DRUGS ACTING ON THE
EYE
PREPARED BY MR. ABHIJIT DAS
MIOTICS
Miotics are medications that constrict the pupil and
increase the outflow of aqueous humor from the eye.
CLASSIFICATION
1.
Direct-acting miotics: These drugs
directly bind to and activate the muscarinic receptors in the eye, causing
pupillary constriction and increased outflow of aqueous humor. Examples include
pilocarpine and carbachol.
2.
Indirect-acting miotics: These drugs
work by inhibiting the enzyme acetylcholinesterase, which breaks down
acetylcholine. This leads to an accumulation of acetylcholine in the eye,
resulting in pupillary constriction and increased outflow of aqueous humor.
Examples include echothiophate and physostigmine.
PILOCARPINE
MOA
Pilocarpine is a direct-acting cholinergic agonist
that binds to muscarinic receptors in the eye. This stimulates the
parasympathetic nervous system, causing the circular muscles in the iris to contract and the pupil
to constrict. Additionally, pilocarpine increases the outflow of aqueous
humor from the eye, which helps to lower intraocular pressure.
ADVERSE EFFECTS
1.
Blurred vision
2.
Eye irritation
3.
Headache
4.
Eye pain
5.
Increased tearing
THERAPEUTICAL USES
1.
Treatment of glaucoma
2.
Relief of intraocular pressure
3.
Management of dry eyes in Sjogren's
syndrome.
PHYSOSTIGMINE
MOA
Physostigmine works as a miotic by inhibiting
acetylcholinesterase, an enzyme that breaks down acetylcholine. This leads to
an accumulation of acetylcholine, which stimulates the cholinergic receptors on
the circular muscles of the iris causing them to contract, resulting in pupil
constriction.
ADVERSE EFFECTS
1.
Nausea and vomiting
2.
Diarrhea
3.
Sweating and salivation
4.
Bradycardia (slow heart rate)
5.
Hypotension (low blood pressure)
THERAPEUTICAL USES
1.
Treatment of glaucoma
2.
Pupillary constriction during eye
surgery
3.
Diagnosis and treatment of atropine
overdose.
MYDRIATICS
Mydriatics are drugs that dilate the pupil of the
eye by blocking the action of acetylcholine at the pupillary sphincter muscle.
They are used to facilitate eye examinations and surgery.
CLASSIFICATION
1. Anticholinergic
mydriatics include atropine, homatropine, and tropicamide, which block the
action of acetylcholine at the pupillary sphincter muscle.
2. Adrenergic
mydriatics, such as phenylephrine and ephedrine, work by stimulating the
sympathetic nervous system to cause pupillary dilation.
ATROPINE
MOA
Atropine works as a mydriatic by blocking the action
of acetylcholine at the pupillary sphincter muscle, which leads to pupillary
dilation.
ADVERSE EFFECTS
1.
Blurred vision and photophobia
2.
Dry mouth and skin
3.
Tachycardia (rapid heart rate)
4.
Confusion and agitation (in high doses)
THERAPEUTICAL USES
1.
As a mydriatic to dilate the pupil for
examination of the eye
2.
To treat certain eye conditions such as
iritis
EPHEDRINE
MOA
Ephedrine works as a mydriatic by stimulating the
release of noradrenaline, which activates adrenergic receptors in the iris
dilator muscle. This leads to pupillary dilation by contraction of the radial
muscles of the iris.
ADVERSE EFFECTS
1.
Anxiety and restlessness
2.
Palpitations and tachycardia (rapid
heart rate)
3.
Hypertension (high blood pressure)
4.
Nausea and vomiting
5.
Insomnia and headaches
THERAPEUTICAL USES
1.
As a mydriatic agent to dilate the pupil
for ophthalmic examinations
2.
To relieve symptoms of eye allergies and
conjunctivitis
DRUGS USED IN GLAUCOMA
GLAUCOMA
Glaucoma is an eye disease that damages the optic
nerve and causes vision loss, often due to increased intraocular
pressure (IOP) that damages the optic nerve over time.
CLASSIFICATION OF DRUGS USED IN GLAUCOMA
1.
Adrenergic agonists - drugs that reduce intraocular
pressure (IOP) by decreasing aqueous humor production. Examples include
brimonidine and apraclonidine.
2.
Beta-2 blockers - drugs that reduce IOP
by decreasing aqueous humor production. Examples include timolol and betaxolol.
3.
Miotics - drugs that constrict the pupil
and increase outflow of aqueous humor, reducing IOP. Examples include
pilocarpine and carbachol.
4.
Prostaglandin analogs - drugs that
increase aqueous humor outflow by relaxing the ciliary muscle. Examples include
latanoprost, travoprost, and bimatoprost.
LATANOPROST
MOA
Latanoprost works by activating prostaglandin
F2-alpha receptors in the eye, which increases the outflow of aqueous humor by
relaxing the ciliary muscle, resulting in a reduction of intraocular pressure
in glaucoma.
ADVERSE EFFECTS
1.
Redness
or itching of the eyes
2.
Changes in the color or thickness of the
eyelashes
3.
Darkening of the iris (colored part of
the eye)
4.
Increased sensitivity to light
THERAPEUTICAL USES
1.
Treatment of open-angle glaucoma
2.
Management of ocular hypertension
3.
Prevention of further damage to the
optic nerve in patients with elevated intraocular pressure