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In poisoning with organophosphorus compounds (OP), patients can only profit from the regeneration of acetylcholinesterase, when the poison load has dropped below a toxic level. Every measure that allows an increase of synaptic acetylcholinesterase (AChE) activity at the earliest is essential for timely termination of the cholinergic crisis. Only drug-induced reactivation allows fast restoration of the inhibited AChE. Obidoxime and pralidoxime have proved to be able to reactivate inhibited cholinesterase thereby saving life of poisoned animals. A plasma level of obidoxime or pralidoxime allowing reactivation in humans poisoned by OP can be adjusted. There is no doubt that obidoxime and pralidoxime are able to reactivate OP-inhibited AChE activity in poisoned patients, thereby increasing AChE activity and contributing substantially to terminate cholinergic crisis. Hence, a benefit may be expected when substantial reactivation is achieved. A test system allowing determination of red blood cell AChE activity, reactivatability, inhibitory equivalents and butyrylcholinesterase activity is available for relatively low cost. If any reactivation is possible while inhibiting equivalents are present, oxime therapy should be maintained. In particular, when balancing the benefit risk assessment, obidoxime or palidoxime should be given as soon as possible and as long as a substantial reactivation may be expected.

International audience; Novel 6-alkyl- and 6-alkenyl-3-fluoro-2-pyridinaldoximes have been synthesised by using a mild and efficient chemoselective hydrogenation of 6-alkynyl-3-fluoro-2-pyridinaldoxime scaffolds, without altering the reducible, unprotected, sensitive oxime functionality and the C-F bond. These novel 6-alkyl-3-fluoro-2-pyridinaldoximes may find medicinal application as antidotes to organophosphate poisoning. Indeed, one low-molecular-weight compound exhibited increased affinity for sarin-inhibited acetylcholinesterase (hAChE) and greater reactivation efficiency or resurrection for sarin-inhibited hAChE, compared with those of 2-pyridinaldoxime (2-PAM) and 1-({[4-(aminocarbonyl)pyridinio]methoxy}methyl)-2-[(hydroxyimino)methyl]pyridinium chloride (HI-6), two pyridinium salts currently used as antidote by several countries. In addition, the uncharged 3-fluorinated bifunctional hybrid showed increased in vitro blood-brain barrier permeability compared with those of 2-PAM, HI-6 and obidoxime. These promising features of novel low-molecular-weight alkylfluoropyridinaldoxime open up a new era for the design, synthesis and discovery of central non-quaternary broad spectrum reactivators for organophosphate-inhibited cholinesterases.

A novel series of 30 symmetric bispyridinium and related N-heteroaromatic bisquaternary salts with a propane-1,3-diyl linker was synthesized and characterized for their binding affinity at the MB327 binding site of nicotinic acetylcholine receptor (nAChR) from Torpedo californica. Compounds targeting this binding site are of particular interest for research into new antidotes against organophosphate poisoning, as therapeutically active 4-tert-butyl-substituted bispyridinium salt MB327 was previously identified as a nAChR re-sensitizer. Efficient access to the target compounds was provided by newly developed methods enabling N-alkylation of sterically hindered or electronically deactivated heterocycles exhibiting a wide variety of functional groups. Determination of binding affinities toward the MB327 binding site at the nAChR, using a recently developed mass spectrometry (MS)-based Binding Assay, revealed that several compounds reached affinities similar to that of MB327 (pK(i)=4.73 +/- 0.03). Notably, the newly prepared lipophilic 4-tert-butyl-3-phenyl-substituted bispyridinium salt PTM0022 (3h) was found to have significantly higher binding affinity, with a pK(i) value of 5.16 +/- 0.07, thus representing considerable progress toward the development of more potent nAChR re-sensitizers.

Despite the main mechanism of organophosphate (OP) toxicity through inhibition of acetylcholinesterase (AChE) being well known over the years, some chronic adverse health effects indicate the involvement of additional pathways. Oxidative stress is among the most intensively studied. Overstimulation of cholinergic and glutamatergic nervous system is followed by intensified generation of reactive species and oxidative damage in many tissues. In this review, the role of oxidative stress in pathophysiology of OP poisoning and the influence of commonly used medical interventions on its levels are discussed. Current standardized therapy of OP intoxications comprises live-saving administration of the anticholinergic drug atropine accompanied by oxime AChE reactivator and diazepam. The capability of these antidotes to ameliorate OP-induced oxidative stress varies between both therapeutic groups and individual medications within the drug class. Regarding oxidative stress, atropine does not seem to have a significant effect on oxidative stress parameters in OP poisoning. In a case of AChE reactivators, pro-oxidative and antioxidative properties could be found. It is assumed that the ability of oximes to trigger oxidative stress is rather associated with their chemical structure than reactivation efficacy. The data indicating the potency of diazepam in preventing OP-induced oxidative stress are not available. Based on current knowledge on the mechanism of OP-mediated oxidative stress, alternative approaches (including antioxidants or multifunctional drugs) in therapy of OP poisoning are under consideration.

