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PART ONE REVISION. > PHARMACOLOGY - Miosis and Mydriasis > Flashcards

PHARMACOLOGY - Miosis and Mydriasis Flashcards

1
Q

What are the effects of atropine - anti-muscarinic (2 ocular, 3 systemic)

A

Ocular
1. mydriasis via iris sphincter muscle paralysis
2. cycloplegia via ciliary body paralysis

Systemic
3. Sedatory effect
4. Delays gastric emptying
5. Reduces sweating

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2
Q

What are the mechanism of pilocarpine? (6)

A

DIRECT muscaranic agonist - acts on muscarinic / Ach receptor

  1. MIOSIS - iris sphincter contraction
  2. ACCOMODATION - ciliary muscle contraction (accomodative spasm)
  3. REDUCES IOP - ciliary muscle contraction increases tension of scleral spur by pulling is posteriorly and internally –> opening of trabecular meshwork (conventional route)
  4. MYOPIA - ciliary muscle contraction
  5. VASCULAR PERMEABILITY - increases so should be avoided in uveitis.
  6. REVERSAL OF MYDRIASIS - only ones caused by atropine, not phenylephrine.
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3
Q

Which drugs can reverse atropine mydriasis?

Which drugs can reverse phenylephrine mydriasis?

A
  1. Pilocarpine, thymoxamine (more effective)
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4
Q

What are the effects of apraclonidine? (3)

A
  1. Mydriasis
  2. Eyelid retraction
  3. Conjunctival blanching
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5
Q

What is the main ocular side effects of brimonidine / apraclonidine?

A

After 1 year - allergic conjunctivitis, follicular conjunctivitis

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6
Q

Which drugs are alpha-1 adrenergic agonists?

Which drugs are alpha-2 adrenergic agonists?

A

Alpha-1 : phenylephrine
Alpha-2: apraclonidine, brimonidine

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7
Q

Which drug relaxes the ciliary body?

A

Atropine

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8
Q

Which drugs are parasympathetic antagonists?

A
  1. Cyclopentolate
  2. Tropicamide
  3. Atropine
  4. Phenothiazine
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9
Q

What is the mechanism of action of phenylephrine?

A

Non selective alpha agonist

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10
Q

What is the mechanism of action of tropicamide?

A

It is a muscarinic antagonist - blocks parasympathetic pathway.

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11
Q

what are the side effects of tropicamide?

A
  1. precipitates angle closure
  2. exacerbates ataxic dysarthia
  3. cerebellar signs
  4. increases risk of seizure
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12
Q

In what instances are alpha-2-agonists contraindicated? (2)

A
  1. Potentiates hypertensive crisis with monoamine oxidase inhibitors
  2. WIth TCAs, its IOP effect is removed.
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13
Q

What is the effect of muscarinic agonists, example? (3)

A

Direct - pilocarpine
Indirect - carbachol - inhibits cholinesterase

  1. Miosis
  2. Accomodation
  3. Decreased intraocular pressure
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14
Q

What are the main muscarinic agonists and antagonists?

A

Musacrinic agonist - pilocarpine, carbachol

Muscarinic antagonist - tropicamide (short acting 6 hours), cyclopentolate (24 hours) atropine (7 days)

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15
Q

What is the order of potency for muscarinic antagonists?

A

atropine > cyclopentolate > homatropine > tropicamide

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16
Q

What is the mechanism of action of apraclonidine?

A

alpha-2-adrenergic agonist (partial) –> potent systemic anti-hypertensive –> causes mydriasis

Acts on the presynaptic nerve endings and are inhibitory –> prevent further release of neurotransmitter

Has very little alpha-1 activity (use in Horners)

17
Q

What are the ocular side effects of pilocarpine? (8)

A
  1. Miosis
  2. Induced myopia (myopic shift)
  3. Accomodative spasm
  4. Conjunctival vascular congestion
  5. Punctal stenosis
  6. Cataract formation
  7. Retinal detachment (causes contraction of ciliary body, pushes everything forward - caution in myopic patients)
  8. Headaches/brow ache
18
Q

What is the general actions of adrenergic agonists (4)

A
  1. Increase aqueous outflow by stimulating trabecular meshwork
  2. Ciliary muscle relaxation
  3. Contraction of Muller’s muscle –> ptosis relief
  4. Conjunctival vessel constriction
19
Q

Which drugs are alpha-1 adrenergic agonists?

