Pharmacology Flashcards
When is the topic route of administration used in eye diseases?
Required to act on surface
Require corneal penetration
What is the cornea made up from?
Lipophilic epithelium
Lipophobic stroma
What are the chemical properties of chloramphenicol?
Lipophilic and hydrophilic
What effect can ocular surface inflammation have on the nature of the endothelium?
Reduce the hydrophobic nature
Lipid layer of tear film may impede drug penetration
What are hydrophilic drugs limited by?
Epithelium
What are hydrophobic drugs limited by?
Stroma
How are steroids made more hydrophobic?
Addition of an alcohol or acetate
How are steroids made more hydrophilic?
Phosphate
When is prednisolone acetate used?
Good penetration in uninflamed cornea
Used post-op in cataract surgery
When is prednisolone phosphate used?
Poor penetration in uninflamed cornea
Used for cornea disease or when low dose steroids are wanted
What is benzalkonium?
Used as a surfactant and bacterial agent in prescription bottles to prevent growth of pseudomonas
What is the downside/ benefit of benzalkonium?
Disrupts lipid layer of tear film which can aid penetration of drugs but also can cause a dry eye
What is bimatoprost?
Drug used to lower IOP in glaucoma
How can topical eye drops by systemically absorbed?
Tears are pumped out of lacrimal sac and can be absorbed systemically at the nasopharynx
What can be done to prevent systemic absorption of topical drugs?
Punctal occlusion
How can injections in the eyes be given?
Subconjunctival
Subtenons
Intravitreal
Intracameral
What drops are commonly given for treatment of infections?
Chloramphenicol in the drop and ointment form
Aciclovir
Ofloxacin
How is ocular inflammation treated?
Dexamethasone drops Prednisolone drops Topical NSAIDs Anti-histamines Mast cell stabilisers
When are ocular steroids used?
Post op cataracts
Uveitis
Prevention of corneal graft rejection
What are the local ocular side effects of steroids?
Cataract
Glaucoma
Exacerbation of herpes simplex conjunctivitis - corneal melt
What are the systemic side effects of steroids?
Gastric ulceration - prescribe with proton pump inhibitor Immunosuppression Osteoporosis Weight gain Diabetes Neuropsychiatric effects
What is glaucoma?
A group of diseases characterised by a progressive optic neuropathy resulting in characteristic field defects
Raised IOP only modifiable risk factor
What can be seen on the optic disc in glaucoma?
Cupping
What meridian line will glaucoma tend to respect?
The horizontal line - affects the superior or inferior fields
What glaucoma drugs will work to open the trabecular meshwork/ canal of schlemm?
Prostanoids e.g. latanoprost
Alpha adrenergic agonists e.g. brimonidine
Parasympathomimetic e.g. pilocarpine
What glaucoma drugs will work to reduce the production of aqueous humor?
Beta blockers e.g. timolol
Carbonic anhydrase inhibitors e.g. dorzolamide
Alpha adrenergic agonists e.g. brimonidine
What are the advantages to intravitreal injections?
Delivers effective concentration of drug at target site but many drugs are toxic to the retina
Used as a method of administration of antibiotics in endophthalmitis
Intra-ocular steroids
Anti-VEGF in wet ARMG
What can be seen in endophthalmitis?
Hypopyon - pus fluid level in eye
Surgical complication
What are common diagnostic drops?
Proxymetacaine hydrochloride
Fluorescein
What are common dilating drops used?
Tropicamide
Phenylephrine
Atropine
Cyclopentolate
How do local anaesthetic drops work?
Blocks sodium channel to impede nerve conduction
When are local anaesthetic drops used?
FB removal Tonometry (IOP measurement) Corneal scraping Comfort Cataract surgery
When are fluorescein drops used?
Corneal abrasion Dendritic ulcer (herpes simplex keratitis) Identify leaks - seidel's test Tonometry Diagnose nasolacrimal duct obstruction Angiography
How do mydriatics (tropicamide, cyclopentolate) work?
Cause pupil dilation by blocking parasympathetic supply to iris
Cause cycloplegia
What are the symptoms of acute angle closure glaucoma?
High pressure in eye Acute red eye High pain N+V Headache Dilated pupil that is not reactive
How do sympathomimetics (atropine and phenylephrine) work to dilate the eye?
Acts on symp system to cause dilation
Atropine will cause cycloplegia
What is cycloplegia?
Can’t accomodate
What is the max effect and recovery from atropine drops?
Max effect: 30-40 mins
Recovery: 7-9 days
What is the max effect and recovery from cyclopentolate?
Max effect: 30-60 mins
Recovery: 8 hours
What is the max effect and recovery from phenylephrine?
Max effect: 20-60 mins
Recovery: 6 days
What is the max effect and recovery from tropicamide?
Max effect: 20-40 mins
Recovery: 6hrs to 1 day
What TB drug can cause optic neuropathy?
Ethambutol
What drug can cause maculopathy?
Chloroquine - never see this now as only prescribe hydroxychloroquine
What can amiodarone cause in the eye?
Vortex keratopathy