The influence of three newly-developed bispyridinium antinicotinic compounds (the non-oximes MB408, MB442 and MB444) on the therapeutic efficacy of a standard antidotal treatment (atropine in combination with an oxime) of acute poisoning by the organophosphorus nerve agents tabun and soman was studied in mice. The therapeutic efficacy of atropine in combination with an oxime with or without one of the bispyridinium non-oximes was evaluated by determination of the LD50 values of the nerve agents and measurement of the survival time after supralethal poisoning. Addition of all the tested non-oximes increased significantly the therapeutic efficacy of atropine in combination with an oxime against tabun poisoning. They also positively influenced the number of surviving mice 6 hr after supralethal poisoning with tabun. However, they were only slightly effective for the treatment of soman poisoning. The benefit of the tested bispyridinium non-oximes was dose-dependent. To conclude, the addition of bispyridinium non-oximes to the standard antidotal treatment of acute poisoning with tabun was beneficial regardless of the chosen non-oxime, but only slightly beneficial in the case of soman poisoning. This article is protected by copyright. All rights reserved.

BACKGROUND Previous epidemiological studies investigating modification of organophosphate (OP) neurotoxicity by xenobiotic metabolizing enzymes (XMEs) polymorphisms have produced inconsistent results. METHODS A cross-sectional study of 301 emerging farmers was conducted. Neurotoxicity testing included forward and backward recall, digit span, and vibration sensitivity testing. Questionnaire data included demography, potential confounders, and work history of pesticide exposures. Genomic DNA was analyzed from study participants for DNA variants of two glutathione S-transferases (GSTM1 and GSTT1), N-acetyltransferase 2 (NAT2), and Paraoxonase 1 (PON1). RESULTS There was evidence of OP pesticide neurotoxicity modification by rs1799931 (NAT2), rs662 (PON1), and the null allele of GSTM1 in multivariate analysis. The strongest evidence of modification was observed for rs1799931 (NAT2) on the relationship between pesticide poisoning and impaired vibration sense. CONCLUSIONS DNA variants of NAT2, PON1, and GSTM1 may modify OP neurotoxicity, and this requires further exploration.

Background To assess the usefulness of serum C‐terminal hydrolase L1 (UCH‐L1) level as a biomarker for predicting cognitive impairment in patients with acute organophosphorus pesticide poisoning (AOPP). Methods Two hundred and seven adult patients with AOPP were included in this study. Serum UCH‐L1 levels were assessed on admission (Day 1 postpoisoning) and on Days 3 and 7 postpoisoning. The associations between serum UCH‐L1 levels, other clinical predictors, and cognitive function evaluated on Day 30 postpoisoning were investigated. Results On multivariate analysis, serum UCH‐L1 levels on admission (odds ratio [OR] 1.889, 95% confidence interval [CI] 1.609‐3.082, P = 0.002) and 24‐hour APACHE II score (OR 1.736, 95% CI 1.264‐3.272, P = 0.012) were independent predictors of cognitive impairment on Day 30 postpoisoning. Based on the receiver operating characteristic curve, serum UCH‐L1 levels >5.9 ng/mL on admission predicted cognitive impairment on Day 30 postpoisoning with 86.1% sensitivity and 72.5% specificity (area under the curve, 0.869; 95% CI 0.815‐0.923). On admission [8.51 (6.53‐10.22) ng/mL vs 4.25 (2.57‐6.31) ng/mL, P

Organophosphates are phosphorus containing compounds that inhibit acetylcholinesterase and generate a cholinergic crisis that is fatal if not treated. The classical antidotes prescribed are atropin...

Irreversible inhibition of the essential nervous system enzyme acetylcholinesterase by organophosphate nerve agents and pesticides may quickly lead to death. Oxime reactivators currently used as antidotes are generally less effective against pesticide exposure than nerve agent exposure, and pesticide exposure constitutes the majority of cases of organophosphate poisoning in the world. The current lack of published structural data specific to human acetylcholinesterase organophosphate-inhibited and oxime-bound states hinders development of effective medical treatments. We have solved structures of human acetylcholinesterase in different states in complex with the organophosphate insecticide, paraoxon, and oximes. Reaction with paraoxon results in a highly perturbed acyl loop that causes a narrowing of the gorge in the peripheral site that may impede entry of reactivators. This appears characteristic of acetylcholinesterase inhibition by organophosphate insecticides but not nerve agents. Additional changes seen at the dimer interface are novel and provide further examples of the disruptive effect of paraoxon. Ternary structures of paraoxon-inhibited human acetylcholinesterase in complex with the oximes HI6 and 2-PAM reveals relatively poor positioning for reactivation. This study provides a structural foundation for improved reactivator design for the treatment of organophosphate intoxication. Proteins 2016; 84:1246-1256. © 2016 Wiley Periodicals, Inc.

