Week 2.06 Glaucoma Medications Flashcards
What’s the main aim of glaucoma medications
To reduce IOP
How can we reduce iop
1) Inhibition of aqueous humour production
a) regulated by sympathetic nervous system
2) increase/promote aqueous humour outflow
Ciliary body site of aqueous humour production
The ideal glaucoma medication
Ease of use
Satisfactory reduction in IOP
No ocular or systemic side effects
Consistent efficacy
What is the most commonly prescribed first line med for POAG
Prostaglandin analogues
Mode of action: promote drainage of aqueous humour via uveal-scleral pathway
Uveoscleral outflow: reabsorption of aqueous humour through the ciliary muscle is increased by muscle relaxation and facilitated by prostaglandins
When is the highest iop
First thing in the morning so we watch to match peak drug effect with peak in IOP
What are 4 different prostaglandin analogues
Latanoprost - first one available, preserved
Travoprost - newer than latanoprost, not preserved with Benzalkonium chloride
Bimatoprost - provides a larger reduction in IOP, preserved
Tafluprost - preservative free prostaglandin
What are the side effects of prostaglandin analogues
- Irritation and conj hyperaemia
- Punctate epithelial erosions
- Iris hyperpigmentation - irreversible
- Eyelash thickening, darkening, lengthening
- Darkening of peri-ocular skin
What are beta blockers
Receptors of sympathetic system
Mode of action: inhibiting production of aqueous humour by blocking beta receptors known as ‘antagonist’ action
If beta receptors blocked, norepinephrine cannot stimulate receptor therefore cannot increase production
When would you use beta blocker instead of prostaglandin analogue
- when px at risk of side effects of PA
- monocular treatment
- previous uveitis or keratitis
Efficacy = 20-30% lower than prostaglandin
What are two examples of beta blockers
Timolol
Levobunolol
What are the ocular side effects to beta blockers
Dry eye - reduced aqueous production
Punctate epithelial erosions- due to preservative
Hypersensitivity - Benzalkonium chloride
Adrenergic antagonist
Not often first line
Used in combo with other glaucoma meds
Mode of action: inhibits production of aqueous humour by acting as agonists of alpha receptors sympathomimetic activity - mimics natural effect of norepinephrine via stimulation of alpha receptors
Adrenergic agonists act on alpha 2 receptors - alpha 2 agonists
Alpha 2 agonists
Brimonidine tartrate
Apraclonidine - used to control IOP during and after Intraocular surgery
Side effects of alpha 2 agonists
- Allergic conjunctivitis
- Dry mouth
- Fatigue and drowsiness
- Drug interaction: monoamine oxidase inhibitors (used to treat depression)
Miotic
Mode of action: enhance aqueous humour outflow
Cholinergic activity: mimic parasympathetic branch of ANS
Promotes pupil constriction and ciliary muscle contraction
Widen drainage channels within trabecular mesh work
Example of a miotic
Pilocarpine - eyedrops
Another advantage – depth of focus = pinhole effect. No blur circle on retina. Good VA whether glasses or not
Carbonic anhydrase
Mode of action: inhibit production of aqueous humour
What are some examples of carbonic anhydrase inhibitors
Dorzolamide
Brinzolamide
Medications for primary angle closure glaucoma
Osmotic agents:
Increase blood osmolality levels
Blood - aqueous barrier prevents osmotic agent from entering eye
Creates an osmotic gradients - aqueous drawn away from eye into blood stream
IOP drops rapidly
E.g. glycerol
What else is used for managing PACG
Acetazolamide
- systemic carbonic anhydrase inhibitors
- inhibit production of aqueous humour
Osmotic agent
Pilocarpine - break pupil block
Topical prostaglandin analogues, beta blockers and carbonic anhydrase inhibitors
Peripheral iridotomy
What are the different categories of glaucoma medications
- Prostaglandin analogues
- Beta blockers
- Adrenergic agonists
- Miotic
- Carbonic anhydrase inhibitors
