Pharmacology Flashcards
What is the main route of administration of drugs into the eye?
Topical :
either Drops OR Ointment
Describe the makeup of the cornea and therefore what drugs are best at penetrating this barrier
Lipid:Water:Lipid
=> Low molecular weight drugs easily cross the barrier
What type of drugs penetrate the epithelium vs the stroma?
Lipid soluble drugs penetrate epithelium
Water soluble drugs penetrate stroma
If a drug is lipoPHOBIC (i.e dissolves in water) will it reach into the eye?
No it will dissolve in the tear film and be washed away
If a drug is hydroPHOBIC (i.e dissolves in lipid) will it reach into the eye?
It will take a while to get through the stroma (as this is water soluble) but a high enough concentration will be present for the drug to eventually get to the back of the eye
Give an example of an eye drop which possesses both hydrophilic and lipophilic properties
Chloramphenicol
How are topical steroids made to be more hydrophobic?
Alcohol or acetate = added
=> easier to dissolve in lipid
How can a topical steroid become more hydrophilic?
Phosphate added
=> dissolves more easily in water
What topical steroid is used in the eyes?
Prednisolone
What steroid is used after a cataracts operation?
Prednisolone acetate
What steroid is used in conjunctival inflammation?
Prednisolone Phosphate (as it only need to reach surface)
What chemical is found in eye drop preparations to prevent organisms growing in the bottles?
Benzalkonium Chloride
What effect does Benzalkonium Chloride have on the cornea?
strips away the lipid layer
How can topical drugs be systemically absorbed?
Tears = pumped out of lacrimal sac rapidly
Excess is absorbed at nasopharynx
(hence bad taste at back of throat)
How can systemic absorption be minimised?
Limited by punctal occlusion
pressing fingers on nasal part of lacrimal apparatus
What is the side effect of high dose Bimatoprost (0.03%) that contains low Benzalkonium Chloride?
Red/Black staining around the eye
Give an example of drops that can cause systemic side effects?
Beta Blocker drops (e.g. Timolol)
When would a subconjunctival injection be used?
Very inflamed uveitis
Where in the eye is a subtenon injection?
Into back of the orbit
What part of the eye is spared in an intravitreal injection?
Retina
An intracameral injection is put into where?
The anterior part of the eye
What anti-inflammatory agents are used in the eye?
Steroids
Topical NSAIDs
Anti-histamines
Mast cell stabilisers
When are steroid most commonly used in the eye?
1) post op cataracts
2) uveitis
3) prevent corneal graft rejection
What can be seen if a corneal graft is being rejected?
vascularisation of the cornea
How does temporal arteritis usually present?
- Sudden temporal pain
- Older patients
- Multi-nucleated giant cells seen on artery biopsy
What structure is affected in Anterior Ischaemic Neuropathy?
Optic nerve infarct
What are the local eye side effects of steroids?
cataract
glaucoma
exacerbation of viral infection
What are the systemic side effects of steroids in the eye?
- Gastric ulceration
- Immunosuppression
- Osteoporosis
- Weight gain
- Diabetes
- Neuropsychiatric effects
Give examples of steroid eye drops from lowest to highest strength
- Fluorometholone (FML)
- Predsol
- Betamethasone
- Dexamethasone/ prednisolone
What type of analgesia is used after refractive laser treatment
NSAIDs
What word is used to describe the vision of patients with glaucoma?
Tunnel vision
What types of eye drops can be used in glaucoma?
Prostaglandins Beta blockers Carbonic anhydrase inhibitors (Topical or Systemic) Alpha-2 adrenergic agonist Parasympathomimetic drops
Give an example of a prostaglandin eye drop used in glaucoma
Latanoprost
Give an example of a topical and systemic carbonic anhydrase inhibitor
Topical = Dorzolamide (‘Trusopt’) Systemic = acetazolamide
Give an example of a Beta Blocker used in glaucoma
Timolol
GIve an example of an Alpha-2 Agonist drop used in glaucoma
Brimonidine (‘Alphagan’)
Give an example of a Parasympathomimetic eye drop used in glaucoma
pilocarpine
Give an example of eye drops which come in combination specifically for glaucoma
Cosopt = dorzolamide and timolol
When is Anti-VEGF given via intravitreal injection?
Wet macular degeneration
What eye drops are used for diagnosis?
Proxymetacaine
Fluorescein
What drops are usually used for dilation?
Tropicamide
Phenylephrine
When are local anaesthetics used?
1) Foreign Body removal
2) Tonometry (IOP measurement)
3) corneal scraping
4) comfort
What can fluorescein dye be used for?
1) Identifying Corneal abrasion
2) Tonometry
3) Diagnosing Nasolacrimal duct obstruction
4) Angiography
How do mydriatic drops cause dilatation?
pupil dilation by blocking parasympathetic supply to iris
What are sympathomimetics?
- Act on sympathetic system
- Causes pupil to dilate
- Do not affect the ciliary muscle
Give examples of sympathomimetics
Phenylephrine
Atropine
Give an example of a medication for another condition which can irreversibly constrict the visual field
Vigabatrin - epilepsy medication (anticonvulsant)
If tropicamide does not dilate the eye enough, what should be added and what should the patient be warned?
Phenylephrine added
Tell patient it will probably take about 24hrs to wear off (rather than original tropicamide which would take less time)
How can you tell a patient has definitely developed an allergy to their eye drop?
Reaction is symmetrical in both eyes
Hydroxychloroquine is known to cause maculopathy. TRUE/FALSE?
TRUE
but only at accumulative doses
What drug can cause vortex keratinopathy and how does it appear?
Amiodarone
Brown pigment visible in epithelium