Organophosphorus (OP) pesticide poisoning is a leading cause of morbidity and mortality in the developing world, affecting an estimated three million people annually. Much of the morbidity is directly related to muscle weakness, which develops 1-4 days after poisoning. This muscle weakness, termed the intermediate syndrome (IMS), leads to respiratory, bulbar, and proximal limb weakness and frequently necessitates the use of mechanical ventilation. While not entirely understood, the IMS is most likely due to persistently elevated acetylcholine (ACh), which activates nicotinic ACh receptors at the neuromuscular junction (NMJ). Thus, the NMJ is potentially a target-rich area for the development of new therapies for acute OP poisoning. In this manuscript, we discuss what is known about the IMS and studies investigating the use of nicotinic ACh receptor antagonists to prevent or mitigate NMJ dysfunction after acute OP poisoning.

In cases of organophosphate poisoning, patients are treated with a combination of antidotes. In addition to these poison-directed antidotes, patients may require extra oxygen and artificial ventilation; other modalities may also be needed due to the wide range of toxic effects. Anisodamine is a belladonna alkaloid, and like other drugs from this family is non subtype-selective muscarinic, and a nicotinic cholinoceptor antagonist, which has been employed in traditional Chinese medicine. As a muscarinic antagonist, it displays similar pharmacological effects to atropine and scopolamine. However, anisodamine is not only less potent than atropine and scopolamine but also less toxic. Current in vitro and animal model studies have demonstrated that anisodamine has protective effects in a variety of diseases. Organophosphate poisoning involves not only the central and peripheral nervous systems, but also the cardiac and respiratory systems, as well as activation of inflammatory processes and oxidative stress. Therefore, the anticholinergic and additional activities of anisodamine appear to be relevant and justify its consideration as an addition to the existing remedies. However, more research is needed, as at present data on the role of anisodamine in the management of organophosphate poisoning are limited. Here, we review the beneficial effects of anisodamine on processes relevant to organophosphate poisoning.

Despite being a major clinical and public health problem across the developing world, responsible for at least 5 million deaths over the last three decades, the clinical care of patients with organophosphorus (OP) insecticide poisoning has little improved over the last six decades. We are still using the same two antidotes - atropine and oximes - that first came into clinical use in the late 1950s. Clinical research in South Asia has shown how improved regimens of atropine can prevent deaths. However, we are still unsure about which patients are most likely to benefit from the use of oximes. Supplemental antidotes, such as magnesium, clonidine and sodium bicarbonate, have all been proposed and studied in small trials without production of definitive answers. Novel antidotes such as nicotinic receptor antagonists, beta-adrenergic agonists and lipid emulsions are being studied in large animal models and in pilot clinical trials. Hopefully, one or more of these affordable and already licensed antidotes will find their place in routine clinical care. However, the large number of chemically diverse OP insecticides, the varied poisoning they produce and their varied response to treatment might ultimately make it difficult to determine definitively whether these antidotes are truly effective. In addition, the toxicity of the varied solvents and surfactants formulated with the OP active ingredients complicates both treatment and studies. It is possible that the only effective way to reduce deaths from OP insecticide poisoning will be a steady reduction in their agricultural use worldwide.

This paper reviews the blood-brain barrier (BBB) penetration of newly developed pyridinium aldoximes. Pyridinium aldoximes are highly charged hydrophilic compounds used in the treatment of subjects exposed to organophosphonates because they are effective as acetylcholinesterase reactivators. Pyridinium aldoximes have antidotal effects against poisoning with cholinesterase inhibitors, a frequent problem affecting people working with organophosphate-based insecticides and pesticides. Toxic organophosphonate products such as sarin and tabun can be used by terrorists as chemical warfare agents. This poses a severe challenge to all innocent and peace-loving people worldwide. This review gives a brief summary of BBB transporters and description of the current in vitro and in vivo methods for the characterization of BBB penetration of established and novel pyridinium aldoximes. The authors provide a putative mechanism of penetration, outline some future ways of formulation and discuss the possible advantages and disadvantages of increasing BBB penetration.

Acute severe organophosphate poisoning is a serious complication seen in developing and agricultural countries. Pralidoxime and high dose atropine are the standard treatments. There is no consensus about acute severe organophosphate poisonings that are unresponsive to pralidoxime, atropine, and supportive therapies. We report a case of acute severe organophosphate poisoning that was unresponsive to standard treatments and successfully treated with high-volume continuous venovenous hemodiafiltration and therapeutic plasma exchange combined with lipid infusion. J. Clin. Apheresis 31:467-469, 2016. © 2015 Wiley Periodicals, Inc.

