Some clinicians assess the efficacy of pralidoxime in organophosphorus (OP) poisoned patients by measuring reactivation of butyrylcholinesterase (BCHE). However, the degree of BCHE inhibition varies by OP insecticide, and it is unclear how well oximes reactivate BCHE in vivo. We aimed to assess the usefulness of BCHE activity to monitor pralidoxime treatment by studying its reactivation after pralidoxime administration to patients with laboratory-proven World Health Organization (WHO) class II OP insecticide poisoning. Patient data were derived from 2 studies, a cohort study (using a bolus treatment of 1g pralidoxime chloride) and a randomized controlled trial (RCT) (comparing 2g pralidoxime over 20min, followed by an infusion of 0.5g/h, with placebo). Two grams of pralidoxime variably reactivated BCHE in patients poisoned by 2 diethyl OP insecticides, chlorpyrifos and quinalphos; however, unlike acetylcholinesterase reactivation, this reactivation was not sustained. It did not reactivate BCHE inhibited by the dimethyl OPs dimethoate or fenthion. The 1-g dose produced no reactivation. Pralidoxime produced variable reactivation of BCHE in WHO class II OP-poisoned patients according to the pralidoxime dose administered, OP ingested, and individual patient. The use of BCHE assays for monitoring the effect of pralidoxime treatment is unlikely to be clinically useful.
        
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Konickx LA, Worek F, Jayamanne S, Thiermann H, Buckley NA, Eddleston M (2013) Reactivation of Plasma Butyrylcholinesterase by Pralidoxime Chloride in Patients Poisoned by WHO Class II Toxicity Organophosphorus Insecticides Toxicol Sci136: 274-83