Measurement of serum pralidoxime methylsulfate (Contrathion®) by high-performance liquid chromatography with electrochemical detection

Pralidoxime methylsulfate (Contrathion®) is widely used to treat organophosphate poisoning. Despite animal and human studies, the usefulness of Contrathion® therapy remains a matter of debate. Therapeutic dosage regimens need to be clarified and availability of a reliable method for plasma pralidoxime quantification would be helpful in this process. We here describe a high-performance liquid chromatography technique with electrochemical detection to measure pralidoxime concentrations in human serum using guanosine as an internal standard. The assay was linear between 0.25 and 50 μg mL−1 with a quantification limit of 0.2 μg mL−1. The analytical precision was satisfactory, with variation coefficients lower 10%. This assay was applied to the analysis of a serum from an organophosphorate poisoned patient and treated by Contrathion® infusions (100 and 200 mg h−1) after a loading dose (400 mg).