Pharmacotherapy of glaucoma
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Transcript of Pharmacotherapy of glaucoma
Pharmacotherapy of . Glaucoma
Dr Manjuprasad
Moderator: Dr Vijayalaxmi M.K
Overview
• Introduction
• Anatomy
• Aqueous humour dynamics
• pathophysiology
• Drugs used in the treatment
• Recent advances
• Conclusion
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Introduction• Glaucoma – ancient greek
meaning clouded or blue- green hue
• In Hippocratic aphorisms
Glaucoma – blindness coming from advancing years
• Second leading cause of blindness
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• Glaucoma is not a single disease process but a group of disorders characterized by a progressive optic neuropathy resulting in a characteristic appearance of optic disc & specific pattern of irreversible visual field defects that are associated frequently but not invariably with ↑IOP
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Anatomy of the eye
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Aqueous humor• Derived from the plasma
• 2.3µl/min
Production:
• Ultrafiltration
• Secretion
• Diffusion
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Aqueous humor dynamics
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Classification
• Congenital glaucoma
- Primary congenital glaucoma
- Developmental glaucoma
• Primary adult glaucoma
- Primary open angle glaucoma
- Primary angle closure glaucoma
- Primary mixed mechanism glaucoma
• Secondary glaucoma 8
Pathogenesis • All types of glaucoma – progressive optic neuropathy due to the
death of retinal ganglion cells(RGCs)
• RGCs death is initiated – block in transport of neurotrophins
from brain to RGCs
damaging cascade activation
Apoptosis of RGCs
• RGCs death – loss of retinal fibers – optic neuropathy & visual
field defects 9
• Mechanical theory :
↑IOP – mechanical stretch of lamina cribrosa – axonal deformation & altered capillary blood flow -- ↓neurotrophinsto reach RGC`s
• Pressure independent factors
- Failure of autoregulation
- Vasospasm
- Systemic hypotension
- Blood / fluid loss
• Excitotoxicity theory:
glutamate , oxygen free radicals, nitric oxide10
Congenital glaucoma
• Seen in 1 in 10,000 births
• Pathology- mal development of trabeculum
• True congenital glaucoma• Infantile glaucoma• Juvenile glaucoma
• Diagnosis – corneal diameter measurement- ophthalmoscopic evaluation of disc- gonioscopic examination 11
Primary open angle glaucoma
• No obvious cause
• Polygenic inheritence
• ↑incidence in smokers
• Blacks > whites
• Pathology:
- Age related thickening & sclerosis of trabeculae
- Absence of giant vacuoles in cell lining canal of schlemm
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Primary angle closure glaucoma• Increase in IOP – due to closure of angle of anterior chamber.
Acute & chronic
• Chronic PACG:- progress slowly with / without symptoms
• Acute PACG:-
-Is an emergency
-Severe eye pain
-Nausea, vomiting, prostration
-Redness, photophobia, lacrimation
-Rapid, progressive impairment of vision13
Risk factors:
• Hypermetropic eye
• Small eye
• 5th decade
• Female > male
• > in rainy season and dim light
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Secondary glaucomas• Lens induced glaucoma
• Pigmentary glaucoma
• Neovascular glaucoma
• Glaucoma associated with intravascular tumor
• Traumatic glaucoma
• Steroid induced glaucoma
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Drugs used in the treatment
DRUGS THAT REDUCE AQUEOUS HUMOUR PRODUCTION
I. Beta-Blockers : levobunolol, timolol, carteolol, betaxolol
II. Alpha-2 Adrenergic Agonists : apraclonidine, brimonidine
III. Carbonic Anhydrase Inhibitors :acetazolamide, dorzolamide 17
DRUGS THAT INCREASE AQUEOUS OUTFLOW
I. Nonspecific Adrenergic Agonists :epinephrine, dipivefrin
II. Parasympathomimetics : pilocarpine, carbachol, echothiophate
III. Prostaglandin Analogues : latanoprost
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Cholinergic agonists• Most commonly used – Pilocarpine
• Derived from shrub – pilocarpus jaborandi
MOA:-
• Acts on M3 receptors
– contraction
of sphincter pupillae
• Causes contraction of
longitudinal ciliary muscle →
trabecular outflow19
• Onset of action – rapid
peak effect – 30min
lasts for 4 – 6hrs
• S/E:-
• LOCAL:- Superficial punctate keratitis , brow ache, induced myopia, increased risk of retinal
detachment & iritis
• SYSTEMIC – rare
• Available as 0.5 to 10 % eye drops
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• Pilocarpine gel (pilocarpine HCl 4%) HS
• Membrane controlled delivery system:-
-Insert placed in cul-de-sac that gradually release drug at rate of 20mcg/hr
-Effective for 7 days
• Pilocarpine soaked contact lens
• Liposomal pilocarpine
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ADRENERGIC AGONISTS
Includes:
• Non selective – epinephrine & dipivefrin
• Selective alpha2 agonists- Apraclonidine, Brimonidine
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• EPINEPHRINE:-
• Directly acting sympathomimetic
• MOA:
• Reduced aqueous production due to alpha action
• trabecular outflow via Beta receptor stimulation
• Due to its CVS s/e , allergic reaction – no longer used
• DIPIVEFRIN:-
• Is a prodrug
• Formed by di-esterification of epinephrine –lipophilicity– increased penetration to anterior chamber .