K048 is a member of K-oximes, a new oxime class that has recently been confirmed effective against poisoning by the nerve agent tabun and several pesticides. The toxicity profile of the K048 oxime has not been fully characterized and its optimal therapeutic dose has not yet been established. Earlier studies report excellent results with K048 in reactivating tabun-phosphorylated AChE and in the therapy of tabun-poisoned mice. It possesses a low acute toxicity and exerts an acceptable toxicity profile on isolated human peripheral blood lymphocytes in vitro. Intraperitoneal administration of K048 in rats resulted in an LD50 of 238.3 mg/kg. In this in vivo study, we investigated cholinesterase (ChE) activity and oxidative stress marker levels (lipid peroxidation and superoxide dismutase activity) in the plasma of exposed rats after administering the compound at 25% of its LD50. Lymphocyte viability was evaluated using an acridine orange/ethidium bromide in situ fluorescent assay. The levels of primary DNA damage in rat white blood cells were measured using the alkaline comet assay. The compound applied at 25% of its LD50 did not significantly affect ChE activity and lipid peroxidation and did not cause significant changes in the SOD activity in plasma. The cytotoxicity profile of K048 in the tested dose was also acceptable, and it did not possess significant DNA-damaging potential. The obtained results are promising for further evaluations of the K048 oxime, which should include tests on a broader concentration range and longer incubation times.

Self-poisoning with pesticides or plants is a major clinical problem in rural Asia, killing several hundred thousand people every year. Over the last 17 years, our clinical toxicology and pharmacology group has carried out clinical studies in the North Central Province of Sri Lanka to improve treatment and reduce deaths. Studies have looked at the effectiveness of anti-digoxin Fab in cardiac glycoside plant poisoning, multiple dose activated charcoal in all poisoning, and pralidoxime in moderate toxicity organophosphorus insecticide poisoning. More recently, using a Haddon matrix as a guide, we have started conducting public health and animal studies to find strategies that may work outside of the hospital. Based on the 2009 GSK Research in Clinical Pharmacology prize lecture, this review shows the evolution of the group's research from a clinical pharmacology approach to one that studies possible interventions at multiple levels, including the patient, the community and government legislation.

Inhibition of acetylcholinesterase (AChE) is the main mechanism of action of organophosphorus compounds (OP), and AChE reactivators (oximes) are at present the only causal therapeutic approach. Being the key target of OP toxicity, AChE may serve as a valuable tool for diagnosis of OP exposure as well as for the investigation of the kinetics of interactions between OP and oximes. At present, the rapid, simple, and cheap spectrophotometric Ellman assay is widely used for diagnosis, therapeutic monitoring and in vitro kinetic investigations. Application of the assay for investigation of the interactions between AChE, inhibitors, and oximes requires the consideration of potential matrix effects (e.g. hemoglobin), side reactions (e.g. oximolysis of substrate) and other determinants (e.g. pH, temperature). By taking these factors into account, the Ellman assay allows the precise and reproducible determination of kinetic constants as a basis for the understanding of toxic OP effects and for the development of improved therapies against poisoning by OP. In addition, advanced applications of the Ellman assay, for example, in a dynamic in vitro model for the real-time activity determination of membrane-bound AChE, enables the proper investigation of relevant tissue, primarily respiratory muscle, and extends the applicability of this method.

S-hyoscyamine (S-hyo) is a natural plant tropane alkaloid acting as a muscarinic receptor (MR) antagonist. Its racemic mixture (atropine) is clinically used in pre-anaesthesia, ophthalmology and for the antidotal treatment of organophosphorus (OP) poisoning with nerve agents or pesticides even though R-hyo exhibits no effects on MR. Further investigative research is required to optimize treatment of OP poisoning. Swine are often the animal model utilized due to similarities in physiology and antidote response to humans. However, no studies have been reported that elucidated differences in the kinetics of R- and S-hyo. Therefore, the concentration-time profiles of total hyo as well as both enantiomers were analyzed in plasma after intravenous administration of atropine sulfate (Atr(2) SO(4) , 100 µg/kg) to anaesthetized swine. For quantification plasma samples were incubated separately with human serum (procedure A) and rabbit serum (procedure B). The rabbit serum used contained atropinesterase, which is suitable for stereoselective hydrolysis of S-hyo, while human serum does not hydrolyze either enantiomer. After incubation samples were precipitated and the supernatant was analyzed by RP-HPLC-ESI MS/MS. Procedure A allowed determination of total hyo and procedure B remaining R-hyo concentrations. S-hyo was calculated as the difference of the two procedures. Concentration data were regressed by a two-phase decay according to a two-compartment open model revealing similar kinetics for both enantiomers thus indicating distribution, metabolism and elimination without obvious stereoselective preference in tested swine.

