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Pharmacology > Eye (year 2) > Flashcards

Eye (year 2) Flashcards

1
Q

what do topical drugs have to cross to penetrate the eye?

A

cornea, conjunctiva, sclera

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2
Q

what are the advantages of topical administration?

A

specific
minimal side effects
easy
convenient

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3
Q

what are the advantages of systemic delivery?

A

better for posterior segment

easier in fractious animals

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4
Q

where may a drug be distributed when delivered topically to the eye?

A

into the eye
drain into lacrimal duct
enter systemic circulation through nasal mucosa/conjunctiva
fall off eye

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5
Q

why must a gap be left when administered two drops of different topical drugs to the eye?

A

eye can only hold half a drop so if both applied the efficacy will be reduced

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6
Q

what ways can topical ocular drugs be improved?

A

increase retention time

optimise ability to penetrate cornea

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7
Q

retention time of a drug depends on the formulation, name these from shortest to longest retention time

A 
solution
suspension
ointment
viscous gel
colloidal system
solid delivery
sub-conjunctival injection
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8
Q

what does corneal penetration of the drug depend on?

A

solubility

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9
Q

what does corneal epithelium have that limits paracellular absorption?

A

tight junction

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10
Q

what route do lipid soluble drugs take through tissue?

A

trancellular

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11
Q

what route do water soluble drugs take through tissue?

A

paracellular

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12
Q

what part of the eye do water soluble agents easily cross?

A

stroma

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13
Q

what part of the eye do lipid soluble agents easily cross?

A

epithelium

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14
Q

what does a drug need to penetrate the cornea?

A

both hydrophilic and lipophilic characteristics

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15
Q

what effects the water and lipid solubility of a dug?

A

its ionisation

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16
Q

ophthalmic drugs have what type of pH?

A

weak acids or bases so have both ionised and unionised forms

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17
Q

is the ionised portion of the drugs water or lipid soluble?

A

water

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18
Q

is the unionised portion of the drugs water or lipid soluble?

A

lipid

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19
Q

describe the ionisation as ocular drugs move through the cornea?

A

unionised form moves through corneal epithelium with ease, it then ionises due to the abundance of unionised drug allowing it to move through the stroma, it then becomes unionised again to pass through the endothelium

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20
Q

what clinical factor may increase the absorption of topical ocular drugs?

A

corneal ulcers mean increased penetration for water soluble drugs

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21
Q

how can large hydrophilic molecules be absorbed into the eye?

A

via conjunctiva and sclera as they permit more paracellular movement

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22
Q

where can drugs enter from the sclera?

A

posterior segment

ciliary body

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23
Q

how is much of the topically administered drug absorbed systemically?

A

via the nasolacrimal duct

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24
Q

do topical drugs that penetrate via a non-corneal route have higher levels in anterior uvea or aqueous humour?

A

anterior uvea as they don’t pass through the aqueous humour to reach it but instead go through the ciliary body

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25
Q

what does the blood:ocular barrier consist of?

A

blood:aqueous and blood:retinal barriers

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26
Q

what is the blood:aqeuous barrier?

A

barrier between the blood in the vessels of iris/ciliary body and aqueous humour

27
Q

what is the blood:retinal barrier?

A

barrier retinal pigment epithelium and the retinal capillary endothelium

28
Q

why may pupil size want/need to be altered?

A

dilate for fundic exam
relax ciliary body to relieve spasms
constrict to open drainage angle
diagnostic tool

29
Q

what is the term used for pupil dilation?

A

mydriasis

30
Q

what is the term used for pupil constriction?

A

miosis

31
Q

what is the term used to describe relaxation/paralysis of the ciliary body?

A

cycloplegia

32
Q

what is a two groups of drugs that cause mydriasis?

A

parasympatholytics

sympathomimetics

33
Q

what do parasympatholytics do to the eye?

A

relax the iris sphincter muscle to cause dilation

34
Q

what do sympathomimetics do to the eye?

A

contact the dilator muscle to cause pupil dilation

35
Q

name two parasympatholytics that cause mydriasis

A

atropine and tropicamide

36
Q

name a sympathomimetic that causes mydriasis

A

phenylephrine

37
Q

describe the pharmacokinetics of atropine?

A

slow onset but a very long duration of action

38
Q

when is tropicamide used and why?

A

during pupil dilation exam due to its rapid onset and short duration of action

39
Q

what are the three components of tear film?

A

lipid, aqueous and mucin

40
Q

name two drugs that stimulate tear production

A

ciclosporin and pilocarpine

41
Q

what is ciclosporin used for?

A

directly stimulate tear production and addresses underlying immune mediated cause as it is an immunosuppressant

42
Q

what type of drug is pilocarpine?

A

parasympathomimetic

43
Q

what are the categories tear substitutes fall into?

A

aqueous substitutes
mucin replacements
lipid replacements

44
Q

give an example of a mucin replacement

A

carbomer gel

45
Q

what type of acid is a good mucin replacer?

A

hyaluronic

46
Q

what are lipid replacements used for?

A

increase tear retention time

47
Q

what is glaucoma?

A

sustained increase in intraocular pressure

48
Q

what can glaucoma cause?

A

pain, blindness, irreversible structure changes

49
Q

what is glaucoma usually due to?

A

decreased aqueous humour outflow

50
Q

what are the aims of glaucoma treatment?

A

increase aqueous humour outflow
decrease aqueous humour production
both

51
Q

what drugs can be used in acute first line treatment of glaucoma?

A

osmotic diuretics

52
Q

what do osmotic diuretics require to work?

A

intact blood:ocular barrier

53
Q

how do osmotic diuretics work?

A

increase blood tonicity causing water to be drawn out of the aqueous humour

54
Q

name the groups of drugs that can be used to treat glaucoma

A

carbonic anhydrase inhibitors
prostaglandin analogues
beta blockers
parasympathomimetics

55
Q

how do carbonic anhydrase inhibitors work?

A

reduce the formation of bicarbonate in the ciliary body epithelium which reduces the blood drawn into the aqueous humour

56
Q

how are carbonic anhydrase inhibitors administered?

A

topically

57
Q

how do prostaglandin analogues work to treat glaucoma?

A

increase the outflow of aqueous humour by increasing uveoscleral outflow by altering the structure of the outflow tract

58
Q

prostaglandin analogues are thought to also preserve vision in glaucoma patients, how?

A

increase perfusion of optic nerve head by vasodilation

59
Q

what is an adverse effect of prostaglandin analogues?

A

can be irritants

60
Q

give an example of a beta blocker used to treat glaucoma

A

betaxolol - topical beta1 antagonist

61
Q

how do parasympatheticomimetics work to treat glaucoma patients?

A

contact ciliary body to constrict the pupil and open the drainage angle to increase the outflow of aqueous humour

62
Q

name a parasympatheticomimetics used to treat glaucoma

A

pilocarpine

63
Q

what do parasympatheticomimetics rely on to work in glaucoma patients?

A

an intact drainage angle

Pharmacology (25 decks)

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