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CNS > Ocular pharmacology > Flashcards

Ocular pharmacology Flashcards

1
Q

How can drugs be administered for ocular purposes

A

Topical

Systemic

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2
Q

What are the advantages of topical administration?

A

Convenient
Sometimes easy?
Minimal systemic side effects

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3
Q

Topical drugs are distributed in the eye in 3 ways. What are these?

A

Drainage by lacrimal drainage system
Penetration of eye via cornea/sclera
Through conjunction and nasal mucosal vessels

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4
Q

When topical drugs are distributed via nasal/conjunctival mucosa, were do they go? What is the efficacy of this?

A

Systemic circulation

Like slow IV

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5
Q

What are the disadvantanges of topical administration?

A

Drops are bigger volume than palpebral fissure can hold - excess spills out
15% tear film turned over/min - rapidly removed from surface
Poor bioavailability - only fraction of drug reaches anterior chamber

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6
Q

How can the bioavailability of topical drugs be improved in the eye?

A

Increase drug retention on palpebral fissure

Increase ability to penetrate cornea

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7
Q

What type of topical treatments can be applied to the eye?

A 
Solution
Suspension 
Ointment
Viscous fluid/gel
Colloidal system 
Subconjunctival injection
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8
Q

What is it called when drugs bind to tear film? What conditions is this suitable for?

A 
Bioadhesion 
Dry eye (keratoconjunctivitis sicca)
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9
Q

Why is corneal penetration and absorption of ocular drugs limited?

A

Tight junctions in corneal epithelium - limit paracellular absorption

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10
Q

Topical corneal drugs can be lipid soluble or water soluble (should be both!). What parts of the cornea do they cross?

A

Lipid soluble -cross epithelium

Water soluble - cross stroma

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11
Q

When drugs penetrate the cornea, what structures of the eye do they go to? Which structures receive low levels of corneally absorbed drugs?

A

Aqueous humor, iris, ciliary body

Lens, vitreous humor and posterior segment receive little of drug

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12
Q

Non-corneal penetrative drugs enter the eyeball via the conjunctiva and sclera.. Are theses drugs hydrophilic or lipophilic?

A

Hydrophilic

Conjunctiva epithelum and sclera more permeable corneal epithelium

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13
Q

When drugs enter the eye via the sclera, where do they go?

A

Posterior segment or scleral vessels and ciliary body

Drug level higher in anterior uvea than aqueous

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14
Q

Where are topical ocular drugs metabolised?

A

In corneal epithelium

Or target tissue

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15
Q

Systemic ocular drugs are better for when trying to target what segment of the eye? What are the other advantages?

A

Posterior

Easier administration?

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16
Q

What is the blood ocular barrier (BOB)? What does it consist of?

A

Barrier between eye and blood stream
BAB - blood:aqueous barrier
BRB - blood:retinal barrier

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17
Q

The BOB affects the ability of many drugs to penetrate the eye. Which section of the BOB (BRB or BAB) sis leakier?

A

Blood:aqueous barrier leakier - allows agents to easily cross into anterior segment

18
Q

Do lipophilic or hydrophilic drugs penetrate the BOB easier?

A

Lipophilic

19
Q

What is the word for pupil dilation? What about constriction?

A

Mydriasis - relaxation

Miosis - constrinction

20
Q

What type of drugs cause pupil dilation? (mydriasis)

A

Parasympatholytics - release iris sphincter

Sympathomimetics - contract the dilator muscle

21
Q

Why may you want to cause pupil dilation? (mydriasis)

A

Eye exam

Contract ciliary body muscles to relieve painful spasms

22
Q

What is the word for relaxation/paralysis of the ciliary muscle?

A

Cycloplegia

23
Q

What innervates the pupil dilator muscle?

A

Sympathetic innervation

Nasociliary nerve

24
Q

What innervates the pupil constrictor muscle?

A

Parasympathetic innervation

Occulomotor nerve

25
Q

What drugs can be used for pupil dilation?

A

Atropine
Tropicamide
Phenylnephrine

26
Q

What are the disadvantages/advantages of atropine?

A

Slow onset
Long duration
Causes systemic antimuscarinic effects - problem in horse (Colic)

27
Q

Atropine causes mydriasis. Is it a sympathomimetic or parasympatholytic?

A

Parasympatholytic

28
Q

Tear film maintains the health and clarity of the cornea. What do conditions like dry eye require as part of their treatment? Give an example

A

Tear substitutes

Pilocarpine

29
Q

How does pilocarpine work? When might it be given?

A

Actively increases tear production, parasympathomimetic

Dry eye, during GA to prevent eyes drying out

30
Q

What are the 3 categories of tear substitutes?

A

Aqueous substitutes
Mucin layer mimics
Drugs that replace the lipid portion of the tear film

31
Q

Why are aqueous substitutes of tear films limited?

A

Lost quickly from ocular surface

Need frequent application

32
Q

What is glaucoma? What does it cause?

A

Oedema of eye

Intraocular pressure damages optic nerve - pain blindness, irreversible structural changes

33
Q

What can cause an increased intraocular pressure (leading to glaucoma)?

A

Decreased aqueous outflow

34
Q

Glaucoma drugs include emergency treatment and drugs for management. What is the first line of Tx for emergency intervention? Give an example

A

Osmotic diuretics

Mannitol

35
Q

How do osmotic diuretics work to treat glaucoma? What do they rely on being intact? Why are they for short term, emergency use only?

A

Increase in blood tonicity causes water to be drawn out of aqueous and vitreous humor
Intact BOB
Cannot be long term –> hypovolaemia

36
Q

What drugs can be used to maintain glaucoma treatment?

A

Carbonic anhydrase inhibitors
Prostaglandin analogues
Beta blockers
Parasympathomimetic drugs

37
Q

How do carbonic anhydrase inhibitors work to treat glaucoma? Give an example

A

Carbonic anhydrase ataylses hydration of CO2 to HCO3 and H+. HCO3 draws water into aqueous
Inhibition of this - stops water being drawn into aqueous
Brinzolamide

38
Q

How do prostaglandin analogues work to treat glaucoma? Give an example

A

Increase uveoscleral outflow of aqueous

Latanoprost

39
Q

How do beta blockers work? Give an example of a topical agent used

A

Reduce aqueous formation

Betaxolol

40
Q

How do parasympathomimetic drugs work to treat glaucoma? Give an example

A

Contract ciliary body and constrict pupil
Widens drainage angle - increases aqueous outflow
Pilocarpine

CNS (15 decks)

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