Progression of intoxication and longer term risks

In cases of attempted suicide, often fatal intoxications occur where, in spite of early hospitalization, patients are beyond remedy. Initially, signs of recovery may be observed, but after 2-3 days patients relapse with a measurable increase in OP plasma concentrations. This phenomenon is called intermediary syndrome (IMS), first described by Senananyake et al. in 1987, and is possibly a consequence of a severe intoxication with permanent depolarization of the neuromuscular end-plates and constant excitation of the nicotinic acetylcholine receptors in the CNS of the patient. The IMS is clinically characterized by acute respiratory paresis, weakness of facial, palatal, external ocular, nuchal and proximal limb muscles and depressed tendon reflexes. Some authors propose that an insufficient therapy with oximes or atropine (see Section 9.2.5) and inadequate artificial respiration in the early stages of intoxication may cause the occurrence of an IMS. It is further remarkable that only some distinct OP agents (e.g. fenthion, dimethoate, monocrotophos and methamidophos) seem capable of producing the IMS. 

In spite of the extensive knowledge about different kinds of consequences of an intoxication with OP.v, data on toxic blood concentrations are non-existent for most of the substances. When known, the values vary strongly between the respective OP.v. For example, the toxic and comatose-fatal (see case report) blood concentrations of parathion are in the ranges 10-50 and 50-80 ng mf, respectively. In contrast, higher concentrations of 

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