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Pharmacology - Exam 2 > Cholinergic Agonists > Flashcards

Cholinergic Agonists Flashcards

1
Q

Describe the cycle of ACh

A
  • Step 1: acetyl-CoA + choline –> Ach
  • Step 2: ACh stored in neurons
  • Step 3: ACh released via action potential stimulation
  • Step 4: ACh binds to receptor (ACh-R)
  • Step 5: AChesterase breaksdown ACh
  • Step 6: acetyl-CoA and choline recycled
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2
Q

What are the types of receptors that bind ACh?

A
  • muscarinic

- nicotinic

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3
Q

Define parasympathomimetic

A
  • produce actions that mimic those seen when ACh binds to muscarinic receptors of the parasympathetic NS
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4
Q

What is an example of a parasympathomimetic agent?

A
  • muscarine

- nicotine

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5
Q

Where are muscarinic receptors located?

A
  • postganglionic parasympathetic

i. e. autonomic effector organs

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6
Q

What are the differences in muscarinic receptor types?

A
  • M1, M3, & M5 lead to cellular excitation

- M2 & M4 inhibit cellular excitability

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7
Q

What role does ACh have at muscarinic receptors in the parasympathetic NS?

A
  • activate muscarinic receptors on target organs
    OR
  • binding receptors inhibits release of other NT
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8
Q

Where are nicotinic receptors located?

A
  • ganglionic level of both parasympathetic and sympathetic sides of ANS
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9
Q

What are the differences in nicotinic receptors?

A
  • Nm are located at somatic, neuromuscular junction (not in ANS)
  • Nn are located in CNS, adrenal medulla, and autonomic ganglia
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10
Q

What is ACh role at nicotinic receptors in the somatic NS?

A
  • primarily present at neuromuscular junction of skeletal M.

- binding of ACh creates positive stimulus (i.e. skeletal M. contraction)

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11
Q

What do nicotinic receptors at neuromuscular junction bind?

A
  • only ACh
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12
Q

Define cholinomimetic agent

A
  • nonACh compounds that mimic actions of ACh
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13
Q

What is the function of direct cholinomimetic agonists (i.e. stimulants)?

A
  • direct binding to ACh-R
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14
Q

What is the function of indirect cholinomimetic agonists (i.e. cholinesterase inhibitors)?

A
  • indirect cholinergic action by inhibiting ACh breakdown

[if ACh does not get broken down, it stays in synapse longer and continues to produce an effect]

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15
Q

What are the direct acting cholinomimetic groups with examples?

A
  • esters of choline i.e. ACh

- alkaloids i.e. muscarine & nicotine

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16
Q

What are the characteristics of choline esters?

A
  • hydrophilic (i.e. lipid insoluble)
  • hydrolyzed by AChesterase (AChE)
  • variations alter potency & susceptibilty to AChE
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17
Q

Describe choline esters

A
  • quaternary ammoniums
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18
Q

Describe alkaloids

A
  • typically tertiary amines but could be quaternary amine
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19
Q

What are the characteristics of alkaloids?

A
  • well absorbed after oral admin
  • hydrophobic (i.e. lipid soluble)
  • not susceptible to AChE
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20
Q

What is an advantage of being hydrophobic or lipid soluble?

A
  • able to cross BBB
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21
Q

What is the mechanism of action (MOA) of indirect acting cholinomimetics?

A
  • inhibit AChE thereby prolonging the presence and action of ACh at all ACh-R
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22
Q

What are the types of AChE inhibitors?

A
  • simple alcohols
  • carbamate esters
  • organophosphates
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23
Q

Describe the difference in binding among the AChE inhibitors

A
  • simple alcohols bind weakly and reversibly
  • carbamate esters bind reversibly but tighter
  • organophosphates bind nearly irreversibly
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24
Q

Which systems have similar effects for direct and indirect cholinomimetics?

A
  • eye
  • respiratory
  • GI
  • GU
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25
Q

Which systems have different effects for direct and indirect cholinomimetics?

A
  • CV
  • secretory glands
  • NS
  • neuromuscular junction
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26
Q

What is the eye sensitive to?

A
  • muscarinic agonists

- AChE inhibitors

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27
Q

What are the effects of cholinomimetics on the eye?

A
  • contraction of iris sphincter resulting in miosis
  • contraction of ciliary M. resulting in accommodation

Overall: pupilary constriction

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28
Q

What is the clinical significance of the effect of cholinomimetics on the eye?

A
  • assist with aqueous humor outflow to decrease IOP
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29
Q

What is the clinical use of cholinomimetics on the eye?

A
  • muscarinic agonists and AChE inhibitors decrease IOP in glaucoma patients
  • only given as drops to reduce risk of side effects to the heart
30
Q

What are examples of drugs used as cholinomimetics on the eye?

A
  • pilocarpine

- physostigmine

31
Q

What are the effects of cholinomimetics on the respiratory system?

A
  • bronchoconstriction

- stimulates mucus secretion in tracheobronchial tree

32
Q

What are the clinical uses of cholinomimetics on the respiratory system?

A
  • none

- anticholinergics increase airflow

33
Q

What are the effects of cholinomimetics on the GI tract?

A
  • increase secretory and motor activity & peristalsis

- relaxes sphincters

34
Q

What are the clinical uses of cholinomimetics on the GI tract?

A
  • use agents to correct depressed smooth muscle activity and increase motility
  • i.e. post-op & in patients with congenital megacolon
35
Q

What is an example of a cholinomimetics used on the GI tract?

