title: Oximes for acute organophosphate pesticide poisoning.
abstract: BACKGROUND
  Acute organophosphorus pesticide poisoning causes tens of thousands of deaths each year across the developing world. Standard treatment involves administration of intravenous atropine and oxime to reactivate inhibited acetylcholinesterase. The clinical usefulness of oximes, such as pralidoxime and obidoxime, has been challenged over the past 20 years by physicians in many parts of the world.
  
  
  OBJECTIVE
  To quantify the effectiveness and safety of the administration of oximes in acute organophosphorus pesticide-poisoned patients.
  
  
  METHODS
  We searched both English and Chinese databases: Cochrane Injuries Group Specialised Register, Cochrane Central Register of Controlled Trials (The Cochrane Library), MEDLINE (Ovid SP), EMBASE (Ovid SP), ISI Web of Science: Science Citation Index Expanded (SCI-EXPANDED), ISI Web of Science: Conference Proceedings Citation Index-Science (CPCI-S) and the Chinese language databases CNKI and WANGFANG. All searches were run in September 2009.
  
  
  METHODS
  Articles that could possibly be RCTs were retrieved to determine if they were randomised.
  
  
  METHODS
  The published methodology of three RCTs was not clear. We contacted the principal authors of these, but did not obtain further information.
  
  
  RESULTS
  Seven pralidoxime RCTs were found. Three RCTs including 366 patients studied pralidoxime vs placebo and four RCTs including 479 patients compared two or more different doses. These trials found quite disparate results with treatment effects ranging from benefit to harm. However, many studies did not take into account several issues important for outcomes. In particular, baseline characteristics were not balanced, oxime doses varied widely, there were substantial delays to treatment, and the type of organophosphate was not taken into account. Only one RCT compared the World Health Organization (WHO) recommended doses with placebo. This trial showed no clinical benefits and a trend towards harm in all sub-groups, despite clear evidence that these doses reactivated acetylcholinesterase in the blood.
  
  
  CONCLUSIONS
  Current evidence is insufficient to indicate whether oximes are harmful or beneficial. The WHO recommended regimen (30 mg/kg pralidoxime chloride bolus followed by 8 mg/kg/hr infusion) is not supported. Further RCTs are required to examine other strategies and regimens. There are many theoretical and practical reasons why oximes may not be useful, particularly for late presentations of dimethyl OP and those with a large excess of OP that simply re-inhibits reactivated enzymes. Future studies should screen for patient sub-groups that may benefit and may need flexible dosing strategies as clinical effectiveness and doses may depend on the type of OP.
authors.affiliation: Professorial Medicine Unit, POWH Clinical School, University of NSW, South Wing, Edmund Blackett building, Prince of Wales Hospital, Randwick, NSW, Australia, 2031.
authors.forename: Nick A
authors.initials: NA
authors.lastname: Buckley
authors.forename: Michael
authors.initials: M
authors.lastname: Eddleston
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.forename: Marc
authors.initials: M
authors.lastname: Bevan
authors.forename: Jane
authors.initials: J
authors.lastname: Robertson
mesh_terms: D000931:Antidotes / Q000627:therapeutic use*; D002801:Cholinesterase Reactivators / Q000627:therapeutic use; D006801:Humans; D062025:Organophosphate Poisoning; D010091:Oximes / Q000627:therapeutic use*; D010575:Pesticides / Q000506:poisoning*; D011041:Poisoning / Q000188:drug therapy; D011220:Pralidoxime Compounds / Q000627:therapeutic use; D016032:Randomized Controlled Trials as Topic
chemical_list: D000931:Antidotes; D002801:Cholinesterase Reactivators; D010091:Oximes; D010575:Pesticides; D011220:Pralidoxime Compounds