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Immunology Drugs > Anticholinergic Agents > Flashcards

Anticholinergic Agents Flashcards

1
Q

What is the function of anticholinergic drugs?

A

Oppose the physiological action of neurotransmitter acetylcholine

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2
Q

What are the classes of anticholinergic drugs?

A

Cholinoceptor blockers
Cholinesterase regenerators

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3
Q

What are cholinoceptor blockers?

A

Antagonists or inverse agonists that bind to muscarinic or nicotinic receptors and prevent the effects of ACh

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4
Q

What are cholinesterase regenerators?

A

Not receptor blockers but instead chemical antagonists of AChE inhibitors

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5
Q

What are the different classes under cholinoceptor blockers?

A

Antimuscarinic agents
Neuromuscular blockers
Ganglionic blockers

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6
Q

Which two classes make up the anti-nicotinic drugs?

A

Neuromuscular blockers and ganglionic blockers

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7
Q

Why are most antimuscarinic drugs non selective?

A

The amino acids composing the ligand binding pocket are conserved among all muscarinic receptor types

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8
Q

What is another name given to the cholinoceptor blockers?

A

Parasympatholytic agents

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9
Q

What is the main effect of Parasympatholytic agents?

A

Reduce the activity of the parasympathetic nervous system

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10
Q

Which organs do the parasympatholytic agents target?

Why?

A

Many organs like the eyes, respiratory, GIT, heart and the bladder

Because parasympathetic nerves are widely distributed

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11
Q

What does the response of the parasympatholytic agents depend on?

A

Specific drug and the dose used

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12
Q

What does Scopolamine usually cause?

A

Excitement and delirium

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13
Q

What are examples of antimuscarinic agents?

A

Atropine
Scopolamine
Tropicamide
Darifenacin / Oxybutynin
Ipratropium / Totropium
Benztropine / Trihexyphenidyl
Pirenzepine

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14
Q

What is Atropine?

A

An alkaloid found in a plant

Non-selective, reversible and competitive antagonist

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15
Q

What is the MOA of Atropine?

A

Binds to all five muscarinic receptors with high affinity

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16
Q

How can the blocking effect of the muscarinic receptors by Atropine be overcome?

A

Increasing concentration of muscarinic agonists

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17
Q

What are the PK of Atropine?

A

Lipid-soluble
Crosses membranes, including CNS, eye and other organs
Well distributed

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18
Q

What are the therapeutic uses of Atropine?

A

Antidote in treatment of AChE poisoning, overdose if muscarinic agonists or poisoning caused by consumption of mushrooms

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19
Q

What are the side effects of Atropine?

A

Dry mouth
Urinary retention
Blurred vision
Tachycardia
Constipation

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20
Q

What is Scopolamine?

A

Belladonna alkaloid

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21
Q

What are the therapeutic uses of Scopolamine?

A

Prevention of morning sickness and nausea

Treatment of poisoning by AChE

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22
Q

Why is Scopolamine recommended for the treatment of AChE poisoning compared to Atropine?

A

Readily crosses BBB
Greater action on CNS
Longer duration

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23
Q

What are the side effects of Scopolamine?

A

Short-term memory block
Sedation
Euphoria

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24
Q

What is Tropicamide?

A

Short acting antimuscarinic drug

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25
Q

What is the therapeutic use of Tropicamide?

A

Eye drops prior to retinal exams

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26
Q

What is the function of Tropcamide?

A

Produces mydriasis (dilation of pupil) for 6 hours

Inhibition of contraction of iris sphincter muscles

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27
Q

What are Darifenacin & Oxybutynin?

A

Synthetic atropine-like drugs

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28
Q

What is the therapeutic use of Darifenacin & Oxybutynin?

A

Treatment of overactive bladder

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29
Q

What are the clinical uses Ipratropium and Tiotropium?

A

Approved as bronchodilators for maintenance treatment of bronchospasm

Ashma & COPD

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30
Q

What are the clinical uses of Benzotropine and Trihexyphenidyl?

A

Treatment of Parkinson’s disease

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31
Q

What is Pirenzepine?

A

M1 selective antagonist

32
Q

What is the therapeutic use of Pirenzepine?

A

Treatment of peptic ulcers

33
Q

Which drugs under natural alkaloids?

A

Atropine
Scopolamine

34
Q

Which drugs are under tertiary amines?

A

Tropicamide
Oxybutynin
Benzotropine

35
Q

Which drugs are under quaternary amines?

A

Ipratropium
Tiotropium

36
Q

Which classes of antimuscarinic drugs are well absorbed from the GIT and conjunctival membranes?

A

Natural alkaloids and tertiary amines

37
Q

How are quaternary amines absorbed?

A

10 to 30% after oral administration

38
Q

Which antimuscarinic agent are widely distributed?

A

Atropine and tertiary amines
Significant levels are achieved in CNS within 30 minutes to 1 hour

39
Q

Which antimuscarinic agent is rapidly and gully distributed into CNS where it has greater effects than the rest?

A

Scopolamine

40
Q

Which antimuscarinic agents are poorly taken up by the brain?

A

Quaternary, they have no effect on the brain at low doses

41
Q

How is Atropine metabolised?

A

Partly by the liver and partially unchanged in the urine

42
Q

What are the two phases of Atropine elimination from the blood?

A
  1. The half-life of the RAPID phase is 2 hours
  2. The SLOW phase is approximately 13 hours
43
Q

How do Atropine’s effects decline?

