The possible use of oximes as antidotal therapy in organophosphate-induced brain damage

Organophosphate (OP) poisoning poses great danger to both military and civilian populations. OP-induced brain injury is characterized by rapid loss of consciousness, seizures, central respiratory inhibition as well as long-term behavioral changes in sub-lethal injuries. The pharmacological treatment of OP poisoning is based on anticholinergic and anticonvulsant drugs as well as oximes, which reactivate the non-aged inhibited enzyme. The commonly used oximes are quaternary compounds with questionable capacity to penetrate through the blood-brain barrier. This implies that the main beneficial effect of oximes may result from reactivation of AChE activity in respiratory muscles rather than in the brain. Importantly, data accumulated over the last few decades suggests a potential beneficial role for oximes in the brain, despite their polarity. Albeit the concentration of oximes in the central nervous system is significantly lower than in the plasma, they do gain access into the brain and are able to reactivate inhibited local AChE. Oximes may also attenuate OP-induced brain insult via different mechanisms other than AChE reactivation. In this review, we focus on the ability of oximes to act in the brain and protect the central nervous system from OP-induced injury, either by direct reactivation of AChE or by other pharmacological mechanisms. While this is a poorly investigated field we believe that the data supports the potential role of oximes in mitigating OP-induced neuronal injury, thus making them valuable in the treatment of severe casualties.