The present paper reports on a 68-year-old man with a 10-year history of parkinsonism who developed hallucinations and delusions after admission to an intensive care unit for the treatment of organophosphate intoxication. His initial diagnosis was delirium. On the basis of brain computed tomography findings and clinical symptoms, we diagnosed drug-induced psychosis in parkinsonism with multiple cysts in the bilateral striata.

BACKGROUND AND PURPOSE Treatment of organophosphate poisoning with pralidoxime needs to be improved. Here we have studied the pharmacokinetics of pralidoxime after its intramuscular injection alone or in combination with avizafone and atropine using an auto-injector device. EXPERIMENTAL APPROACH The study was conducted in an open, randomized, single-dose, two-way, cross-over design. At each period, each subject received either intramuscular injections of pralidoxime (700 mg), or two injections of the combination: pralidoxime (350 mg), atropine (2 mg), avizafone (20 mg). Pralidoxime concentrations were quantified using a validated LC/MS-MS method. Two approaches were used to analyse these data: (i) a non-compartmental approach; and (ii) a compartmental modelling approach. KEY RESULTS The injection of pralidoxime combination with atropine and avizafone provided a higher pralidoxime maximal concentration than that obtained after the injection of pralidoxime alone (out of bioequivalence range), while pralidoxime AUC values were equivalent. Pralidoxime concentrations reached their maximal value earlier after the injection of the combination. According to Akaike and to goodness of fit criteria, the best model describing the pharmacokinetics of pralidoxime was a two-compartment with a zero-order absorption model. When avizafone and atropine were injected with pralidoxime, the best model describing pralidoxime pharmacokinetics becomes a two-compartment with a first-order absorption model. CONCLUSIONS AND IMPLICATIONS The two approaches, non-compartmental and compartmental, showed that the administration of avizafone and atropine with pralidoxime results in a faster absorption into the general circulation and higher maximal concentrations, compared with the administration of pralidoxime alone.

Contrary to the large number of publications dealing with treatment of organophosphate poisoning in a variety of animal species, there is no logic reason in the preference of one species, for this purpose. Guinea pigs were reported to respond better to treatment by oximes, than mice and rats. However, in the analysis of data on the effect of obidoxim and atropine or benactyzine on sarin poisoning it is demonstrated, that guinea pigs do not respond differently from mice and rats. Subcutaneous LD50's of sarin in mice ranged from 0.06 to 0.207 mg/kg, and those of guinea pigs from 0.04 to 0.112 mg/kg. The difference in the LD50's may be related to the different susceptibility of various animal species. The importance of "in vivo" dosage, mode of application, kinetics of antagonists, in correlation to the ability to reactivate "in vitro" is discussed.

The neuroprotective effects of newly developed oximes (K206, K269) and currently available oximes (obidoxime, HI-6) in combination with atropine in rats poisoned with cyclosarin were studied. The cyclosarin-induced neurotoxicity was monitored using a functional observational battery at 24 hr following cyclosarin challenge. The results indicate that a newly developed oxime K206 is able to counteract cyclosarin-induced neurotoxicity while the neuroprotective potency of another newly developed oxime (K269) is negligible. The neuroprotective efficacy of K206 is markedly higher than commonly used obidoxime; nevertheless, its potency to eliminate cyclosarin-induced neurotoxicity is slightly lower compared to the oxime HI-6. Thus, a newly developed oxime K206 seems to be a better oxime for the antidotal treatment of cyclosarin poisonings than obidoxime due to higher neuroprotective potency although the oxime HI-6 is still the most suitable oxime for the antidotal treatment of acute poisonings with cyclosarin.

Butyrylcholinesterase (BuChE) is routinely measured to assess exposure to or effects of organophosphorus insecticides (OP). As a biomarker, it can be used to clarify the relation between exposure to OP and health impairment. The interpretation of BuChE inhibition data, particularly of small changes in enzymatic activity, sometimes presents significant complexities. These complexities are presented in this short communication and the factors that influence the degree of BuChE inhibition are discussed. Despite the complexities of their interpretation, BuChE measurements remain a mainstay for the fast initial screening of exposure to OP; thus, they are a useful tool in the protection of humans, domestic animals and wildlife from overexposure to these toxic agents.

