ophthalmic drugs: anti-glaucoma Flashcards
list the 5 categories of drugs used to treat glaucoma
- Prostaglandin agonists
- Beta receptor antagonists
- Alpha 2 receptor agonists
- Carbonic anhydrase inhibitors
- Cholinergic agonists
all target different processes
which 2 ways can you bring IOP down
- by inhibiting aqueous production
or - by enhancing aqueous drainage
what are the 2 drainage pathways
- conventional pathway via the trabecular meshwork and canal of schlemm
or - uveoscleral pathway - 30%
where is the production of aqueous from
the ciliary body
what do patients with early to moderate glaucoma damage still retain
good central visual function
what is the aim for therapy used on glaucoma patients
to maintain ‘target IOP’ ie IOP that is expected to prevent further glaucomatous damage
what are most patient with OAG initially treated with and what is the other option
topical medication (start with single eyedrop, then adding other drops or using multiple therapies) other option is Laser trabeculoplasty
what is the name of a incisional surgical treatment for glaucoma and when is it considered
trabeculectomy may be considered in advanced glaucoma or high IOP
how much is IOP lowered by with glaucoma drugs and how much of aqueous does this correspond to
IOP lowered by 20-35%
corresponds to approx. 5 - 7mmHg
what is the normal episcleral venous pressure
8-10mmHg
what is the normal aqueous formation rate
2-3uL/min
what is the normal outflow facility of aqueous
0.2-0.3uL/min/mmHg
what is the mechanism of action with the topical anti-glaucoma drugs: CAI’s, α receptor agonists, and βreceptor antagonist
Reduce aqueous production
what is the mechanism of action with the topical anti-glaucoma drugs: cholinergics, bimatoprost
Increase outflow through the trabecular meshwork (the conventional method)
what is the mechanism of action with the topical anti-glaucoma drugs: PG agonists, brimonidine
Increase uveoscleral flow
what is the mechanism of action with the systemic anti-glaucoma drug: Carbonic anhydrase inhibitors and β receptor antagonists
Reduce aqueous production
tablets: Diamox or Dorzolamide
what is the mechanism of action with the systemic anti-glaucoma drug: mannitol, glycerol
Osmotic agents i.e. they pull water out of the vitreous
when are the systemic anti-glaucoma drugs used
- as a last option for people who are on maximum eye drops and their pressure is still too high
- used to treat acute angle closure attack when IOP really high and want to bring it down rapidly in A&E
list the 5 categories of anti-glaucoma drugs from highest to lowest efficacy
- Prostaglandin agonists
- Beta antagonists
- Alpha 2 agonists
- Cholinergic agonists
- Carbonic anhydrase inhibitors
which drug is the first choice for IOP reduction in OAG and newly diagnosed patients with glaucoma
Prostaglandin agonists
by which mechanism do Prostaglandin agonists work to reduce IOP
Increase uveoscleral outflow, reducing IOP by 25-33%
after how long from administration do Prostaglandin agonists reduce IOP and when is its peak effect
within 2-4 hours of administration
with peak effect 8-12 hours
how often should Prostaglandin agonists be administered
One drop preferably in the evening
which is an advantage as only one drop per day
what other drug is Prostaglandin agonists available with as a fixed combination
Timolol (beta antagonist)
list the 3 main Prostaglandin agonist drugs
- Latanoprost (Xalatan)
- Travoprost (Travatan)
- Tafluprost (Saflutan)
what is the trade name for the Prostaglandin agonist - Latanoprost
Xalatan
list 7 side effects of prostaglandin agonists
- Hyperaemia
- Eyelash growth (hypertrichosis)
- Iris darkening
- Darkening of periocular skin
- Reactivation of HSK
- Cystoid macular oedema in aphakes/pseudophakes
- Avoid in pregnancy as prostaglandins can induce labour
how do beta receptor agonists work in order to reduce IOP
Block β receptors (sympathetic) in ciliary epithelium, reducing aqueous humour formation
what are the 2 types of beta blockers available to treat glaucoma
- Selective beta blockers (ß1)
and - non-selective (ß1 and ß2) available
what can happen with beta receptor agonists drugs over time
tachyphylaxis (reduced effectiveness over time)
list the 4 non-selective beta receptor agonists drugs available
- Timolol (Timoptol, Nyogel)
- Levobunolol (Betagan)
- Metipranolol
- Carteolol (Teoptic)
name the selective beta receptor agonists drug available
Betaxolol (Betoptic)
what is meant by selective beta receptor agonists
drugs that only work on receptors that are in the eye and not on beta receptors in the lungs
however these type of drugs don’t work very effectively
what can non-selective beta receptor agonists be contraindicated in
those with airways disease
what does blocking β2 receptors cause
impair respiratory function by causing constriction of the bronchioles resulting in:
