Physostigmine: Indication, Dosage, Side Effect, Precaution

This information is not country-specific. Please refer to the local prescribing information.

Generic Medicine Info

Indications and Dosage

Ophthalmic
Glaucoma

Adult: As sulfate, 0.25% ointment. As salicylate, 0.25% or 0.5% eye drops.

Oral
Alzheimer's dementia

Adult: Initial dose: 0.5 mg every 2 hr, 6 or 7 times daily until beneficial or adverse effects occur. Max dose: 16 mg/day.

Parenteral
Stimulate peristalsis in postoperative intestinal atony

Adult: Usual dose: 0.5-2 mg IV or IM inj.

Parenteral
Reversal of anticholinergic effect

Adult: Initial dose: 0.5-2 mg. May be given via slow IV inj or IM, repeated every 20 min until response or adverse effects occur. If initial doses are effective, additional doses of 1-4 mg may be given as necessary at usual intervals of 30-60 minutes as life-threatening signs recur.
Child: For life-threatening situations only: 0.02 mg/kg as initial dose. May be given via slow IV inj or IM, repeated at 5-10 min intervals until response or adverse effects occur or a total dose of 2 mg has been admin.

Contraindications

Acute iritis; acute uveitis; anterior uveitis; some forms of secondary glaucoma.

Special Precautions

Acute inflammatory disease of the anterior segment of the eye. Discontinue before eye surgery (risk of hyphema). History of retinal detachment, children with myopia. Night driving or hazardous task undertaken in poor illumination. Patients wearing soft contact lenses. Prolonged use may lead to depigmentation of the lid margins in dark-skinned patients.

Adverse Reactions

Systemic: CNS effects, may produce follicles in the conjunctiva, increased salivation, nausea, vomiting, abdominal cramps, diarrhoea, allergic reactions. Ophthalmic: Ciliary spasm, ocular pain and irritation, blurred vision, lachrymation, myopia, browache, conjunctival vascular congestion, superficial keratitis, vitreous haemorrhage, increased pupillary block, lens opacities (prolonged use).
Potentially Fatal: Respiratory failure.

Overdosage

May lead to "cholinergic crisis" which include excessive sweating, lachrymation, increased peristalsis, bradycardia and bronchospasm.

Drug Interactions

Aminoglycosides, clindamycin, colistin, cyclopropane, halogenated inhalational anaesthetics and atropine may antagonise the effects of physotigmine. Quinine, chloroquine, hydroxychloroquine, quinidine, procainamide, propafenone, lithium and β-blockers may reduce treatment efficacy. Prolonged bradycardia may occur when taken with β-blockers. May prolong the action of suxamethonium when used together.

Action

Description: Physostigmine is a reversible tertiary amine cholinesterase inhibitor, prolongs and intensifies physiological actions of acetylcholine.
Pharmacokinetics:
Absorption: Readily absorbed from the GI tract.
Distribution: Crosses the blood brain barrier.
Metabolism: Mainly by hydrolysis of the ester linkages by cholinesterases.
Excretion: Little excreted in urine.

Storage

Parenteral:
Store at 15-30°C.

MIMS Class

Antidotes & Detoxifying Agents / Antiglaucoma Preparations

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