Therapeutically valuable proteins are often rare and/or unstable in their natural context, calling for production solutions in heterologous systems. A relevant example is that of the stress-induced, normally rare, and naturally unstable "read-through" human acetylcholinesterase variant, AChE-R. AChE-R shares its active site with the synaptic AChE-S variant, which is the target of poisonous organophosphate anticholinesterase insecticides such as the parathion metabolite paraoxon. Inherent AChE-R overproduction under organophosphate intoxication confers both short-term protection (as a bioscavenger) and long-term neuromuscular damages (as a regulator). Here we report the purification, characterization, and testing of human, endoplasmic reticulum-retained AChE-R(ER) produced from plant-optimized cDNA in Nicotiana benthamiana plants. AChE-R(ER) purified to homogeneity showed indistinguishable biochemical properties, with IC50 = 10(-7) M for the organophosphate paraoxon, similar to mammalian cell culture-derived AChE. In vivo titration showed dose-dependent protection by intravenously injected AChE-R(ER) of FVB/N male mice challenged with a lethal dose of paraoxon, with complete elimination of short-term clinical symptoms at near molar equivalence. By 10 days postexposure, AChE-R prophylaxis markedly limited postexposure increases in plasma murine AChE-R levels while minimizing the organophosphate-induced neuromuscular junction dismorphology. Our findings present plant-produced AChE-R(ER) as a bimodal agent, conferring both short- and long-term protection from organophosphate intoxication.

Organophosphate poisoning is a common cause of severe morbidity and mortality among patients admitted to emergency departments. Tissue damages as a consequence of organophosphate poisoning are frequently reported, but preventing this potentially severe complication has not been the subject of much research. We tested whether interleukin-10, a cytoprotective agent, could prevent or diminish pathological signs of tissue damages caused by organophosphate poisoning. Thirty rats were divided into three equal groups (n = 10). Group I (sham) did not receive any agent during the experiment. Group 2 (control) received 0.8 g/kg of fenthion intraperitoneally, followed by 6 ml/kg of intraperitoneal normal saline 30 min. and 3 hr later. Group 3 (treatment) received 0.8 g/kg of fenthion intraperitoneally, followed by 2 mu g/kg of interleukin- 10 intraperitoneally 30 min. and 3 hr later. All rats were killed under anaesthesia after 6 hr and tissue samples were obtained from liver, kidneys and lungs. Even organophosphate poisonings do not cause significant clinical problems; several degrees of damages could be observed in liver, kidneys and lungs. These damages could be reduced by interleukin-10 treatment.

In this prospective case series study, we consider the different factors between death and survival groups of organophosphate poisoning. Patients in tertiary-care medical center who had been exposed to organophosphate were included in the study. Pralidoxime (PAM) was discontinued after atropine had controlled the clinical situation. We recorded the demographic data, amount of organophosphate consumption, duration of coma, duration of ventilator use, duration of hospitalization, findings of chest X-ray, white blood cell count, acetylcholinesterase concentration, plasma cholinesterase concentration, total atropine amount, duration of atropine use, total PAM amount, duration of PAM use, urine organophosphate peak concentration, duration of urine organophosphate and mortality rate. Urine was collected every 8 hours and was analyzed by gas chromatography equipped with a flame photometric detector and gas chromatography with mass spectrometer detector for organophosphate determination. The urine organophosphate peak concentration was recorded. Wilcoxon rank sum test was used to compare the factors between death and survival groups. Fisher's exact test was used to compare the different findings of chest X-ray between the death and survival groups. Evidently, the death group had a higher amount of organophosphate consumption, duration of coma, and higher white blood cell count than those in the survival group. Also, the death group had lower duration of hospitalization, and decreased concentrations of acetylcholinesterase and plasma cholinesterase. Total PAM amount use and duration of PAM use were lower. However, the duration of ventilator use, findings of chest X-ray, total atropine amount, duration of atropine, urine organophosphate peak concentration and duration of urine organophosphate were similar in both groups. The mortality rate of our 50 cases was 20%. As stated earlier, the cases of the death group had insufficient PAM therapy. The maximum duration of PAM use was shorter than the maximum duration of urine organophosphate, although the medians of duration of PAM use were more than the medians of duration of urine organophosphate in both the survival and death groups. Prolonged coma duration, lower level of acetylcholinesterase and lower level of plasma cholinesterase were related to the poor prognosis of the patients.

Summary Organophosphate insecticides are widely used agents which are quickly absorbed through the skin and mucous membranes. The effects of acute exposure to these agents can be severe and intensive therapy may be required. Specific drugs are available to reverse the muscarinic, nicotinic and central effects of these poisons. When given early they are very effective and early diagnosis and treatment may therefore be life-saving. A case of acute poisoning with an organophosphate anticholinesterase insecticide is reported. The signs and symptoms of acute poisoning are described and a rational approach to specific treatment is discussed.

