Pharmacology

Question 1

Topical eye drugs may be required to work in two places? What are the two types of topical drugs?

Answer 1

1- on the surface of the eye
2- may require corneal penetration

Drops and ointment

Question 2

Describe the layers of the cornea and how this has to be considered in prescribing drugs?

Answer 2

lipid, water, lipid sandwich
The epithelium is lipophilic and the stroma in the middle is hydrophilic
So drugs that penetrate the cornea usually have both lipophilic and hydrophilic properties
Hydrophilic drugs limited by epithelium
Hydrophobic drugs limited by stroma

Question 3

Ocular surface inflammation can often ________ the hydrophobic nature of the endothelium

Answer 3

reduce

Question 4

How are topical steroids for the eye altered to allow penetration?

Answer 4

Alcohol or acetate makes steroid more hydrophobic

Phosphate makes it more hydrophilic

Question 5

Describe the difference between prednisolone acetate and prednisolone phosphate?

Answer 5

Prednisolone acetate
hydrophobic
Good penetration in uninflamed cornea
Used post-operatively

Prednisolone phosphate
hydrophilic
Poor penetration in uninflamed cornea
Used for cornea disease or when want low dose steroids

Question 6

Describe the role of benzalkonium in eye drops?

Answer 6

Benzalkonium is a preservative.
Also disrupts lipid layer of tear film
Aids penetration of some drugs

Question 7

Describe how you can get systemic absorption of some topical drugs and how this can be limited?

Answer 7

Tears are pumped out of lacrimal sac rapidly
Excess gains systemic absorption at nasopharynx
Limited by punctal occlusion

Question 8

Describe the role of 3 diagnostic drops?

Answer 8

• Local Anaesthetics used for measuring pressure, FB removal, corneal scraping, comfort and cataract surgery
• Fluorescein- shows corneal abrasions, shows dendritic ulcers, identify leaks by dilution of the fluoroscein, diagnose nasolacrimal duct obstruction by visualising where tears go, can also be used in angiography
Mydriatics- act on sympathetics or block sympathetics to dilate pupil allowing better view into the eye

Question 9

Ethambutol is used in what condition? Effect on eye?

Answer 9

Used in Tb

Damage sight

Question 10

Digoxin is used in what condition? Effect on eye?

Answer 10

Heart problems, heart failure

Disruption of colour vision

Question 11

Chlroquinine and hydroxyquinine are used in? Effect on eye?

Answer 11

Chloroquine for malaria causes maculopathy > hydroxychloroquinine can also cause maculopathy but not as bad (new drug)
Sometimes used in autoimmune diseases

Question 12

Amiodarone effect on the eye? When is amiodarone used?

Answer 12

Arrhythmias

cause black brown pigmentation in front bit of cornea which can be seen on slit lamp