Which drugs are alpha-2 adrenergic agonists?

A

Alpha-1 : phenylephrine
Alpha-2: aproclonidine, brimonidine (selective)

20
Q

What is the mechanism of action of cocaine?

A

inhibits reuptake of monoamines (adrenaline and noradrenaline) at the synaptic space

21
Q

Accomodation occurs with parasympathetic or sympathetic control?

A

parasympathetic control

22
Q

What is the mechanism of action of brimonidine?

A

Selective alpha-2 agonist
1. Reduces aqueous production by interfering with adenylyl cyclase

  1. Increases outflow by stimulating TM adrenergic receptors
  2. Induces miosis
23
Q

What are the side effects of brimonidine?

A

Induces CMO in aphakia, allergic blepharoconjunctivitis,

Contraindicated in heart block and bradycardia

24
Q

What is an example of an adrenergic antagonist? (2)

A

Beta blockers - timolol (block beta adrenergic receptors)

Guanethidine - inhibits release of noradrenaline from nerve terminals (inhibits mullers muscle to lead to a narrow palpebral fissure)

25
Q

What is the mechanism of action of hydroxyamphetamine?

A

stimulates release of noradrenaline from nerve terminals.
Differentiates between pre and post-ganglionic causes of Horner’s syndrome.

26
Q

What is the mechanism of action of botolinium toxin?

A

Inhibits ACh release at the neuromuscular junction.

27
Q

Important table regarding dilation in Horner’s

A
28
Q

What drugs are direct acting parasympathomimetic (ACh receptor agonist)?

What drugs are indirect acting parasympathomimeter (cholinesterase inhibitor)?

A
  1. pilocarpine
  2. physostigmine
29
Q

alpha 1 agonists vs alpha 2 agonists

A

Alpha-1 agonists are excitatory, principally causing smooth muscle contraction, as in the contraction of the dilator pupillae muscle. This dilatation causes an early rise in IOP.

Alpha-2 agonists occur mainly on the presynaptic nerve endings and are inhibitory as they prevent further release of neurotransmitter. Alpha-2 agonists such as clonidine cause a reduction in IOP and this is thought to be mediated centrally by the stimulation of the medullopontine sympathetic nerve and by reducing aqueous production locally.

Apraclonidine is a partial alpha-2 agonist; it has very little alpha-1 activity.

30
Q

Whats the difference between apraclonidine and brimonidine and phenylephrine?

A

phenylephrine is a synthetic sympathetic agonist that directly acts on alpha receptors

apraclonidine and brimonidine are both selective alpha-2 agonists. Brimonidine causes miosis.

31
Q

How is adrenaline formed?

A

From the meythylation of noradrenaline

32
Q

How is noradrenaline formed?

A

hydroxylation of tyrosine causes DOPA synthesis which converts to dopamine which coverts to noradrenaline.

33
Q

What are the main miotic agents? (6)

A
  1. Pilocarpine - stimulates ACh muscarinic receptors
  2. Carbachol - increases ACh release
  3. Alpha blockers - they paralyse the sphincter dilator muscle (brimonidine)
  4. Physostigmine - inhibits acetylcholinesterases –> Increased ACh in synaptic cleft.
  5. Heroine - reduces cortical inhibition of Edinger-Westphal nucleus
  6. Guanethidine (inhibits noradrenaline release from nerve terminals).
34
Q

Which mydriatic drug does not inhibit accomodation?

A

Phenylephrine

35
Q

Table of mydriatic drops - onset and duration.

A
36
Q

Diagram of mydriasis and miosis pupil effects

A
37
Q

Which drug can cause rebound miosis?

A

phenylephrine

38
Q

What are the side effects of 10% phenylephrine?

A

Stroke, MI, Cardiac arrest.

39
Q
A

PART ONE REVISION. (84 decks)

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