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Foundations To Medicine 2 > Cholinergic Agonists And Antagonists > Flashcards

Cholinergic Agonists And Antagonists Flashcards

1
Q

What are the types of cholinergic agonists ?

A

Direct acting: bind to and activates muscuranic or nicotinic receptors

Indirect acting: inhibit acetylcholinesterase

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2
Q

Summarize direct acting cholinergic agonists

A
  • some are selective fir the muscuranic or nicotinic receptors
  • many have effects on both receptors
  • Most therapeutically useful drugs preferentially activate muscuranic drugs
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3
Q

What are the cardiovascular effects of direct acting effects of ACh?

A

Direct effects of acetylcholine

  • vasodilation (M3 effect)
  • Decrease in cardiac ratev(M2 effect)
  • Decrease in rate of conduction in the SA and AV nodes (M2 effect)
  • Decrease in force of contraction (M2 effect)

Some of the direct effects can be obscured by barireceotor reflexes

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4
Q

What are cardiovascular effects of acetylcholine IV injections?

A
  • IV injection of a small dose of acetylcholine produces a fall in blood pressure due to vasodilation (M3 effect) usually accompanied by reflex tachycardia
  • larger doses of acetylcholine cause vasodilation, a fall in blood pressure (M3 effect) and bradychardia (M2 effect)
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5
Q

What are the effects of vasculature(endothelial cells)?

A

Effects of acetylcholine: release of NO and vasodilation

Decrease in BP

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6
Q

What is the effect of acetylcholine on eye iris?

A

Miosis

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7
Q

What is the effect of acetylcholine on ciliary muscle?

A

Accommodation of lens to near vision

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8
Q

What is the effect of acetylcholine on salivary/ sweat/ lacrimal glands?

A

Increased secretions

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9
Q

What is the effect of acetylcholine on bronchi?

A

Constriction

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10
Q

What is the effect of acetylcholine on the heart?

A

Decreased, heart rate and conduction velocity

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11
Q

What is the effect of acetylcholine on the GI tract?

A

Increased tone & peristaltic activity; relaxation of sphincters

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12
Q

What is the effect of acetylcholine on the urinary bladder?

A

Contraction of detrusor muscle; relaxation of sphincter

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13
Q

What happens to acetylcholine in large doses if muscuranic effects are blocked by muscuranic antagonists (atropine)?

A

Fir thus reason, drugs like atropine produce nicotinic effects at large doses

Vasoconstriction and increase in blood pressure

These effects are due to stimulation of sympathetic ganglia and release of epinephrine from the adrenal medulla

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14
Q

What are the choline esters?

A
  • Acetylcholine
  • Methanecnoline
  • Bethanechol
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15
Q

What are choline esters?

A

Choline esters are quartenary ammonium

  • Poorly absorbed and poorly distributed into the CNS
  • They differ in their susceptibility to hydrolysis by cholinesterase
  • Acetylcholine is very rapidly hydrolyzed
  • Methanecholine and Bethanechol are more resistant to hydrolysis by cholinesterase
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16
Q

What are the acetylcholine?

A

Muscuranic and nicotinic agonist

Uses: used to obtain miosis after delivery of the lens in cataract surgery and other procedures where rapid miosis is required

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17
Q

What is Bethanechol?

A

Muscuranic agonist

Uses:

  • Postoperative urinary retention
  • Antony of the urinary bladder
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18
Q

What is methanechol?

A

Muscuranic agonist

Uses: diagnosis of bronchial airway hyperactivity in subjects who do not have clinically appearent asthma

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19
Q

What are the natural alkaloids?

A
  • pilocarpine

- nicotine

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20
Q

What is pilocarpine?

A
  • Partial Muscuranic agonist
  • tertiary amine
  • Stable to hydrolysis by acetylcholinesterase

Uses:

  • Glaucoma
  • Treatment of dry mouth due to radiotherapy fir cancer of head and neck
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21
Q

What are the adverse effects of muscuranic agonists ?

A

The adverse eff3crs mimic the effects of generalized cholinergic stimulation:
-Sweating

  • Salivation
  • Flushing
  • Low blood pressure
  • Nausea
  • Abdominal pain
  • Diarrhea
  • Bronchospasm
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22
Q

What is nicotine?

A

Tertiary amine

  • Agonist at nicotinic receptors
  • Depending on the dose, nicotine depolarizes autonomic ganglia, resulting first in stimulation and then in paralysis
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23
Q

What are the actions of nicotine?

A

Low dose: ganglionic stimulation by depolarization

The response resembles simulataneous discharge of both parasympathetic and sympathetic nervous systems

High dose: ganglionic blockade and neuromuscular blockade

24
Q

What are the uses of nicotine?

A

-Smoking cessation therapy

25
Q

What are the indirect-acting cholinergic agents(anticholinesterases)?

A
  1. Edrophonium
  2. Carbamates
    • Physostigmine, neostigmine, pyridostigmine
  3. Orangophosphates
    • Malathion, sarin
26
Q

What is the mechanism of action of anticholinesterase?

A

Cholinesterase inhibitors, act by inhibiting acetylcholinesterase: they increase concentration of endogenous acetylcholine

27
Q

What is the mechanism of action 9f edrophonium?

A

Binds reversibly to the active site of the enzyme. This inhibition is short .

28
Q

What is the mechanism of action of carbamates?

A

Form a covalent bond with the enzyme

29
Q

What is the mechanism of action of orangophosphates?

