Pharmacology Flashcards
how do topical agents work?
can act on the surface
can penetrate the cornea
2 types of topical agent?
drops
ointment
describe the layers of the cornea
lipid:water:lipid sandwich
90% of the cornea is water
how does the structure of the cornea relate to cornea penetrating drugs?
epithelium is lipophilic/hydrophobic and stroma is lipophobic and hydrophilic
therefore
to penetrate epithelium, drug must be lipid soluble
to penetrate stroma, drug must be water soluble
give an example of a type of drug which penetrates cornea?
LMW drugs
chloramphenicol has lipophilic and hydrophilic properties to can penetrate
what can influence drug penetration in the cornea?
ocular surface inflammation (can reduce hydrophobic nature of endothelium)
lipid layer of tear film can impede penetration
hydrophillic drugs limited by epithelium
hydrophobic drugs limited by stroma
what area of the eye limits absorption of hydrophilic drugs?
epithelium
what are of the eye limits absorption of hydrophobic drugs?
stroma
describe the features of prednisolone acetate?
hydrophobic
good penetration of uninflamed cornea
used post op in cataract surgeery
what are the features of prednisolone phosphate?
hydrophilic
poor penetration in uninflamed cornea
used for cornea disease or when want low dose steroid
more used in surface inflammation
what is benzylkonium?
type of ammonia which destroys bacteria which can culture in eye drops
keeps bottle of drops sterile
how does benzalkonium work?
disrupts lipid layer of tera film
aids penetration of some drugs
give an example of a glaucoma drug and 2 side effects?
bimatoprost
lack of benzalkonium can cause red eyes and darkening around eyes
how are topical drugs systemically absorbed?
tears are pumped out of lacrimal sac rapidly
excess gains systemic absorption at nasopharynx
limited by punctal occlusion
give 2 non-topical routes of administration
subconjunctival
subtenons
give 2 types of ocular injection
intravitreal (into the back of the eye)
intracameral (into the front of the eye)
name 4 anti-inflammatory agents used in the eye
steroids
topical NSAIDs
anti-histamines
mast cell stabilisers
what do steroids do and what 3 conditions are the used in?
suppress inflammation, allergy and immune response used topically in - post op cataract - uveitis - to prevent corneal graft rejection
what can indicate a corneal graft rejection?
vessels approaching the cornea
vision blurred
white line appears in the cornea
how does temporal arteritis relate to the eye?
can cause vague visual symptoms
can lead to blindness
how is temporal arteritis managed?
systemic steroids
non-pressure related cause of optic disc swelling?
anterior ischaemic neuropathy
loss of blood supply to the optic nerve
name 3 local side effects of steroids
cataract
glaucoma
exacerbation of viral infection
name 6 systemic side effects of steroids?
gastric ulcer immunosuppression osteoporosis weight gain (moon face) diabetes neuropsychiatric effects
4 strengths of steroid?
FML (weak)
Predsol (prednisolone phosphate) = moderate
betamethasone = potent
dexamethasone/prednisolone acetate = very potent
when might NSAIDs be used in the eye?
can be used for pain relief in post laser eye surgery or in conreal abrasion (in place of local anaesthetic which can reduce healing)
what is glaucoma?
group of dieases characterised by progressive optic neuropathy resulting in characteristic field defects
what is the only modifiable risk factor in glaucoma?
raised intra-ocular pressure
features of glaucoma?
usually asymptomatic unless in late stage
chronic disease
usually slowly progressive
how does the optic disc change in glaucoma?
cup increases in size as the number of nerve fibres surrounding the cup decreases so it occupies the space
can impact vessels
characteristic visual field of glaucoma?
tunnel vision
brain only sees central vision but brain fills in the periphery with what it thinks is there
how do glaucoma drops work?
either close the tap or open the drain for aqueous humor
name 5 common glaucoma medications
prostanoids (latanoprost/xalatan) = most common
beta blockers
carbonic anhydrase inhibitors (“…zolamide”)
alpha2 adrenergic agonist (brimonidine/alphagan)
parasympathomimetic (Pilocarpine)
how does intravitreal administration work?
delivers effective concentration of drug at target site instantly
but many drugs are toxic to retina
what is intravitreal administration for?
used as method of administration of antibiotics in endopthalmitis
used to deliver intra-ocular steroids
anti VEGF delivery
sign of endopthalmitis?
hypopyon
how does local anaesthetic work?
blocks sodium channels and impedes nerve conduction
name 5 uses for local anaesthetic in the eye
FB removal tonometry (IOP measurement) corneal scraping comfort cataract surgery
what is the most commonly used diagnostic dye and in what 6 cases may it be used?
fluorescein
- shows corneal abrasion
- dendritic ulcer
- indentify leaks
- tonometry
- diagnosing nasolacrimal duct obstruction
- angiography
what are mydriatics?
cause pupil dilation by blocking parasympathetic supply to the iris
e. g
- tropicamide
- cyclopentolate
name 2 side effects of mydriatics
blurring (cycloplegia) - stop the lens from focusing
AACG
signs of acute angle closure glaucoma?
sudden onset headache
vomiting
pupil mid-dilated
red sclera
what are sympathomimetics?
another class of pupil dilators
how do sympathomimetics work and name a side effect
acts on sympathetic system
causes pupil to dilate
some can cause cycloplegia (e.g atropine)
some don’t cause cycloplegia (phenylephrine)
in what condition must steroid never be given?
herpetic keratitis
name a drug which can cause irreversible constriction of visual fields?
vigabatrin (anti convulsant)
name a drug which can cause cataract
steroids
name a drug which can cause optic neuropathy
ethambutol (for TB)
name a drug which can cause maculopathy
chloroquine (hydroxychloroquine can cause if an accumulated dose)
what drug can cause vortex keratopathy?
amiodarone
