Pharmacology of MIOTICS, MYDRIATICS.pptx

Miotics are drugs that cause constriction of pupil.
The commonly used miotics belong to two groups

a) parasympathomimetics (contraction of circular fibres of iris)
b) sympatholytics (relaxing dilator pupillae muscle)

Mydriatics are drugs that dilate the pupil while cycloplegics are agents that cause paralysis of ciliary muscle (paralysis of accommodation)
The commonly used mydriatics belong to two groups
a) sympathomimetics
b) parasympatholytics
MIOTICS
Agents which cause constriction of pupil
These are used in the management of glaucoma and the treatment of esotropias and accommodation insufficiency.

Pilocarpine
Direct acting parasympathomimetic drug
Duplicates the muscarinic effects of acetylcholine (M3 receptor), but has no nicotinic effects.
It is effective in the treatment of glaucoma by decreasing intraocular tension
improves the aqueous humor outflow
Decreases aqueous secretion.

Onset of miosis occurs within 10-30 mins and lasts for 4-8 hours following topical application.
Indications and Usage
The control of intra-ocular pressure in angle closure glaucoma.
To reverse mydriasis caused by a cycloplegic agent.
In the treatment of accommodative strabismus.







Controversial role in the treatment of hyphaema.
After cataract extraction in cases of intra capsular cataract extraction
Adverse effects
Visual blurring
poor dark adaptation caused by the failure of the pupil to dilate in reduced illumination
Brow pain
Nausea
Diarrhoea
Sweating
Bronchospasm

Dosage and Administration
Pilocarpine nitrate, a sterile ophthalmic solution is available as 1%, 2% or 4% drops
To aid in emergency miosis, 1 to 2 drops of one of the higher concentrations should be used.
Carbachol
Carbachol is a direct acting parasympathomimetic that is used when allergy or resistance to pilocarpine develops
It has both nicotinic and muscarinic actions and also partially inhibits cholinesterase
Available as 0.75 % - 3 % drops.
Used for lowering intra-ocular pressure and pupillary constriction in the treatment of glaucoma.
When instilled into the eye, it mimics the effects of Ach, causing miosis and spasm of accommodation in which the ciliary muscle of the eye remains in a constant state of contraction.
Onset of action = 10-20min
Intraocular pressure is reduced for 4-8hrs.
Adverse effects
Little or no side effects occur due to lack of systemic penetration

Dosage and Administration
It is administered three to four times per day.
Physostigmine Sulphate
An indirectly acting parasympathomimetic agent which is reversible anticholine-esterase.
Given as 0.25% eye drops with 2% pilocarpine nitrate.
The mechanism of action involves inhibition of choline-esterase with consequent accumulation of acetylcholine at the neuromuscular junctions.
Topical application produces miosis which lasts for 6-24hrs.

Dosage and Administration
0.1-1% eye drops
It is administered every 4 to 6 hours

Adverse Reaction
Twitching
Irritation
allergic reaction
Depigmentation of the eye lid skin

1. MYDRIATICS & MIOTICS Miotics are drugs that cause constriction of pupil. The commonly used miotics belong to two groups a) parasympathomimetics (contraction of circular fibres of iris) b) sympatholytics (relaxing dilator pupillae muscle) Mydriatics are drugs that dilate the pupil while cycloplegics are agents that cause paralysis of ciliary muscle (paralysis of accommodation) The commonly used mydriatics belong to two groups a) sympathomimetics b) parasympatholytics

2. MIOTICS Agents which cause constriction of pupil These are used in the management of glaucoma and the treatment of esotropias and accommodation insufficiency. Pilocarpine Direct acting parasympathomimetic drug Duplicates the muscarinic effects of acetylcholine (M3 receptor), but has no nicotinic effects. It is effective in the treatment of glaucoma by decreasing intraocular tension improves the aqueous humor outflow Decreases aqueous secretion. Onset of miosis occurs within 10-30 mins and lasts for 4-8 hours following topical application.

3. Indications and Usage The control of intra-ocular pressure in angle closure glaucoma. To reverse mydriasis caused by a cycloplegic agent. In the treatment of accommodative strabismus. Controversial role in the treatment of hyphaema . After cataract extraction in cases of intra capsular cataract extraction

4. Contraindications: Contraindicated in anterior uveitis.

5. Adverse effects Visual blurring poor dark adaptation caused by the failure of the pupil to dilate in reduced illumination Brow pain Nausea Diarrhoea Sweating Bronchospasm Dosage and Administration Pilocarpine nitrate, a sterile ophthalmic solution is available as 1%, 2% or 4% drops To aid in emergency miosis, 1 to 2 drops of one of the higher concentrations should be used.