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• Onset of action-30min, peak effect – 1hr
• Used as an adjuvant therapy
• Available as 0.1% solution , dosage BD
A/E :
• Less compared to epinephrine
• Follicular conjunctivitis, blurring of vision, stinging
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ALPHA2 AGONISTSMOA:-
• Decrease aqueous humour production by alpha2 action on ciliary epithelium.
APRACLONIDINE:
• Also known as para amino clonidine
• Available as 0.5 – 1 % , dosage BD
• Short term use – Post op rise in IOP & adjuvant in POAG
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BRIMONIDINE:-
• 30 times more selective α2 agonist than apraclonidine
• Additional neuroprotective effect
• Available as 0.2 - 0.5% , applied BD
• Uses:- in patients with contraindications to beta blockers,
-short term use in post op raise in IOP
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BETA BLOCKERS
• Introduced in 1979
• Considered to be 1st line therapy for all types of glaucoma
• Good efficacy
• Minimal S/E
MOA:
• Decreases aqueous humour production by blocking beta2 receptors on ciliary epithelium.
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TIMOLOL:
• Introduced 1978 as 1st approved beta blocker for glaucoma
• Most widely used ocular hypotensive agent
• Due to its non selective beta action – cautious in COPD, asthma & heart failure
• Available as 0.5 % solution & gel
• S/E:-
• Systemic
• Local:- superficial punctate keratitis, corneal anesthesia
CARTEOLOL:
• Available as 1% solution28
• LEVOBUNOLOL
• Available as 0.5 – 1% solution, applied BD /OD
• Metabolized to di- hydrolevobunolol
• BETAXOLOL
• Introduced in 1980s as 1st topical β1 blocker used in glaucoma
• Clinical trials – lesser efficacy in reducing IOP compared to timolol
• Additional neuroprotective effect.
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CARBONIC ANHYDRASE INHIBITORS
2 types:-
• Systemic CA inhibitors:-
• Acetazolamide, Methazolamide
• Topical CA inhibitors:-
• Dorzolamide, Brinzolamide
MOA:-
• Blocks CA enzyme reversibly in ciliary body – reduces aqueous humour production
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SYSTEMIC CARBONIC ANHYDRASE INHIBITORS
DOSAGE:-
• Acetazolamide 125mg, 250mg p.o TID or QID
• Methazolamide 25mg, 50mg p.o BD or TID
SIDE EFFECTS:-
• High risk of systemic S/Es.
• Paraesthesias, Kidney stones, aplastic anaemia, depression
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TOPICAL CARBONIC ANHYDRASE INHIBITOR
• DORZOLAMIDE:-
• 1st topical CA inhibitor launched in market
• Advantage – not absorbed systemically
• Available as 2 % solution- applied TID
• S/E:- systemic is minimal
- local S/E includes corneal edema, allergic reaction, burning & stinging sensation
• BRINZOLAMIDE
• Available as 1% solution
• Better tolerated than dorzolamide – its pH is 7.4 32
PROSTAGLANDIN ANALOGUES
• Includes latanoprost, unoprostone, bimatoprost, travoprost.
