Medical Management of Glaucoma Flashcards
B adrenergic antagonist and prostaglandin analogue
- B adrenergic antagonist = was commonly used
- prostaglandin analogue = now is first line of treatment for glauc therapy as it has a sim pressure lowering effect to beta blockers but has a safety profile
target IOP
= upper limit of the IOP estimated to be compatible with a rate of progression suffciently slow to maintain vision related quality of life for the expected lifetime of the px
- no single target IOP that is appropriate for every px and needs to be determined individually
- all drugs licensed to treat glaucoma are licensed as IOP lowering agents
- IOP lowered by 20-35% (approx 5-7mmHg on avg)
LiGHT trial
- Lancet published a study earlier this year on the LiGHT trial, a multicentred double masked RCT comparing selective laser trabeculopasty (SLT) to eye drops for treat pxs with open angle glaucoma, which found SLT provided more robust IOP lowering while being a more cost efficient first line treatment
- SLT could be offered as a first line treatment for open angle glaucoma and ocular htn
classes of drugs (topical)
- prostoglandin agonists
- beta receptor antagonists
- alpha 2 receptor agonists
- carbonic anhydrase inhibitors
- cholinergic receptors
mechanism of action: topical drugs
- reduce aqueous production (CAI’s, a receptor agonists, and b receptor antagonists)
- increase outflow through the trab meshwork (cholinergics)
- increase uveoscleral flow (PGA, prostamide, brimonidine)
classses of drugs (systemic)
- tend to be used in px with acute angle closure
- carbonic anhydrase inhibitors eg acetzolamide (diamox)
- osmotic agents eg glycerol, mannitol
what to do before prescribing any new drop for glaucoma
- general medical history
- drug history
- history of topical allergy
- find out if the px can use eye drops (memory and dexterity, carers)
what to look for when choosing a drug
- efficacy
- safety
- compliance
- cost
order of efficacy of topical drugs
1) prostaglandin agonists 25-35%
2) beta antagonists 20-30%
3) alpha 2 agonists 18-25%
4) cholinergic agonists 20-25%
5) carbonic anhydrase inhibitors 20% - rarely used in first line, tend to be used in conjunction
which PGA to use
prostaglandin analogues:
1) Latanoprost (non proprietary and xalatan) - dose 50micrograms/ml
2) Travoprost (travatan) - dose 40 micrograms/ml
3) Tafluprost (saflutan) - dose 15 micrograms/ml - unit dose
prostamide
- bimatoprost (lumigan) - 100micrograms/ml - acts on uvoscleral pathway so similar mode of action to PGAs
PGA: side effects
- darkening, thickening and lengthening of the eyelashes
- increased iris pigmentation - doesnt tend to affect blue/green eyes
beta antagonists
1) Timolol maleate (non proprietary and timoptol 0,5% and tiopex 1mg/g)
2) Betaxolol (betoptic) 0.25% - available as unit dose
3) Levobunolol HCl (betagan) 0.5% - available as unit dose
timolol = non selective - binds to b1 and b2 receptors betaxolol = selective - B1 receptor blocker, avoids bronchoconstriction
fixed combinations of beta antagonists
- latanoprost with timolol (non proprietary)
- bimatoprost with timolol (ganfort)
- brimonidine with timolol (combigan)
- dorzolamide with timolol (corsopt)
beta antagonists side effects
- glacoma and airway disease frequently co exist
- glauc affects 5% of people over 65
- airways obstruction affects 40% of people over 75
- main side of beta blockers is they can cause bronchoconstriction esp in pxs with obstructive airways disease or asthma - lungs have b2 receptors and stimulating/ blocking these receptors causes bronchoconstriction
unrecognised respiratory impairment by topical b antagonists
- timolol may impair respiratory function and exercise tolerance of elderly pxs even if they have no history of reversible airways disease