The neuroprotective effects of newly developed oximes (K074, K075) and currently available oximes (obidoxime, HI-6) in combination with atropine in rats poisoned with cyclosarin were studied. The cyclosarin-induced neurotoxicity was monitored using a functional observational battery at 24 h and 7 days following cyclosarin challenge. The results indicate that the oxime HI-6 combined with atropine seems to be the most effective antidote for a decrease in cyclosarin-induced neurotoxicity. Both newly developed oximes (K074, K075) as well as obidoxime are also able to counteract cyclosarin-induced acute neurotoxicity, but their neuroprotective potency is significantly lower compared with the oxime HI-6. Therefore, the oxime HI-6 is still the most suitable oxime for the antidotal treatment of acute poisonings with cyclosarin due to its neuroprotective as well as reactivating efficacy.

Immediate administration of antidotal treatment is crucial in severe organophosphate (OP) poisoning and the use of an open intravenous (i.v.) line might also be required. The state of casualties might prevent getting access to their veins. The bone injection gun (BIG) was established as a simple method for introducing an intraosseous (i.o.) line and could be applied while wearing a protective suit. The present study followed the pharmacokinetics of the anticonvulsive drug midazolam after i.o. administration in pigs compared with i.v. and the common intramuscular (i.m.) administration. A new method for monitoring midazolam concentrations in plasma was developed. Plasma concentrations following both i.v. and i.o. administrations peaked at 2 min post injection and only at 10 min following the i.m. route. In an antidotal treatment study against paraoxone poisoning, the anticonvulsive effect of midazolam appeared immediately following i.o. administration, while it took 5–10 min to exhibit a similar effect following i.m. administration. This study indicates that the use of i.o. administration after OP poisoning might provide the necessary fast response for rapid termination of convulsions. The BIG might offer a convenient method for treating casualties in the chemical arena by teams wearing full protective gear. Copyright © 2007 John Wiley & Sons, Ltd.

The development of effective antidotes against organophosphates such as dichlorvos has been a persistent challenge over the past decades. Therapy of organophosphate poisoning is based on the administration of atropine and oxime as standard antidotes. The present study was undertaken to evaluate the ability of sodium bicarbonate to improve protective effects of standard antidotes in rats poisoned with dichlorvos. The aim of this experiment was to establish the correlation between protective effects and biochemical parameters relevant for acid-base status. In order to examine the protective effect of both standard antidotes and their combinations, groups of experimental animals were poisoned subcutaneously with increasing doses of dichlorvos. Immediately thereafter, rats were treated with atropine 10 mg/kg intramuscularly, oximes 10 mg/kg intramuscularly and sodium bicarbonate 3 mmol/kg intraperitoneally. These antidotes were administered either as single doses or in combinations. In the biochemical part of the experiments, rats were poisoned with dichlorvos 1.3 LD50 (10.64 mg/kg) subcutaneously and immediately thereafter treated with atropine 10 mg/kg intramuscularly, oximes (trimedoxime or obidoxime) 10 mg/kg intramuscularly and sodium bicarbonate 3 mmol/kg intraperitoneally either as single doses or in combinations. Parameters relevant for acid-base status were measured 10 minutes after the administration of antidotes. The results of our study indicate that addition of sodium bicarbonate to standard antidotes significantly improves protective effects of atropine, obidoxime and trimedoxime. Correlation between protection and biochemical outcome is clearly evident when sodium bicarbonate is being added to atropine.

1. Pesticide poisoning kills hundreds of thousands of people in the Asia-Pacific region each year. The majority of deaths are from deliberate self-poisoning with organophosphorus pesticides (OP), aluminium phosphide and paraquat. The current response from a public health, medical and research perspective is inadequate. 2. There are few proven or effective treatments; in addition, very little clinical research has been performed to transfer antidotes shown to work in animal studies into clinical practice. 3. The human toxicity of pesticides is poorly studied and better information may inform a more sustained and appropriate regulatory response. Further understanding may also lead to improvements in diagnosis and treatment. 4. The few effective treatments are not being recommended or delivered in an optimal and timely fashion to poisoned patients. A regional approach to facilitate appropriate pricing, packaging and delivery of antidotes is required.

Objective: To discuss a new clinical presentation of organophosphate toxicity called the intermediate syndrome in a dog. Case summary: A mixed breed dog presented with generalized weakness, hypoventilation and hypoxemia. The weakness was most marked in the thoracic limbs, cervical and respiratory muscles. The history revealed a likely exposure to an organophosphate compound. The other dog in the household demonstrated mild clinical signs of organophosphate toxicity. A blood cholinesterase level was markedly reduced. Therapy included placement of a tracheostomy tube and mechanical ventilation. The dog gradually improved over the following 8 days but had persistent cervical ventroflexion for a total of 4 weeks. New or unique information provided: Organophosphate toxicity can present as a paralysis following the acute cholinergic crisis. The muscular weakness predominantly affects the thoracic limb and neck muscles but cranial nerve deficits can also occur. Dogs can die from the associated respiratory depression. Oxime therapy is indicated in the treatment of this syndrome.

