Physostigmine

ANTILIRIUM

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Physostigmine ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Physostigmine ballicule

What it isReversible acetylcholinesterase inhibitor crossing the blood-brain barrier; severe central antimuscarinic delirium.

Why this oneIt reverses delirium and peripheral anticholinergic findings and can avert intubation when the toxidrome is clear.

What limits itGive slowly with ECG monitoring and atropine ready; avoid sodium-channel-blocker poisoning because arrhythmia and seizures may result.

Physostigmine molecular structure (skeletal formula) — Molecular structure: Physostigmine

FDA-approved for

anticholinergic toxicity (~1970)

FDA label

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FDA dosing	Population	Start	Max
Postoperative awakening disorders	Adult	0.04 mg/kg IV slow (~1 mg/min)	2 mg per single dose
Anticholinergic intoxication	Adult	0.04 mg/kg (2 mg) IV slow, then 1-4 mg every 20 min
Anticholinergic intoxication	Infants/children	0.5 mg IV, repeat every 5 min up to total 2 mg	2 mg total

Renal Undefined

Hepatic Undefined

Repeat the effective dose if intoxication symptoms recur; continuous infusion may be used.

Instructions

Inject slowly IV (~1 mg/min) or as brief infusion in 50 mL saline over 10-15 min
As antidote for TCA cardiotoxicity, use only with continuous ECG monitoring (risk of cardiac arrest)

Available strengths

inj 0.4, 1 mg/mL

Contraindications

Bronchial asthma
Gangrene (ulcers with tissue destruction)
Coronary heart disease
Mechanical bowel obstruction
Urinary retention (mechanical ischuria) or urinary-tract spasms
Myotonic dystrophy
Closed traumatic brain injuries
Depolarization block after depolarizing muscle relaxants
Intoxication with irreversible cholinesterase inhibitors, organophosphates (phosphoric acid esters), or barbiturates

Cautions

Life-threatening hypersensitivity reactions possible — keep emergency measures ready
Caution in diabetes, bradycardia, AV conduction disturbances, Parkinson's disease, ulcerative colitis
Cardiac arrest possible when used as TCA antidote — continuous ECG monitoring required

Adverse reactions

Cholinergic effects: hypersalivation, sweating, nausea/vomiting
Bradycardia/tachycardia, sinoatrial block, hypotension
Bronchospasm
Hypersensitivity reactions

Pregnancy No human experience; crosses placenta — use only if absolutely necessary.

Lactation Unknown if excreted in milk; use only if absolutely necessary.

Cost

Physostigmine (ANTILIRIUM)

Strength		#/mo	generic $/unit	CostPlus
0.4 mg/mL	inj	per unit		not offered
1 mg/mL	inj	per unit		not offered

NADAC is a voluntary CMS survey of what retail community pharmacies pay for the drugs they stock. Physostigmine is administered under clinical supervision and dispensed outside retail pharmacies, so it rarely appears on surveyed invoices.

Generic entryN/A – unapproved legacy product

NO BOXED WARNINGS

Principal riskbradyarrhythmia or seizure in sodium-channel-blocker toxicity

Classes and tags

Clinical profile

Therapeutic safety burden3 / 4

Overdose danger3 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryUnknown / historical label unavailable

Defining liabilityAgent-specific cardiovascular, neurologic or metabolic toxicity requires monitored use in poisoning or overload.

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