A third clinical manifestation of OP toxicity, the so-called intermediate syndrome, should also be briefly discussed. The intermediate syndrome is characterized by weakness of respiratory, neck and proximal limb muscles [21]. It is not a direct effect of AChE inhibition, and appears several hours after the beginning of signs and symptoms of severe cholinergic over-stimulation, but before eventual signs of OPIDP (hence the name intermediate). The intermediate syndrome is seen in 20–50% of acute OP poisoning cases, where it develops during recovery from cholinergic manifestations. The underlying mechanisms are unknown, but an hypothesis is that muscle weakness may result from cholinergic receptor desensitization due to prolonged cholinergic stimulation [9].