Carbamate Poisoning and Oxime Treatment in Children: A Clinical and Laboratory Study

OBJECTIVE: (1) Retrospective evaluation of the clinical course of carbamate poisoning and the effect of oxime therapy in children. (2) In vitro study of the effect of oximes on the reactivation of carbamylated cholinesterase. DESIGN: (1) Clinical survey: The records of 26 children intoxicated with carbamates were examined retrospectively. The poisoning agents in all cases were positively identified as methomyl or aldicarb by gas chromatography-mass spectrometry. (2) Laboratory study: The direct effect of obidoxime and of pralidoxime on acetylcholinesterase activity in vitro was investigated in normal human packed red blood cells pretreated with an organophosphate (paraoxon) or a carbamate (aldicarb or methomyl). CLINICAL SETTING: Pediatric intensive care unit of a teaching hospital. PATIENTS: Twenty-six infants and young children (aged 1 to 8 years) admitted to the pediatric intensive care unit with severe carbamate intoxication. INTERVENTIONS: All cases had been treated with repeated doses of atropine sulfate (0.05 mg/kg) administered every 5 to 10 minutes until muscarinic symptoms disappeared. Obidoxime chloride (Toxogonin, 6 mg/kg) was administered on admission, and again after 4 to 5 hours. RESULTS: Predominant symptoms were related to central nervous system and nicotinic effects. All the patients showed marked improvement within several hours and recovered completely within 24 hours. None of the children deteriorated and none showed exacerbation of cholinergic symptoms after obidoxime treatment. In vitro, oximes reactivated acetylcholinesterase inhibited with paraoxon, whereas no significant effect of oximes on carbamylated enzyme activity was observed. CONCLUSIONS: Based on the recovery of all cases, as compared with other reports of carbamate poisoning treated with atropine alone, it is concluded that, in the case of aldicarb or methomyl poisoning, oxime therapy apparently does not contribute to the recovery of poisoned patients. In cases of poisoning by an unknown pesticide or of mixed poisoning, oxime therapy can prove beneficial because no negative effects of the therapy can be discerned.