- shortness of breath
- wheezing
- bronchospasm
what 2 things may blocking β1 receptors cause
- bradycardia
- hypotension
= increased falls in elderly
what mechanisms does Alpha-2 receptor agonists use to reduce IOP
- Decrease aqueous production
and - Increase aqueous outflow
how does Alpha-2 receptor agonists decrease aqueous production
- because they’re sympathomimetic drugs, therefore they mimic the action of the sympathetic nervous system
- it inhibits aqueous production via alpha receptors by stimulating them
what disadvantage does Alpha-2 receptor agonists have
it displays tachyphylaxis
the drug works initially, but its effectiveness reduces overtime
name 2 Alpha-2 receptor agonists
- Apraclonidine hydrochloride (Iopidine)
- Brimonidine tartrate (Alphagan)
list the 7 side effects of Alpha-2 receptor agonist drugs
- Follicular conjunctivitis
- Allergy
- Dry mouth
- Headache
- Fatigue
- Dizziness
- Drowsiness
how does Carbonic anhydrase inhibitors reduce IOP
Decrease aqueous production by inhibiting enzyme involved in aqueous secretion
which types of formulations is Carbonic anhydrase inhibitors available in
topical and systemic
which formulation of Carbonic anhydrase inhibitors is used in treatment of acute angle closures
oral formulation
what is the topical form of Carbonic anhydrase inhibitors called
Dorzolamide
what is the systemic form of Carbonic anhydrase inhibitors called
Diamox/Acetazolamide tablets
which enzyme is involved in aqueous production and how does it work
carbonic anhydrase
it produces bicarbonate ions ( which may exert its effect on aqueous production by influencing Cl- movement as well as by transmembrane transport) which are transported across the ciliary epithelium, setting up a osmotic gradient one which aqueous production depends on
what happens when Carbonic anhydrase inhibitors block the carbonic anhydrase enzyme (that produces aqueous)
it inhibits the bicarbonate production, therefore lowers aqueous production
name the three Carbonic anhydrase inhibitor drugs available
- Brinzolamide (Azopt)
- Dorzolomide (Trusopt)
- Oral acetazolamide (Diamox)
what are the 2 topical versions of Carbonic anhydrase inhibitor drugs
- Brinzolamide (Azopt)
- Dorzolomide (Trusopt)
list the 5 side effects of topical Carbonic anhydrase inhibitor drugs
- Metallic taste (at back of throat, from the eye drops)
- Rashes
- Polyuria
- Irritation
- Blurred vision
list the 8 side effects of oral Carbonic anhydrase inhibitor drugs e.g. Diamox and Acetozolamide
- Allergy
- Hypokalemia
- Polyuria
- Acidosis
- Depression
- Paresthesia
- Kidney stones
- Blood dyscrasia
what type of drug are Cholinergic agonists
Parasympathomimetics (causes pupil constriction)
what is the pharmacological action/how do Cholinergic agonists reduce IOP
by increasing aqueous outflow by opening the trabecular meshwork
what is the mechanism of Cholinergic agonist drugs
they act as miotics and constrict the pupil, in doing so they potentially stretch the trabecular meshwork allowing for increased aqueous outflow
name 2 Cholinergic agonist drugs
- Pilocarpine – 0.1- 6%
- Pilogel
list 5 side effects of Cholinergic agonist drugs
- Miosis
- Myopia
- Symblepharon
- Post synechiae
- Retinal detachment (theoretical risk - very rare)
list the 5 categories of anti glaucoma drugs from the most to least safest i.e. least side effects to most side effects
- Prostaglandin agonists
- Cholinergic agonists
- Carbonic anhydrase inhibitors
- Alpha adrenergics
- Beta antagonists
what are none of the anti glaucoma eye drops licensed for
use in children and pregnant women
what are all combination drugs combined with and why are drugs combined
- all combined with a topical beta blocker Timolol 0.5%
- combined and patients are more compliant than using 2 separate drugs
list the 6 available combined anti glaucoma drugs
- Xalacom
- Duotrav
- Ganfort
- Combigan
- Cosopt
- Azarga
which 2 drugs make up Xalacom
Timolol + Latanoprost
which 2 drugs make up Duotrav
Timolol + Travoprost
which 2 drugs make up Ganfort
Timolol + Bimaptoprost
which 2 drugs make up Combigan
Timolol + Brimonidine
which 2 drugs make up Cosopt
Timolol + Dorzolamide
which 2 drugs make up Azarga
Timolol + Brinzolamide
what guidelines need to be followed for new prescriptions of anti glaucoma drugs
- Start only one drug regardless of presenting IOP in COAG (to look at the effectiveness of that drug)
- Show the patients how to put the drops in
- Check IOP again within 3 months (to see if the drug is working)
what is used to check peak flow when a px is on beta antagonists and what does it measure
- peak flow meter
- a device that measures lung functions, it measures the lung volume to diagnose lung problems and is measured before prescribing beta blockers
what needs to be done is more than 2 drops of anti glaucoma drugs are required
surgery or laser