A
  • neostigmine
36
Q

What is the effect of cholinomimetics on the GU tract?

A
  • triggers voiding the bladder via contraction of detrusor muscle and relaxation of trigone and sphincter muscles
37
Q

What are the clinical uses of cholinomimetics on the GU tract?

A
  • use agents to correct depressed smooth muscle activity

- i.e. treat urinary retention

38
Q

What are examples of cholinomimetics used on the GU tract?

A
  • bethanecol

- neostigmine

39
Q

What are the effects of direct cholinomimetics on the CV system?

A
  • two effect of muscarinic agonists
  • reduce peripheral vascular resistance through vasodilation which decreases BP which can cause an indirect reflex increase in HR
  • decreased HR through decreased rate of SA node firing leading to bradycardia which reduces CO
40
Q

Why are direct cholinomimetics not often used on the CV system?

A
  • there are other drugs that do the same effect but better and more predictably
41
Q

What are the effects of indirect cholinomimetics on the CV system?

A
  • AChE inhibitors increase cholinergic activity
  • both sympathetic and parasympathetic actions on the heart lead to negative chronotropic and ionotropic effects (bradycardia and decreased CO, respectively)
42
Q

Which has a greater effect on the heart, sympathetic or parasympathetic?

A
  • parasympathetic –> observe more parasympathetic results
43
Q

What is the effect of an indirect cholinomimetics on the cardia and vascular smooth muscle?

A
  • modest drop in BP
44
Q

What does chronotropic refer to?

A
  • HR
45
Q

What does inotropic refer to?

A
  • contractility
46
Q

What are the effects of cholinomimetics on misc. secretory glands?

A
  • sweat glands causing diaphoresis to regulate T
  • increased lacrimation
  • increased mucus in nasopharynx
47
Q

What are the effects of direct cholinomimetics on the nicotinic receptors in the CNS?

A
  • induce tremor
  • stimulate emesis (vomit)
  • stimulate respiratory center
48
Q

What are the effects of direct cholinomimetics on the muscarinic receptors in the CNS?

A
  • induce tremor
  • cause hypothermia
  • interfere with nociception
49
Q

What is the effect of indirect cholinomimetics on the CNS?

A
  • [low] have little effect

- [high] can causes convulsions, coma, & respiratory arrest

50
Q

What are two clinical indications for cholinomimetics for CNS conditions?

A
  • alzheimer’s

- smoking cessation

51
Q

What is the effect of ACh at the neuromuscular junction?

A
  • contraction of skeletal m.
52
Q

What is the effect of low dose indirect cholinomimetics on the neuromuscular junction?

A
  • prolong effects of ACh thereby increasing strength of m. contraction
53
Q

What is the effect of medium does indirect cholinomimetics on the neuromuscular junction?

A
  • may cause m. to fibrillate making the m. less effective
54
Q

What is the effect of high does indirect cholinomimetics on the neuromuscular junction?

A
  • blocks m. depolarization leading to paralysis
55
Q

What is the pathophysiology of myasthenia gravis?

A
  • autoimmune - antibodies target nicotinic receptors on skeletal m. and block ACh binding
  • cholinomimetics effective tx
56
Q

What are examples of drugs used to tx myasthenia gravis?

A
  • pyridostigmine

- neostigmine

57
Q

What is an effective treatment for anticholinergic intoxication?

A
  • cholinomimetics
  • increase the amount of ACh
  • AChE inhibitors (i.e. physostigmine)
58
Q

What are the types of cholinomimetics toxicities?

A
  • receptor (muscarinic v. nicotinic)

- MOA (direct cholinomimetics v. AChE inhibitor)

59
Q

What are the signs of toxicity of direct muscarinic agonists?

A
  • SLUG (salivation, lacrimation, uriniation, defecation)

- N/V, diarrhea, uriniary urgency, sweating, cutaneous vasodilation, bronchial constriction)

60
Q

What is the treatment for toxicity of direct muscarinic agonists?

A
  • atropine, an anticholinergic
61
Q

What are the signs of acute nicotine toxicity?

A
  • CNS stimulation (convulsions, coma, respiratory arrest)
  • skeletal m. depolarization (stops contractions)
  • HTN & cardiac arrhythmias
62
Q

What is the treatment for acute nicotine toxicity?

A
  • supportive
63
Q

What are the symptoms of cholinesterase (AChE) inhibitor toxicity?

A
  • DUMBBELSS

- diarrhea, urination, miosis, bradycardia, bronchoconstriction, emesis, lacrimation, salivation, sweating

64
Q

What are the treatments for AChE toxicity?

A
  • monitor vitals
  • decontaminate
  • antidote with 2-PAM
65
Q

What is 2-PAM an antidote for and how does it work?

A
  • organophosphates

- reactivates inhibited AChE before the full covalent bond forms through “aging”

66
Q

Where are cholinergic receptors found in the ANS?

A
  • preganglionic sympathetic and parasympathetic

- postganglionic parasympathetic

67
Q

What type of neurons release NE?

A
  • postganglionic sympathetic
68
Q

What effect would a muscarinic agonist have on the sympathetic portion of the autonomic nervous system?

A
  • none, trick question
69
Q

What is the name of the enzyme that metabolizes ACh?

A
  • acetylcholinesterase (AChE)
70
Q

Why do organophosphates inhibit AChE for so long compared to other types of AChE inhibitors?

A
  • covalent bonding
71
Q

What effect does nicotine have in toxic concentrations in humans?

A
  • seizures, coma, respiratory arrest

Pharmacology - Exam 2 (4 decks)

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