Organophosphorus and Carbamate Insecticides

Organophosphorus (OP) and Carbamate insecticides are among the most widely used classes of pesticides, sharing a common mechanism of toxicity through acetylcholinesterase (AChE) inhibition. This topic is fundamental for Zambian college and university students in pharmacology, toxicology, and occupational health due to the high acute toxicity risk from exposure. Students will delve into the biochemistry of AChE inhibition: OPs cause irreversible phosphorylation of the enzyme's serine hydroxyl group, while carbamates cause reversible carbamylation. This leads to accumulation of acetylcholine at synapses, resulting in acute cholinergic crisis (muscarinic, nicotinic, and CNS effects). The topic also covers important differences, such as the potential for OP-induced delayed neuropathy (OPIDN) and the greater environmental lability of these compounds compared to organochlorines. Specific examples like malathion (lower mammalian toxicity) and parathion (high toxicity) are analyzed. Proficiency in this topic is essential for exam success and for the clinical diagnosis and management of pesticide poisoning, a common medical emergency in agricultural communities in Zambia.