Pharmacology

Question 1

What must a topical drug be able to do?

Answer 1

Act on the surface and penetrate the cornea

Question 2

Describe the structure of the cornea in terms of solubility

Answer 2

Consists of two lipophilic epithelium with hydrophilic stroma in between

Question 3

Name a drug that is both lipid and water soluble

Answer 3

Chloramphenicol

Question 4

What is the consequence of ocular inflammation on solubility?

Answer 4

Reduces the hydrophobic nature of the epithelium

Question 5

How are steroids made more hydrophobic?

Answer 5

Add alcohol or acetate (prednisolone acetate)

Question 6

How are steroids made more hydrophilic?

Answer 6

Add phosphate (prednisolone phosphate)

Question 7

Describe predisolone acetate

Answer 7

Hydrophobic, allows good penetration in an uninflammed cornea and is used post-op

Question 8

Describe prednisolone phosphate

Answer 8

Hydrophilic, has poor penetration in an uninflammed cornea but is used in corneal disease where low doses are required

Question 9

What chemical can be added to drugs to aid penetration?

Answer 9

Benzalkonium Chloride

Question 10

Other than aiding penetration what else does benzalkonium chloride do?

Answer 10

It is a preservative emollient that depletes the lipid tear film and kills some microbes

Question 11

What are the side effects of benzalkonium chloride?

Answer 11

Some patients are allergic and some experience dry eyes

Question 12

How does systemic absorption of topical drugs occur?

Answer 12

Excess tears go through the nasopharynx and can enter the GI tract

Question 13

What advice can be given to patients experiencing GI side effects of topical drugs?

Answer 13

Occlude the puncta to limit systemic absorption

Question 14

Name four other routes of administration (apart from topical)

Answer 14

• subconjunctival (acts like a deposit)
• subtenous (into posterior orbital space)
• intravitreal injection
• intracameral injection

Question 15

What drugs are often given subconjunctivally?

Answer 15

Steroids and antibiotics

Question 16

Name four drugs given to patients with ocular inflammation

Answer 16

• Steroids
• NSAIDs
• Anti-histamines
• Mast cell stabilisers

Question 17

How do steroids work?

Answer 17

Suppress the immune inflammatory response

Question 18

When are steroids used?

Answer 18

Post op cataracts
Uveitis
Prevent corneal graft rejection
Temporal arterities

Question 19

What are the signs of uveitis?

Answer 19

Circumcorneal injection - enlargement of ciliary and conjunctival vessels
Keratic precipitates
Yellow/white dots in chorioretinitis with ischaemia

Question 20

Why are steroids used in temporal arterities?

Answer 20

IV steroids are used as it can cause optic nerve infarction, anterior ischaemic neuropathy and blindness

Question 21

What are the ocular side effects of steroids?

Answer 21

Cataract
Glaucoma
Exacerbation of virus

Question 22

What is the only clinically modifiable risk factor for glaucoma?

Answer 22

Raised intraocular pressure

Question 23

What kind of vision do patients with glaucoma have?

Answer 23

Tunnel vision

Question 24

What does the treatment of glaucoma aim to do?

Answer 24

Slow the disease down and prevent loss of vision

Question 25

Name five medications used in glaucoma

Answer 25

- prostanoids - beta blockers - carbonic anhydrase inhibitors - alpha 2 adrenergic agonists - parasympathomimetics

Question 26

What is the mechanism of action of prostanoids?

Answer 26

Open the drain

Question 27

What is the mechanism of action of beta blockers?

Answer 27

Turns off the tap

Question 28

What is the mechanism of action of carbonic anhydrase inhibitors and how can they be administered?

Answer 28

Turn off the tap can be given orally or IV in an acute situation

Question 29

How do alpha 2 adrenergic agonists work?

Answer 29

Turn off the tap and open the drain by vasodilation

Question 30

How do parasympathomimetics work?

Answer 30

Open the drain by pulling on the iris

Question 31

What drugs are absolutely contraindicated in children?

Answer 31

Alpha 2 agonists due to fatigue and sleep apnoea, they can also cause an allergic reaction

Question 32

Describe intravitreal administration

Answer 32

Delivers effective concentrations of drug at site but they may be toxic to the retina

Question 33

When are intravitreal drugs given?

Answer 33

Antibiotics in endophthalmitis | Steroids and anti-VEGF in wet ARMD

Question 34

What is the mechanism of action of local anaesthetic?

Answer 34

Blocks sodium channels and impedes nerve conduction

Question 35

When is local anaesthetic used?

Answer 35

``` Foreign body removal Tonometry Corneal scraping Comfort Cataract surgery ```

Question 36

What does tonometry do?

Answer 36

Measure intra-ocular pressure

Question 37

What is the most common diagnostic dye?

Answer 37

Fluorescein

Question 38

What are diagnostic dyes used for?

Answer 38

Corneal abrasion, dendritic ulcer, identifying leaks, tonometry, nasolacrimal duct obstruction and angiography

Question 39

What do some mydriatics do to the ciliary muscles?

Answer 39

Paralyse them

Question 40

When are parasympathomimetics used?

Answer 40

To decrease pressure

Question 41

What TB drug can cause ocular side effects?

Answer 41

Ethambutol - optic neuropathy

Question 42

What ocular side effect can hydroxychloroquine cause?

Answer 42

Bulls Eye Maculopathy

Question 43

Which heart drug can cause disturbance to colour vision?

Answer 43

Digoxin

Question 44

When must steroids never be given?

Answer 44

Hepatic Keratitis