RESUMEN
Formamidines are pesticides used in veterinary with activity as acaricides and insecticides. Human poisoning with these products can cause a clinical presentation similar to an organophosphate-pesticide poisoning. This situation can induce errors in diagnosis, with inadequate treatment and toxic or adverse effects of antidotes. We stress the importance of a correct diagnosis in these cases. The cholinesterase dosification in blood allows the fast discard of oragnophosphate-pesticide poisoning. The possibility of detecting 3-methyl-4-aminobenzoic acid in urine be helphul for confirmation of diagnosis. Poisoning by formamidines requires only decontamination (if not many hours have elapsed, if the amount ingested is important, if the respiratory airway can be protected), and symptomatic and/or intensive care measures. Cardiac monitoring and mechanical ventilation might be required. In theory, the fast metabolism of the product allows a short-acting toxic effect. Special attention deserves the solvent, thay may contribute to depression of the central nervous system and might compromise the respiratory function