6. Carbachol Carbachol is a direct acting parasympathomimetic that is used when allergy or resistance to pilocarpine develops It has both nicotinic and muscarinic actions and also partially inhibits cholinesterase Available as 0.75 % - 3 % drops. Used for lowering intra-ocular pressure and pupillary constriction in the treatment of glaucoma. When instilled into the eye, it mimics the effects of Ach, causing miosis and spasm of accommodation in which the ciliary muscle of the eye remains in a constant state of contraction. Onset of action = 10-20min Intraocular pressure is reduced for 4-8hrs.

7. Adverse effects Little or no side effects occur due to lack of systemic penetration Dosage and Administration It is administered three to four times per day.

8. Physostigmine Sulphate An indirectly acting parasympathomimetic agent which is reversible anticholine -esterase. Given as 0.25% eye drops with 2% pilocarpine nitrate. The mechanism of action involves inhibition of choline-esterase with consequent accumulation of acetylcholine at the neuromuscular junctions. Topical application produces miosis which lasts for 6-24hrs. Dosage and Administration 0.1-1% eye drops It is administered every 4 to 6 hours Adverse Reaction Twitching Irritation allergic reaction Depigmentation of the lid skin has been noted in some patients with the use as an ointment.

9. Mydriatics Mydriatics are drugs that cause dilatation of pupil. There are 2 categories of mydriatics a) α-adrenergic agonists (sympathomimetics)= stimulate α 1 receptors in radial muscle fibers of iris without causing cycloplegia ex: Adrenalin, phenylephrine, cocaine etc. b) muscarinic antagonists= by blocking muscarinic receptors , causes paralysis of iris and ciliary body leading to cycloplegia. Ex: homatropine, tropicamide, cyclopentolate Phenylephrine Hydrochloride Phenylephrine hydrochloride is a direct acting drug that stimulates the alpha-receptors of those structures innervated by the post ganglionic sympathetic nerve fibres . It is a mydriatic with no cycloplegic effect

10. It is used in diagnosis of ptosis of Horner's syndrome (1.0 per cent phenylephrine causes dilation of a horner's pupil but not of a normal pupil). Contraindications Angle closure glaucoma. Hypertensive patients: Phenylephrine is a powerful vasoconstrictor and is absorbed systemically when applied topically to the eye.

11. Available as 5- 10% eye drops. Maximum dilation with phenylephrine alone occurs within 15 -60 minutes The pupil size returns to normal within 4 -6 hours. Adverse Effects Ophthalmic : Mild stinging on initial instillation Systemic : systemic hypertension Tachycardia Headache or browache Episodes of myocardial infarction and arrhythmias in elderly patients are reported.

12. Atropine Sulphate It is an anti-cholinergic that acts as Mydriatics and Cycloplegics Cycloplegics are drugs that cause paralysis of ciliary muscles, i.e., cause relaxation of accommodation. Available as 0.5 %, 1 % and . 3.0 % eye drops and ointments Acts directly on the muscarinic receptors of structure innervated by the post-ganglionic parasympathetic fibres Causes mydriasis and cycloplegia by paralysing sphincter pupillae (circular iris muscle) and ciliary muscle respectively Indications and uses It is used for mydriasis and cycloplegia Amblyopia therapy Pre and post operatively in many intra-ocular surgeries

13. Adverse Reaction Local: Redness and crusty flaking of the eyelid margins, dryness and wrinkling of the skin around the eyelids Blurred vision and photophobia Systemic: Dryness of skin and mouth, Tachycardia Irritability Delirium flushing of face skin rash abdominal distension in infants

14. Dosage and Administration Because of a long duration of its effect and delay in the onset of action it is not routinely used Homatropine Hydrobromide It is 2 % sterile ophthalmic solution, first anti -cholinergic to be developed specifically as an alternative to atropine. It is a synthetic anti -cholinergic agent that directly blocks the muscarinic action of acetylcholine, causing mydriasis and cycloplegia. Adverse reactions are similar to atropine but much less in frequency

15. Cyclopentolate Hydrochloride Cyclopentolate 1 % is an anticholinergic produces maximum mydriasis in 20-30min. Also available as 0.5 % and 2 % solution. Also used for pre and post -operative states when mydriasis is required. Used when a short acting mydriatic cycloplegic is needed in the therapy of , iridocyclitis (inflamed iris and ciliary body ). Complete recovery usually occurs in 24 hours. Contraindications In Angle closure glaucoma

16. Tropicamide It is an anti-cholinergic mydriatic Has rapid onset of action and low incidence of side effects. It is available as 0.5 % or 1 % eye drops. Tropicamide acts by blocking muscarinic acetylcholine receptors. Dosage and administration One or two drops of 1 % solution in each eye 2 to 3 times at 5 minutes intervals or as directed by the physician. Adverse Reaction Local: Stinging sensation Systemic: Rarely in children, confusion or hyperactivity may occur