Ocular Pharmacology

Question 1

Write down the action of atropine on eye. (DU-23N)

Answer 1

Effects on ocular smooth muscles:

➤ Effects on constrictor (sphincter) pupillae muscle: Relaxation of constrictor (sphincter) pupillae muscle → dilation of pupil (Mydriasis).

➤ Effects on cilliary muscle: Relaxation of cilliary muscle → cycloplegia → obstruction of the “canal of Schlemm” & loss of light & accommodation reflex & photophobia → ↓ drainage of aqueous humor → ↑ intra-ocular pressure.

➤ Effects on lacrimal glands: ↓ Lacrimal gland secretion → lacrimation → dry eyes.

Question 2

Enlist the atropine like substitutes according to their uses. (DU-23N)

Answer 2

Atropine substitutes/atropine-like drugs:
• Mydriatics - homatropine, cyclopentolate, tropicamide
• Bronchial asthma - ipratropium, tiotropium.

• Antiparkinsonian drugs - benztropine, benzhexol, orphenadrine

• Antispasmodics - hyoscine N-butyl bromide, dicyclomine

• Peptic ulcer disease - pirenzepine, telenzepine M₁ blockers.

• Urinary incontinence - oxybutynin, tolterodine, propiverine

• Motion sickness - scopolamine
• For reversal of action of neostigmine - glycopyrronium

Question 3

Categorize the drugs used in glaucoma. Explain how physostigmine lowers intraocular
pressure. (DU-23N)

Answer 3

1.Pilocarpine - Muscarinic agonist
2.Ecothiophate:Anticholinesterase
3.Timolol - β blocker
4.Acetazolamoide, Dorzolamide - Carbonic anhydrase inhibitors
5.Clonidine, Apraclonidine – α₂ agonist
6.Latanoprost - Prostaglandin (PGF₂α) analogue

Physostigmine is the antidote for atropine poisoning and it reverses both central and peripheral effects of atropine.

Question 4

Mechanism of action. And adverse effects of 2 antiglaucoma drugs

Answer 4

1. Pilocarpine ( antimuscarinic)
   Decreases intraocular pressure - by contraction of sphincter pupillae muscle and ciliary muscle, iris is pulled away from anterior chamber and the trabecular meshwork at the base of the ciliary muscle is opened.

Both effects facilitates aqueous humor out flow into canal of Schlemm so ↓ intraocular pressure.

Adv effects
1.directly acting muscarinic stimulants
Nausea, vomitting, diarrheoa, salivation ,sweating ,miosis
2. Directly acting nicotinic stimulants
Convulsion ,coma ,paralysis, hypertension, cardiac arrhythmia

2. B blocker: timolol
   It reduces the formation of aq humor from ciliary body and decreases intra ocular pressure and improves the condition of glaucoma

Adv effects
Broncho constriction
Bradycardia
Hypotension
Heart failure
Heart block
Cold extremities
Nightmares depression
Suicidal thoughts

Question 5

Opc poisoning antidote

Answer 5

Atropine 0.6-1.8 mg iv every 10-25 mins till atropinization
Pralidoxime 1-2 mg over 15-30 mins repeated 4-6 times daily.
Diazepam if convulsions
Mgs04
Sodium bi carbonate if met acidosis

Question 6

why atropine is contraindicated in patient suffering from glaucoma. (DU-16Ju)

Answer 6

It causes relaxation of ciliary muscle causing cycloplegia.
This causes obstruction of canal of schlemn and depressed drainage of aq humor and inc intra ocular pressure

Question 7

Mention the role of pyridostigmine in myasthenia gravis. (DU-23N)

Answer 7

It has a prominent nicotinic effect than muscarinic effect.
It inhibits cholinesterase enzyme → no hydrolysis of ACh → ↑ concentration of ACh in the NMJ
→ opposite effect of Myasthenia gravis.

Question 8

Atropine antidote

Answer 8

Atropine poisoning (Physostigmine).

Question 9

Atropine poisoning management

Answer 9

General
Complete history
Initial abc management
Examination of vital signs
Catheterization
Gastric suction by 2% kmno4

Specific
Physostigmine 0.5-1 mg iv
Diazepam if convulsions
Antipyretic paracetamol