Intramuscular, Intravenous Reversal of anticholinergic effect
Adult: Initial: 0.5-2 mg via slow IV (1 mg/minute) or IM inj. May repeat every 10-30 minutes until desired response is achieved. Dose reduction, dosing interruption, or discontinuation may be required according to individual safety or tolerability (refer to detailed product guideline). Child: Initial: 0.02 mg/kg via slow IV (0.5 mg/minute) or IM inj. May repeat every 5-10 minutes until desired response is achieved. Max: 2 mg.
Contraindications
CV disease, diabetes, asthma, gangrene; gastrointestinal and genitourinary obstruction, or any vagotonic state. Concomitant use with choline esters (e.g. methacholine, bethanechol) and depolarizing neuromuscular-blocking agents (e.g. succinylcholine).
Special Precautions
Patient with seizure or bradycardia. Concomitant use with epileptogenic drugs. Children. Pregnancy and lactation.
Monitor ECG and vital signs. Assess for signs of cholinergic crisis during treatment.
Overdosage
Symptoms: Nausea, vomiting, diarrhoea, excessive salivation and sweating, miosis, bradycardia or tachycardia, hypotension or hypertension, severe muscle weakness, paralysis, confusion, seizures, coma and death (as a result of respiratory paralysis and/or pulmonary oedema). Management: Administer atropine sulfate 2-4 mg (adult); 1 mg (children) every 3-10 minutes until muscarinic effects are controlled.
Drug Interactions
May enhance the cholinergic effects of cholinergic agonists (e.g. bethanechol, methacholine). May increase the serum concentration of succinylcholine. May increase risk of seizures with epileptogenic drugs.
Action
Description: Mechanism of Action: Physostigmine is a reversible anticholinesterase derived from Calabar bean. It inhibits the action of acetylcholinesterase thereby prolonging the central and peripheral effects of acetylcholine. Onset: Within 3-8 minutes. Duration: Approx 45-60 minutes. Pharmacokinetics: Absorption: Readily absorbed from the gastrointestinal tract, subcutaneous tissues, and mucous membranes. Distribution: Distributed throughout the body. Crosses the blood-brain barrier. Metabolism: Metabolised via hydrolysis by cholinesterases. Excretion: Via urine (small amount). Elimination half-life: 1-2 hours.
Chemical Structure
Physostigmine Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 5983, Physostigmine. https://pubchem.ncbi.nlm.nih.gov/compound/Physostigmine. Accessed Aug. 26, 2021.
V03AB19 - physostigmine ; Belongs to the class of antidotes. Used in the management of noxious gases poisoning.
References
Anon. Physostigmine Salicylate. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 14/07/2021.Anon. Physostigmine. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 14/07/2021.Buckingham R (ed). Physostigmine. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 14/07/2021.Physostigmine Salicylate (Akorn, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 14/07/2021.
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