Citation

Chan TYK, Critchley JAJH. Hong Kong Practitioner 1998; 20(11): 604-613.

Copyright

(Copyright © 1998)

DOI

unavailable

PMID

unavailable

Abstract

There are two groups of widely used acetylcholinesterase (ACHE) inhibitor insecticides; the organophosphate insecticides (OPI) and the carbamates. They phosphorylate or carbamylate ACHE, causing irreversible or reversible inhibition of AChE respectively. Consequently the neurotransmitter; acetylcholine, accumulates at synapses. The clinical syndrome of cholinergic excess is more benign and lasts shorter with the carbamates. Unlike OPI, the carbamates penetrate the central nervous system (CNS) poorly. Thus, prominent CNS effects such as convulsions are rare with carbamate poisoning. In severe OPI poisoning (usually after intentional ingestion), respiratory support with timely endotracheal intubation and mechanical ventilation and antidotal therapy with atropine (in adequate dosage) and pralidoxime (best within 24-48 hours) are the mainstays of treatment. Some patients may develop the intermediate syndrome and peripheral neuropathy. Most patients with carbamate poisoning will recover spontaneously within 24 hours. Pralidoxime is therefore reserved for seriously poisoned patients. In Hong Kong, vegetable-borne methamidophos is the most important cause of acute insecticide poisoning. The symptoms of acetylcholine excess are largely gastrointestinal and relatively mild. Patients only require symptomatic treatment, such as anticholinergic drugs and antidiarrhoeal drugs. The best preventive measure is close surveillance of imported vegetables for methamidophos. Rinsing the vegetable under tap water or soaking it in water followed by cooking can remove substantial amounts of the methamidophos residues. Poisoning due to other OPI or carbamates are otherwise uncommon. Acute exposures are more often due to parasuicides than to accidents at work. Proper packaging, labelling, storage and handling of these chemicals are necessary to avoid accidental exposure at home or at work.

Language: en

Keywords

antidiarrheal agent; article; artificial ventilation; carbamate insecticide; cholinergic receptor blocking agent; endotracheal intubation; food contamination; human; intoxication; methamidophos; organophosphate insecticide; peripheral neuropathy; suicide attempt