Oxime therapy and outcomes in human organophosphate poisoning: an evaluation using meta-analytic techniques.

OBJECTIVE: The status of oximes in human organophosphate poisoning is controversial. This analysis compares the outcomes of therapy with or without oximes.

DESIGN: Quantitative analysis using meta-analytic techniques.

METHODS: Controlled trials of oximes in human organophosphate poisoning were identified by search of MEDLINE and TOXLINE (1966 to May 2005) and review of published articles.

MEASUREMENTS AND MAIN RESULTS: Of the 3,122 articles on organophosphate poisoning identified by electronic search, 116 related to oxime use in human organophosphate poisoning. Seven trials, including two randomized controlled trials, compared oximes with standard medical care. Varying dosage schedules of pralidoxime or obidoxime were used. The effects of oxime therapy on mortality rate, mechanical ventilation, incidence of intermediate syndrome, and need for intensive care therapy were analyzed and expressed as risk difference (positive values indicating oxime harm). The random effects estimator was reported because of underlying heterogeneity of treatment effects between study types. No statistically significant association of oxime therapy was demonstrated for either mortality (risk difference 0.09, 95% confidence interval -0.08 to 0.27), ventilatory requirements (risk difference 0.16, 95% confidence interval -0.07 to 0.38), or the incidence of intermediate syndrome (risk difference 0.16, 95% confidence interval -0.12 to 0.45), although point estimates of effect suggested harm. An increased need for intensive care therapy (risk difference 0.19, 95% confidence interval 0.01 to 0.36) was apparent with oxime therapy.

CONCLUSIONS: Based on the current available data on human organophosphate poisoning, oxime was associated with either a null effect or possible harm. The lack of current prospective randomized controlled trials, with appropriate patient stratification, mandates ongoing assessment of the role of oximes in organophosphate poisoning.