Ocular hypotensive drugs Flashcards
HOw does mannitol work?
Hyperosmolar agent
Does not cross blood aqueous barrier
Removes water from eye by osmosis
Can decrease IOP through to be due to hypothalmic efferents travelling with optic nerve
should mannitol be cautioned with renal failure?
Excreted 90% unchanged by kidney
Can lead to side effects such as fluid retention and pulmonary oedema
What are risks of glycerol administration”?
Hyperglycaemia
Hyperosmotic coma
DKA in diabetics
What is the function of carbonic anhydrase? Where is it found? In eye?
CAtalyses H+ + HCO3- -> H2CO3
Buffers acid and base regulation
Found in proximal tubule cells which d=produce bicarb to buffer pH in urine
In non-pigmentary ciliary epithelium, stimulates aqueous production by increasing bicarb availbilaity for co-transport with sodium or increasing H+ concentration at inner membrane for sodium transport
What is acetazolamide?
Carbonic anhydrase inhibitor
Marked rapid decrease in IOP
What are side effects of diamox? Contraindication
Paraesthesia (most common)
Depression
GI upset
Hypokalaemia
CI in renal failure
What is dorzolamide?
Topical CAI
Has an ampholytic character - water soluble at pH 5 and 9 but lipid soluble at pH 7
Allows them to pass through lipophilic cornea to reach ciliary epithelium and inhibit carbonic anhydrase isoenzyme II
What are side effects of dorzolamide?
Electrolyte imbalance
Renal stones
General malaise
Bitter tast in mouth
Burning on instiallation
What is latanoprost?
PGF2alpha analogue
Modified by addition of isopropyl ester
Lipophilic prodrug that undergoes enzyme hydrolysis in cornea to activate
How does latanoprost work? Travoprost? Bimatoprost?
Increasing uveoscleral outflow
No effect on aqueous production
Minimally increases trabecular outflow
TRavoprost adn latanoprost increase uveoscleral outflow
Bimatoprost increases both uveoscleral and trabecular outflow
What is the half life in the eye of latanoprost
3 hours
What are side effects of latanoprost
Brown pigmentation of the iris
secondary to increased melanogneesis by iris stromal melanocytes
Lash trichaisis
Peri-orbital fat atrophy
Rare uvitis and CMO
What happens to latanoprost in the cornea?
Hydrolysed by corneal esterase to activate
Which general anaesthetic lower IOP RAises?
Halothane lowers IOP
Ketamine and Succinylcholine raise IOP
Which topical ocular hypotensive should be avoided in children?
Apraclonidine and brimonidine
Alpha 2 agonists as they can cross the blood brain barrier
