery
–> Endotracheal intubation, mechanical ventilation.

34
Q

What are the adverse effects of neuromuscular blockers?

A

Excessive paralysis can result in cessation of breathing.

35
Q

How can you reverse the effects of competitive neuromuscular blockers?

A

AChE inhibitors can reverse the effects of competitive antagonism (not with something that bombards the muscle with ACh, such as succinylcholine)

36
Q

What are the two mechanisms of action for neuromuscular blockers?

A
  1. non-depolarizing blockers (competitive inhibition)
    –> Competes with ACh for binding to muscle nicotinic receptors
  2. Depolarizing blockers
    –> Overstimulates muscle until it is inactivates
37
Q

All non-depolarizing neuromuscular blockers are derived form which plant? Give examples of these drugs.

A

All from the Cucare plan
–> tubocurarine, rocuronium, cisatracurium

38
Q

Blockade of muscle contraction by non-depolarizing blockers occurs only after more than ____% of receptors are blocked.

A

70%

39
Q

What kind of muscles are most/least sensitive to non-depolarizing neuromuscular blockers?

A

Fast twitch are more sensitive than slow twitch - respiratory muscles are moderately resistant.

40
Q

What is an example of a depolarizing neuromuscular blocker?

A

Succinylcholine

41
Q

How long does succinylcholine last when administered? Why?

A

Very short duration - 5 mins
–> Metabolized by plasma cholinesterase.

42
Q

Depolarizing NM blockers can lead to which complication?

A

Malignant Hyperthermia
–> Dangerously high body temp, rigid muscles or spams, and tachycardia
Can be fatal without prompt treatment, treated with dantrolene (which blocks calcium release from intracellular sarcoplasmic reticulum)

43
Q

How can malignant hyperthermia be treated?

A

Dantrolene
–> Blocks calcium release from intracellular sarcoplasmic reticulum.

44
Q

What is a possible consequence of administering an AChE inhibitor?

A

Cholinergic Crisis
–> Excessive acetylcholine levels at all receptors, which leads to repetitive overstimulation of nicotinic receptors on skeletal muscle and paralysis.

45
Q

How would you check if a person with myasthenia gravis is being under or overmedicated if they exhibit facial paralysis?

A

By administering edrophonium, a short acting reversible inhibitor of AChE.
If the symptoms improve - undermedicated myasthenia gravis
If they get worse or exhibit SLUDGE+, they are in a cholinergic crisis.

PHA 3112 (22 decks)

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