A

Rapidly all organs (4 to 8 hours)
Except of the eye, where it lasts for days

44
Q

What are the contraindications of anticholinergic drugs?

A

Glaucoma, GIT disease, and urinary retention

45
Q

Why is narrow angle glaucoma a contraindication of anticholinergic drugs?

A

Even moderate doses can induce acute glaucoma which is a medical emergency

46
Q

Why are GIT disease or urinary retention contraindications for anticholinergic drugs?

A

Antimuscarinic drugs reduce contractility of bladder smooth muscle –> acute urinary retention

Reduction of GI motility may worsen symptoms of individuals with intestinal obstruction

47
Q

Why is Atropine contraindicated in narrow angle glaucom?

A

Atropine relaxes the ciliary muscles causing complete drainage obstruction of aqueous humor.

48
Q

What are neuromuscular blockers?

A

Quaternary amines that are structurally related to ACh.

Most are antagonists

49
Q

What is the prototype of neuromuscular blockers?

A

Tubocurarine

50
Q

Which is the neuromuscular blocker which is clinically used today?

A

Succinylcholine, agonist at the nicotinic receptor

51
Q

What is the MOA of nondepolarizing neuromuscular blockers?

A

Competitively block ACh transmission at the nicotinic receptors –> prevent depolarisation at the muscle cell membrane –> inhibit muscular contraction

52
Q

What can overcome the effects of the nondepolarizing neuromuscular blockers?

A

Increasing the amount of agonist, ACh or administrating cholinesterase inhibitors

53
Q

What are the general PK of the nondepolarizing neuromuscular blockers?

A

Given IV or IM
Quaternary amine structure prevents absorption from the gut
Poor penetration of the membranes, do not cross BBB
Eliminated in the bile

54
Q

What are the PK of Cisatracurium?

A

Degrades in the plasma
Onset: 2 to 8 minutes
Type: Intermediate, Competitive
Duration: 45 to 90 minutes
Mode of Elimination: Renal

55
Q

What are the PK of Rocuronium?

A

Onset: 0.9 to 1.7 minutes
Type: Intermediate, competitive
Duration: 36 to 73 minutes
Mode of Elimination: Hepatic (bile)

56
Q

What are the PK of Pancuronium?

A

Onset: 3 to 4 minutes
Type: Long, competitive
Duration: 85 to 100 minutes
Mode of Elimination: Renal & hepatic

57
Q

What are the PK of Succinylcholine?

A

Onset: 0.8 to 1.4 minutes
Type: Ultrashort, depolarising
Duration: 6 to 11 minutes
Mode of Elimination: Hydrolysis by plasma cholinesterases
Injected IV

58
Q

What is the only example of depolarising neuromuscular blocking drugs?

A

Succinylcholine

59
Q

What are the steps that Succinylcholine follows?

A
  1. signaling
  2. desensitization
  3. internalisation
  4. a) degradation
  5. b) recycling
60
Q

What is the MOA of depolarising neuromuscular blocking drugs?

A

Agonist bind to nicotinic receptors –> opening of the sodium channels –> depolarises the junction

61
Q

What is the difference between Succinylcholine and ACh?

A

Unlike ACh, Succinylcholine is more resistant to degradation by AChE –> remains attached for longer time –> depolarisation is longer

62
Q

What causes resistance to Succinylcholine, phase II (desensitisation) ?

A

Tension cannot be maintained in skeletal muscles without periods of repolarization –> muscle relaxation and paralysis

63
Q

What are the differences between the PK of Atropine & Succinylcholine?

A

Action of Succinylcholine is longer than that of ACh

64
Q

What will happen to Succinylcholine upon discontinuation?

A

Because it is still brief –> redistribution and rapid hydrolysis
Drug effects will rapidly disappear

65
Q

What are the side effects of neuromuscular blockers?

A
  1. Respiratory paralysis –> asphyxiation
  2. Autonomic effects –> cardiac muscarinic receptors are affected
  3. Hyperkalemia –> Succinylcholine
66
Q

What are the drug interactions of the Neuromuscular blockers?

A

Inhaled anesthetics –> potentiate and prolong the blockade

Aminoglycoside antibiotics
Antiarrhythmic drugs

67
Q

What happens if succinylcholine interacts with inhaled anaesthetics?

A

Malignant hypothermia
Early sign is contraction of jaw muscles

68
Q

What are the examples of ganglionic blockers?

A

Hezamethonium
Mecamylamine

69
Q

What do ganglionic blockers do?

A

Block nicotinic receptors at sympathetic and parasympathetic autonomic ganglia

70
Q

What were ganglionic receptor developed to treat?

A

Hypertension

71
Q

What limits their clinical use?

A

The lack of selectivity

72
Q

What are the effects of nicotine?

A

Increases alertness
Reduces circulation to extremities
Increases BP and HR
Relaxes muscles and enhances the release of dopamine & NE
Suppresses apetite

73
Q

What is the prototype of Cholinesterase regenerators?

A

Pralidoxime

74
Q

What is the MOA of Cholinesterase regenerators?

A

Reactivate AChE by an organophosphate agent

75
Q

How is the organophosphate agent reactivated?

A

The oxide group of Pralidoxime has high affinity for the phosphate group of organophosphate

Hydrolyses the bond if aging has not occurred

Enzyme is regenerated

76
Q

Why is Pralidoxime not as effective against the chemically different “carbamate” type AChE?

A

Carbamates do not have a phosphate group

Immunology Drugs (7 decks)

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