• MOA:-
• Decreases IOP by increasing uveoscleral
outflow
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LATANOPROST:-
• Introduced in 1996
• An ester prodrug analogue of PGF2α
• Available as 0.0005% solution, OD (evening)
• Requires refrigeration & protection from sunlight
• S/E – conjunctival hyperemia ( initially), Iris
pigmentation, cystoid macular odema
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UNOPROSTONE:-
• Available as 0.15% solution, BD
• Additional neuroprotective effect – increasing microcirculation in optic nerve head.
BIMATOPROST:
• A synthetic prostamide analogue
• Available as 0.03% solution , OD
• Does not require refrigeration
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TRAVAPROST
• Synthetic PGF2α analogue
• Available as 0.004% solution, OD at evening
• Does not require refrigeration/ protection from sunlight
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Surgical procedures
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• Trabeculoplasty
• Iridotomy
• Iridectomy
• Filtering procedures
• Canaloplasty
• Goniotomy
• Goniocurettage
• Cyclodialysis
• Ciliarotomy
Other treatment modalitiesALPHA LIPOIC ACID:-
• Powerful antioxidant
• Useful in glaucoma by decrease in nerve cell damage due to oxidative stress
VITAMIN C :-
• Said to increase aqueous outflow by reducing viscosity of hyaluronic acid in trabecular meshwork
SALVIA MILTIORRHIZA:-
• Chinese herb, given i.v said to improve
microcirculation of RGCs 38
CANNABINOIDS
• Believed to improve uveoscleral outflow
• Not yet available for this purpose
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Herbal products
• Boerhavia Diffusa
• Emblica Officinalis
• Terminalia Chebulia
• Commiphora Mukul
• Curcuma Longa
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FUTURE GLAUCOMA THERAPY
• NMDA receptor antagonist:-
• Provides neuroprotection by blocking glutamate mediated death of RGCs
• Includes memantine & eliprodil
• Riluzole:-
• Is a presynaptic glutamate release inhibitor
• Neuroprotective nature
• Neuroprotective vaccines:- R16
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Erythropoetin:-
• Neuroprotective by inhibiting RGCs apoptosis
• In animal studies – intravitreal injection enhances RGC survival
Caspase inhibitors:-
• Inhibits apoptosis of RGCs
• Promising approach in terms of Rx of glaucoma
iNOS inhibitors:-
• Increased level of NO – neuronal damage via apoptosis
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DRUG ELUTING MICRO STENTS
• Microstents were coated with a polymer-drug compound and is implanted in the angle of iris and cornea
• Diffusion controlled
release of paclitaxel or
mitomycin is used to
avoid blocking of stent
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Acute angle closure glaucoma• IOP – 40-70 mmHg
• Systemic hyperosmotic agent- IV mannitol 1mg/kg
• Actazolamide 500mg IV followed by 250mg TID
• Analgesics and Antiemetics
• Corticosteroids e/d like dexamethasone 3-4/day to reduce inflammation
• Sx- periferal iridotomy
filteration surgery
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BIBLIOGRAPHY• Pharmacological aspects of therapeutics – Goodman and Gilman – 12th edition
• Principles of pharmacology Sharma and sharma 2nd edition
• Textbook of medical pharmacology – Dr.PadmajaUdaykumar – third edition
• Essentials of medical pharmacology – K.D.Tripathi
• A. K. Khurana - comprehensive ophthalmology
• Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol. 2006;90:262–7
• Killer HE, Miller NR, Flammer J, Meyer P, Weinreb RN, Remonda L, Jaggi GP. Cerebrospinal fluid exchange in the optic nerve in normal-tension glaucoma. Br J Ophthalmol. 2012;96:544–8.
• Collaborative Normal-Tension Glaucoma Study Group. The effectiveness of intraocular pressure reduction in the treatment of normal-tension glaucoma. Am J Ophthalmol. 1998;126:498–505
• . Bergeå B, Bodin L, Svedbergh B. Impact of intraocular pressure regulation on visual fields in open-angle glaucoma. Ophthalmology. 1999;106:997–1004
• Rao HL, Addepalli UK, Jonnadula GB, Kumbar T, Senthil S, Garudadri CS. Relationship between intraocular pressure and rate of visual field progression in treated glaucoma. J Glaucoma. 2012 In press.
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