ABSTRACT
The N-methyl carbamate esters cause reversible carbamylation of acetylcholinesterase enzyme, allowing accumulation of acetylcholine, neuromediator substance, at parasympathetic neuroeffector junctions, at skeletal muscle myoneural junctions and autonomic ganglia, and in the brain. N-Methyl carbamates are absorbed by inhalation and ingestion and some by skin penetration. Dermal absorption of particular compounds is very slight. The N-methyl carbamates are hydrolyzed enzymatically by the liver, and degradation products are excreted by the kidneys and the liver. Poisonings by N-methyl carbamates tend to be of shorter duration than poisonings by organophosphates, but they are not easily differentiated from organophosphate poisoning in acute phase, in the absence of an accurate exposure history. Absorption of some N-methyl carbamates can be confirmed by analysis of urine for unique metabolites: α-naphthol from carbaryl, isopropoxyphenol from propoxur, carbofuran phenol from carbofuran, aldicarb sulfone and nitrile from aldicarb. Severely poisoned individuals may exhibit remarkable tolerance to atropine; two or more times the dosages suggested in the foregoing may be needed.