A

Phosphorylate the enzyme. The covalent bond formed is extremely stable and hydrolyzes very slowly

30
Q

Summarize organ system effects of the anticholinesterases

A
  • Antivholinesterases amplify the action of endogenous acetylcholine
  • Therefore their effects are similar (but not always identical) to the effects of the direct-acting cholinomimmetic agents
31
Q

What are the special effects of cholinesterase inhibitors?

A

Cardiovascular system: in. The vascular smooth muscle cholinesterase inhibitirs gave minimal effects because most vascular beds lack cholinergic innervation

Neuromuscular junction: cholinesterase inhibitors increase strength of contraction

  • Useful to reverse action of nomdepolarizing neuromuscular blockers
  • Useful in myasthenia Gravis
32
Q

What are the properties of edrophonium?

A

Quaternary ammonium

-doesn’t enter CNS

Uses: diagnosis of myasthenia Gravis : edrophonium IV leads to rapid increase in muscle strength

Used to reverse the neuromuscular block produced by nom-depolarizing muscular blockers

33
Q

What are the properties of physostigmine?

A

Tertiary amine

-can enter and stimulate CNS

Uses: treatment of overdoses of anti cholinergic drugs

34
Q

What are the properties of neostigmine?

A
  • Quatenary ammonium
  • Doesn’t enter CNS

Uses:

  • Urinary retention
  • Reversal of effects of non-depolarizing neuromuscular blockers after surgery
  • treatment of myasthenia Gravis
35
Q

What are the properties of pyridistigmine ?

A

Quatenary ammonium

-Doesn’t enter CNSZ

Uses:
-treatment of myasthenia Gravis

36
Q

What are orangophosphates?

A
  • synthetic compounds

- many are extremely toxic

37
Q

Give examples of orangophosphates that are also insecticides

A

Malathion

Sarin- among the most potent synthetic toxic agents known

38
Q

What are the belladonna alkaloids?

A

Atropine & scopolamine

39
Q

What is atropine?

A
  • prototype of Muscuranic antagonists
  • reversible competitive antagonist at muscuranic receptors
  • Tertiary amine: both central and peripheral Muscuranic blocker
40
Q

What are the actions of atropine?

A

Eye: mydriasis & cycloplegia (M3 blockade )

GI: reduces gastric motility (M3 blocksde)

Urinary system: decreases hypermotility of urinary bladder (M3 blocksde )

CV system: Moderate to high therapeutic doses cause tachycardia (Atrial M2 blockade)

Secretions: Salicary, sweat and lacrimal glands are blocked. Inhibitions of sweat glands may cause high body temperature (M3 blockade)

41
Q

What are the uses of atropine?

A
  • antidote for cholinergic agonists

- to block respiratory tract secretions prior to surgery

42
Q

What are the adverse effects of atropine?

A
  • dry mouth, blurred vision, sandy eyes, tachycardia, constipation, urinary retention
  • effects on CNS: rest,Essenes, confusion, hallucinations, delirium
43
Q

What are the uses of scopolamine?

A

Prevention of motion sickness

44
Q

What are the synthetic and semisynthetic muscuran8c antagonists?

A
  • Quatenary ammonium Muscuranic antagonists

- Tertiary amine Muscuranic antagonists

45
Q

What is an example of a Quatenary ammonium Muscuranic antagonists?

A

Ipratropium

-used in the treatment of chronic obstructive pulmonary disease and asthma

46
Q

Give an example of a tertiary amine Muscuranic antagonist

A

Tropocamide

  • used as myristic fir fundus copy
  • Produces mydriasis with cycloplegia
47
Q

What are the contraindications of using antimuscuranic agents?

A
  • contraindicated in patients with angle-closure glaucoma

- Should be used with caution in patients with prostatic hypertrophy and in the elderly

48
Q

How May ganglion blocking occur?

A

Occurs by

-By prolonged depolarization example: nicotine

Or

-By antagonism of nicotinic receptors. Example:hexamethonium

49
Q

What are the uses of ganglion blockers?

A

Hexamethonium was used fir hypertension in the past

Due to their adverse effects ganglion blockers have been replaced by superior anti hypertensive agents

50
Q

What are the Pharmological uses of ganglion blockers ?

A

Effects of ganglion-blockers can be predicted by a knowledge of which division kf the autonomic nervous system exercises DOMINANT CONTROL of various organs

The effect of the ganglion blockers is to remove the dominant control

51
Q

What are the types of neuromuscular blockers ?

A
  • competitive antagonists (nondepolarizing blockers)

- agonists (depolarizing blockers)

52
Q

Explain an example of non depolarizing neuromuscular blockers

A

Tubocurarine is the prototype

Mechanism of action: competitive antagonists

Uses: as adjuvant in anaesthsia during surgery to relax skeletal muscle

53
Q

Give an example of depolaarizing neuromuscular blockers

A

Mechanism of action: succinylcholine binds to the nicotinic receptor and depolarizipes the junction. Pers8sts in the synaptic cleft, stimulating the receptor: receptor desensitizes

-this leads to the flaccid paralysis

Uses:
-rapid endotracheal intubation

-ECT

54
Q

What drugs act presynaotically ?

A

Inhibitors of acetylcholine release

55
Q

What is the effect of the botulinum toxin?

A
  • injected locally into muscles for treatment 8f several s8seases involving muscle spasms
  • Also approved for cosmetic treatment of facial wrinkles

Foundations To Medicine 2 (37 decks)

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