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Pharm > Cholinergic Agonists > Flashcards

Cholinergic Agonists Flashcards

1
Q

What is cholineacetyl transferase?

A

Enzyme that produces acetylcholine

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2
Q

Where is cholineacetyl transferase ound?

A

Corneal epithelium, iris, ciliary body, inner plexiform layer

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3
Q

Where is cholinesterase foudn in high concentration?

A

Iris and ciliary body sphincter muscles

But not in aqueous, vitreous or retinal vessels

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4
Q

Where are muscarinic receptors present?

A

Iris, ciliary body, retina

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5
Q

What are direct acting muscarinic agonists? Indirect acting? Examples

A

Direct acting - stimulate muscarinic receptors directly E.g. pilocarpine

Indirect acting - cholinesterase inhibitor by phosphoylation or by carbamylation physostigmine, pyridostigmine, demecarium, echothiopate

Both:
E.g. Carbachol

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6
Q

What actions to muscarinic agonists cause?

A

Miosis (stimulating iris sphincter muscle)
Accomomodation (stimualting ciliary muscle)
Decreased IOP (passive increase in aq outflow)

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7
Q

What are the uses of cholinergic agnoists?

A

Treating POAG and preventing AACG
Accommodative squints (decreasing the accommodative effort)

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8
Q

What mydriasis will pilocarpine reverese?

A

Reverse phenylephrine will be reversed

Atropine will not

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9
Q

What is used to diagnose Adie’s pupil

A

Pilocarpine 0.125% - very sensitive - will cause miosis

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10
Q

What are side effects of cholinergic agonists

A

Headache
Brow ache

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11
Q

How does echothiopate act?

A

Indirect muscarinic agonist
Inhibit cholinesterase by phosphorylation

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12
Q

How doees physostigmine act?

A

Indirect muscarinic agonist
Inhibit cholinesterase by carbamylation

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13
Q

Why does adding pilocarpine to a indirect acting muscarinic agonists?

A

Decrease miosis
As acetylcholine is more potent than pilocarpine

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14
Q

What are the effects on pressure of indirect acting muscarinic agonists?

A

IAMAProduce initian rise in intraocular pressure and evenutal hypotensive effect

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15
Q

What are the uses of indirect muscarinic agonists?

A

POAG
AACG

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16
Q

What are side effects of indirect muscarinic agonist?

A

Cataract
Hyperplasia of the iris pigment epithelium

17
Q

How do muscarinic antagonists work? E.g.

A

Compete with acetylcholine for receptor sites on the post-synaptic membrane

Tropicamide
Atropine
Cyclopentolate
Homatropine

Mydriatic effect by inhibiting iris sphincter muscle

Also cause inihibition of ciliary muscles resulting in cycloplegia

18
Q

Why does tropicamide have longer duration of action in pigmented eyes?

A

Binding of drugs by pigment accounts for decreased efficacy and latency of action in pigemented eyes

19
Q

How does atropine supplement antimuscarinic action?

A

Stimulating alpha adrenergic receptors on dilator muscles

20
Q

What are side effects of muscarinic antagonists?

A

Mild fever
Skin flushing

Can raise IOP through angle closure
May decrease aqueous outflow

Increased distension and risk of necrotising enterocolitis in neonates
Ataxic dysarthria, cerebellar signs
Increased risk fo seizures

Tachyarrhythmias

21
Q

What is the MOA of pyridostigmine? Physostigmine? Ecothiopate

A

Acetylcholinesterase inhibitor - increases availbility of ACh at NMJ
Half life of 6h

Physostigmine has a very short half life

Ecothiopate - long acting AChesterase inhibitor - irreversible can cause life threatening prolonged paralysis

22
Q

How does pilocarpine work?

A

Increased trabeculor outflow

Facilitaes aqueous drainage by constricting the iris and opening the meshwork from its action on ciliary muscle

23
Q

Why is pilocarpine CI in aqueous misdirection?

A

Contraction of ciliary muscle can lead to

Induced myopia

Forward displacement of the lens-iris diaphragm

24
Q

When is pilocarpine CI in angle closure? What is the treatment in these cases?

A

AC secondary to topiramate where aetiology is forward lens-iris diaphragm rotation

Preferred treatment is atropine which relaxes the ciliary body and allows lens-iris diaphragm to rotate posteriorly

Pharm (9 decks)

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