Miotics

Question 1

What is pilocarpine used for?

Answer 1

ACG emergency management (IOP reduction)
Reversal of mydriatics
Long term glaucoma treatment (IOP reduction)

Question 2

What is pilocarpine’s mechanism of action?

Answer 2

Parasympathomimetic (direct adrenergic agonist)
Blocks adrenergic muscarinic receptors, mimicking ACh.
Encourages iris sphincter to contract (causing miosis) and the ciliary muscle to contract, opening the trabecular meshwork and Schlemm’s canal, allowing an increased aqueous outflow, therefore reducing IOP

Question 3

What are other miotic mechanisms of action?

Answer 3

AChE inhibitors (causes gathering of ACh at receptors causing prolonged miosis)
Anti-adrenergic (blocks adrenergic receptor, relaxing iris dilator)

Question 4

What are the contraindications for pilocarpine?

Answer 4

Known hypersensitivity
Uveitis
Iris-mounted IOL
Iridectomy
Retinal detachment history

Question 5

What are the ADRs of pilocarpine?

Answer 5

Accommodative spasm (due to ciliary muscle action - generally unbearable for under 40s)
Pupil miosis (due to iris sphincter action - issue if central cataract present)
Frontal headache
Poss pupil block and angle closure risk (if narrow angles or nuclear cataract)
RD risk (due to constant contraction of ciliary muscle pulling on vitreous and retina - risk higher if myopic, pseudophakic or aphakic)
Systemic (nausea, vomiting, weakness, salivation, bronchospasm, pulmonary oedema)