Pharmacology Flashcards
What is the corneas composition?
lipid:water:lipid
What is the compostition of the epithelium?
lipophilic and hydrophobic
What types of drugs penetrate the epithelium of the cornea?
hydrophobic drugs - lipid soluble
What types of drugs penetrate the stroma of the cornea?
hydrophillic drugs - water soluble
What is the compostition of the stroma?
lipophillic and hyodrphillic
What type of substance can get through the tear film of the cornea?
lipophilic
What type of drug is chloramphenicol?
lipophillic and hydrophilic so penetrates the corena easily
What does inflammation do to corneal penetration?
makes it easier as it reduces the hydrophobicness
What is the compostion of topical steroids?
hydrophobic and hydrophilic
What happens to a drug if it cannot go through the tear film?
it’ll get washed out
How do you make a steroid more hydrophobic?
add an alcohol or acetate
How do you make a steroid more hydrophilic?
add a phosphate
When is prednisolone acetate used? What are its properties?
post op
hydrophobic - good for penetration of an uninflammed cornea
When is prednisolone phosphate used? What are its properties?
used for corneal disease or low dose steroid use
hydrophilic - good penetration of an inflammed cornea
What is the most common pathogens for eye infections with contact lenses?
pseudomonas
What is pseudomonas infection treated with?
Benzalkum chloride - punches out holes in the walls of bacteria but has bad side effects so now use
Bimatoprost 0.1% - benzalkum chloride content of 0.2%
What is the side effect of Benzalkum chloride?
strips out a layer of cornea
How can you increase topical drug absorption in the eye?
punctal occlusion
How can occular injections be done?
either intravitreal or intracameral
What happens if antibiotics are injected into the wrong place?
retinal detachment
What should steroids NEVER be given to?
Herpes Keratitis
When should steroids be used?
post op cataracts - can also cause cataracts tho uveitis preventing corneal graft rejection temporal arteritis anterior ischeamic neuropathy
What are the local side effects of steroids?
cataracts - reversible
glaucoma
exacerbation of viral infection
What are the systemic side effects of steroids?
gastric ulceration immunosuppression osteoporosis weight gain diabetes neuropyschiatric effects
When are NSAIDs used?
pain relief post refractive laser
cataracts
When are antihistamines and mast cell stabalisers used?
hay fever
conjunctivitis
What is the aim of glaucoma medication?
unblock the trabecular meshwork or reduce production of aqueous
What medications unblock the trabecular meshwork in glaucoma?
prostanoids - latansoprost
alpha-2-adrenergic agonist - brimomidine
What medications are used to reduce the production of aqueous humour in glaucoma?
beta blockers - trimolol
carbonic anhydrase inhibitors = dorzolamide
alpha-2-adrenergic agonists = brimomidine
Why can some systemic drugs not enter the eye?
blood - retinal barrier
What is endopthalmitis?
white cells in the eye due to surgery
sight threatening
How is endopthalmitis treated?
antibiotics intravitreally
How do eye local anaesthetics work?
block sodium channels and impede nerve conduction
When are local anaesthetics used?
forgein body removal tonometry - ICP measurement corneal scraping comfort cataract surgery
What is the role of mydriatic drugs?
blocks parasympathetic supply to iris causing dilation
also causes cycloplegia - stops the lens focussing
What are the side effects of mydriatic drugs?
blurring
What are the role of sympathomimetics?
acts on sympathetic system to enhance sympathetics
some cause cycloplegia - stops the lens focussing (atropine)
some do not - phenylephrine
