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Year 2 Pharma > Cholinomimetics > Flashcards

Cholinomimetics Flashcards

1
Q

What are the 5 muscarinic receptor subtypes?

A

M1 - Salivary glands, stomach, CNS
M2 - Heart
M3 - Salivary and sweat glands, bronchial/visceral SM, Eye
M4, M5 - CNS

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2
Q

How can muscarinic affects be abolished?

A

Using low doses of the antagonist atropine

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3
Q

What do larger doses of ACh do to the body after an atropine blockade of muscarinic receptors?

A

Induce effects similar to those caused by nicotine

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4
Q

Where do nicotine receptors exist?

A

On all post ganglionic neuronal cell bodies

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5
Q

Where do all ACh receptors exist?

A

On all post ganglionic neuronal cell bodies in ANS

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6
Q

What are nicotinic receptors?

A

FASTER ligand gated ion channels

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7
Q

What are the 5 subunits of nicotinic receptors?

A

alpha beta, gamma, delta, epsilion

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8
Q

What are the muscle types of subunits of nicotinic receptors?

A

2alpha, beta, delta, epsilion

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9
Q

What are the ganglion types of subunits of nicotinic receptors?

A

2alpha, 3beta

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10
Q

What does the subunit combination determine?

A

Ligand binding properties of the receptor

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11
Q

What are the effects of ACh like on nicotinic receptors?

A

Relatively weak

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12
Q

What does cholinergic innervation mediate in the eye?

A
  1. ciliary muscle contraction - near vision
  2. sphincter pupillae contraction - miosis and drainage of intra-ocular fluid
  3. lacrimation - tears
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13
Q

What is impeded in a glaucoma?

A

Contraction of the sphincter pupillae opens a pathway for aqueous humour, allowing drainage via the Canals of Schlemm thus reducing IOP

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14
Q

Where are the muscarinic receptors mainly located in the heart?

A

M2 AChR are located mainly in the atria and the nodes

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15
Q

What effects do the muscarinic receptors have on the cardiovascular system?

A

Decreased HR, CO, vasodilation
Depresses the heart by:
- Reduction of cAMP
- Decrease Ca2+ entry leading to lower CO
- Increase K+ efflux therefore decreasing HR

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16
Q

What does ACh act on in the vasculature?

A

Acts on vascular endothelial cells to stimulate NO release via M3 AChR

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17
Q

What is PNS innervation like in the vasculature?

A

Most blood vessels don’t have PNS innervation

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18
Q

What are the muscarinic effects on non vascular SM?

A

SM with PNS innervation contracts instead of relaxes so:
Lungs - bronchoconstriction
Gut - Increased peristalsis (can lead to GI pain)
Bladder - increased bladder emptying

19
Q

What are the muscarinic effects on exocrine glands?

A

Salivation
Increased bronchial and GI secretions
Increased sweating

20
Q

What are 2 examples of directly acting cholinomimetic drugs?

A

Bethanechol - choline ester

Pilocarpine - alkaloid

21
Q

What is bethanechol?

A

A choline ester - M2 AChR selective antagonist that is resistant to degradation, orally active and has limited access to the brain. Half life is 3-4 hrs.

22
Q

What is bethanechol used for?

A

Aid bladder emptying and enhance GI motility

23
Q

What is philocarpine?

A

A non-selective muscarinic agonist with good lipid solubility - attaches to any subtype of muscarinic receptor

24
Q

What is philocarpine used to treat?

A

Glaucoma

25
Q

What are indirectly acting cholinomimetic drugs used for?

A

Increasing the effect of normal PNS stimulation

26
Q

What are the two types of cholinesterase enzymes that are used to metabolise ACh to choline and acetate?

A

Acetylcholinesterase

Butyrylcholinesterase

27
Q

What are the properties of acetylcholinesterase? (3)

A

Found in synapses
Rapid
Highly selective for ACh

28
Q

Where is butyrylcholinesterase found?

A

in plasma and most tissues but not in synapses

29
Q

What is the specificity of butyrylcholinesterase?

A

Broad substrate specificity?

30
Q

What are the effects of cholinesterase inhibitors?

A

Low dose - causes enhanced muscarinic activity
Moderate dose - further enhancement, increased transmission of all ANS ganglia (inc nAChRs)
High dose TOXIC - depolarising block at ANS ganglia and NMJ

31
Q

What are examples of reversible antocholinesterases?

A

Physostigmine, neostigmine, donepezil

32
Q

What do reversible anticholinesterases do?

A

Donate a carbamyl gropu to the enzyme active site, blocking the active site - competitive

33
Q

What is physostigmine?

A

Tertiary amine that acts at post ganglionic PNS synapse

34
Q

What is physostigmine used to treat

A

Glaucoma (aids IOP reduction)

Atropine poisoning

35
Q

What are examples of irreversible anticholinesterases?

A

Ecothiopate, dyflos, sarin (all organophosphate compounds)

36
Q

What do irreversible anticholinesterases do?

A

Rapidly react to enzyme active site and leave a large blocking group - stable and resistant to hydrolysis

37
Q

What is ecothiopate?

A

A potent inhibitor of anticholinesterase?

38
Q

What is ecothiopate used to treat?

A

Glaucoma (eye drops) but it has a prolonged duration of action

39
Q

What are the side effects of ecothiopate?

A

Sweating, blurred vision, GI pain, bradycardia, hypotension, respiratory difficulty

40
Q

What is special about non- polar anticholinesterases and needs to be considered when giving doses?

A

They can cross the blood brain barrier therefore lose doses can cause excitation with possibility of convulsions and high doses can lead to unconsiousness, respiratory depression and death

41
Q

What drugs are used to treat alzheimers?

A

Donepezil and Tacrine

42
Q

How do the drugs that are used to teat alzheimers help?

A

They potentiate the central cholinergic transmission, relieving AD symptoms but does not affect degeration

43
Q

What is organophosphate poisoning?

A

Accidental exposure to organophosphates in insecticides or deliverate use as nerve agents can cause servere toxicity causing increase in muscarinic activity, CNS excitation and depolarising NM block

44
Q

What is the treatment for organophosphate poisoning?

A

Atropine in IV
Artificial respiration
Pralidoxime in IV

Year 2 Pharma (34 decks)

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