Pharmacology Flashcards
routes of drug administration for the eye?
topical
subconjunctival
subtenosis (under conjunctiva)
ocular injections e.g. intravitreal and intracameral (anterior chamber)
two layers in the cornea
lipid
water layer
chemical properties of the epithelium in the cornea
lipophilic/hydrophobic
chemical properties of the stroma in the cornea
lipophobic/hydrophilic
what parts of the cornea can lipid soluble drugs penetrate?
epithelium
what parts of the cornea can water-soluble drugs penetrate?
stroma
example of a drug that can penetrate both the epithelium and stroma
chloramphenicol
what can ocular surface inflammation cause?
reduce hydrophobia of epithelium
what drugs are limited by epithelium
hydrophilic
what drugs are limited by stroma
hydrophobic
examples of modifiers added to topical steroids to change characteristics
alcohol or acetate
phosphate
what does alcohol and acetate do when added to topical steroids?
makes steroids more hydrophobic
what does phosphate do when added to topical steroids
makes steroids more hydrophilic
examples of steroids used in the eye
- prednisolone acetate= hydrophobic
- prednisolone phosphate= hydrophilic
what is benzalkonium chloride
antibacterial agent and preservative that can disrupt the lipid layer of the tear film aiding drug penetration
what is benzalkonium chloride added to?
bimatoprost
what happens if the dose of benzalkonium chloride is too high?
topical side effects/ allergic reaction with reddening around the eye
how can topical drugs be absorbed systemically
tears pumped out of lacrimal sac
systemic absorption at nasopharynx
limited by punctal occlusion (for 5 minutes after administration)
examples of anti-inflammatory agents
steroids
topical NSAIDs
antihistamines
mast cell stabilisers
when are steroids used?
post-op cataracts (expose self-proteins in the eye to central immune system)
uveitis
prevention of corneal graft rejection (risk of new vessel formation)
example of a condition when steroids are immediately needed?
temporal arteritis
local side effects of steroids
cataracts
glaucoma
exacerbation of viral infections
systemic side effects of steroids
gastric ulcer immunosuppression osteoporosis weight gain diabetes neuropsychiatric effects overall reduced life expectancy
when should you never give steroids alone?
hepatic keratitis as needs antiviral cover (dendritic ulcer)
glaucoma medication categories
- prostanoid
- beta blockers
- carbonic anhydrase
- alpha2-adrenergic agonists
- parasympathomimetic
example of prostanoid
latanoprost
why are beta blockers used in glaucoma?
inhibit enzyme responsible for producing aqueous
examples of beta blockers given in glaucoma
timolol
bextaxolol
levobunolol
carteolol
examples of carbonic anhydrase inhibitors
topical dorzolamide
systemic acetazolamide
role of alpha2-adrenergic agonists
vasodilators
side effect of brimonidine (alpha2-adrenergic agonist)
overwhelming fatigue
example of parasympathomimetic
pilocarpine
why is compliance an issue
side effects include red eye, dry, odd taste, stings, etc.
when are intravitreal injections used?
administering antibiotics (endophthalmitis) intra-ocular steroids (diabetic retinopathy, retinal vein occlusion and uveitis) anti-VEGF (wet ARMD, diabetic retinopathy and retinal vein occlusion)
when is local anaesthetic used in the eye?
foreign body removal
tonometry (IOP measure)
corneal scraping
cataracts
what does local anaesthetic have a risk of?
corneal melt
how does local anaesthetic impede nerve conduction?
blocks Na+ channels
when is the diagnostic dye fluorescein used?
corneal abrasion dendritic ulcers identify leaks tonometry nasolacrimal duct obstruction angiography
examples of mydriatics
tropicamide
cyclopentolate
action of mydriatics
cause pupil dilation by blocking parasympathetic supply to iris causes cycloplegia (stops lens from focusing)
side effects of mydriatics
blurring
AACG
action of sympathomimetics
cause the pupil to dilate by acting on the sympathetic system (some cause cycloplegia e.g. atropine) and some do not e.g. phenylephrine
ocular side effect of vigabatrin
constricts fields
ocular side effects of ethambutol
optic nerve stops functioning and appears pale
ocular side effect of digoxin
affects ability to judge colour
ocular side effect of chloroquine
maculopathy- screening
ocular side effect of amiodarone
brown pigmentation at the cornea