Protection efficacy of continuous prophylactic administration of physostigmine and scopolamine against sarin-induced toxicity was evaluated previously in guinea pigs. The present study in large animals used Beagle dogs, that serve as an animal model with cholinergic sensitivity similar to that of humans. Pretreatment with physostigmine salicylate and scopolamine hydrochloride at dose rates of 2.5 and 1 microg x kg(-1) x h(-1), respectively, was administered via Alzet mini-osmotic pumps. At the time of exposure, the physostigmine salicylate concentration in plasma was 0.7 ng x ml(-1) and the scopolamine hydrochloride concentration was ca. 0.2 ng x ml(-1), both of which are levels known to be well tolerated in humans. Whole-blood cholinesterase inhibition was 15-20%. This regimen conferred full protection against 2.5 x LD50 i.v. of sarin. Albeit the high-dose exposure, cholinergic toxicity symptoms were mild with no convulsions. About 11-14 min following poisoning the treated animals started to walk and 15-20 min following exposure full recovery was observed and the dogs behaved normally. With higher dose rates of physostigmine salicylate and scopolamine hydrochloride, at plasma concentrations of 2.1 and 0.6 ng x ml(-1), respectively, treated dogs regained normal posture 6-10 min after exposure.

Nerve agents (NA) present a major threat to civilian populations. When a ballistic system is used for spreading poison, multiple trauma, as well as toxic trauma could be caused. Children are more susceptible, due to their smaller physiological reserve. Urgent surgical intervention for combined intoxication in the multiple-traumatized child could be a tremendous task in view of the background of physiological instability. Nerve agents affect the autonomic, as well as the central nervous system, leading occasionally to unexpected interactions with agents normally used for resuscitation. This can cause additional instability, and possibly systemic collapse. This review presents and emphasizes points concerning treatment of a child who suffers from combined multiple and toxic traumas. The review is based on scant knowledge of a database of similar cases of pesticide organophosphate poisoning in children since these compounds are alike. We also extrapolated data from reports concerning episodic civilian exposure to NA.

Phrenic nerve conduction studies were performed within 48 h of admission and subsequently in 29 patients (14 of whom required mechanical ventilation) with acute organophosphate (OP) poisoning. The mean (+/-SD) amplitude of the diaphragmatic compound muscle action potential (CMAP) in patients requiring mechanical ventilation (119.09 +/- 173.85 microV) was significantly lower than in those not requiring mechanical ventilation (461.63 +/- 138.69 microV) (P < 0.0001). Diaphragmatic CMAP amplitudes in ventilated patients increased with time during the course of hospitalization and were normal in 5 (36%) patients and only mildly reduced in another 6 (43%) patients prior to discontinuation of mechanical ventilation, which was undertaken 4-18 days (mean 7 +/- 3 days) after poisoning. Eleven patients (79%) were successfully weaned from mechanical ventilation at the first attempt. In the 3 (21%) remaining patients, mechanical ventilation had to be reestablished because of weaning failure. The mean (+/-SD) diaphragmatic CMAP amplitude, prior to discontinuation of ventilatory assistance, was 242.6 +/- 94.1 microV in these 3 patients. After ventilatory discontinuation, it fell to 95.5 +/- 105.8 microV. Thus, reduced diaphragmatic CMAP amplitudes correlate with the need for mechanical ventilation in acute OP poisoning.

Organophosphorus compounds, used as insecticides and agents of chemical warfare, are a major global cause of health problems. These irreversible inhibitors of cholinesterase produce three well-recognised clinical entities: the initial cholinergic phase, which is a medical emergency often requiring management in an intensive care unit; the intermediate syndrome, during which prolonged ventilatory care is necessary; and delayed polyneuropathy. In addition, disturbances of body temperature and endocrine function, electrolyte imbalances, immunological dysfunction and disorders of reproduction have been reported in animals and man. Vocal cord paralysis, pancreatitis, cardiac arrhythmias and a wide range of neuropsychiatric disorders are known to follow acute and chronic exposure to organophosphorus compounds. As a result of the inhibition of plasma cholinesterase, there can be increased sensitivity to drugs hydrolysed by this enzyme, e.g. suxamethonium and mivacurium. The inhibition of acetylcholinesterase causes dysfunction at the neuromuscular junction which can produce altered responses to nondepolarizing neuromuscular blockers. Anaesthetists may encounter patients exposed to organophosphorus compounds either following acute poisoning, trauma (warfare) or as patients with a wide range of nonspecific disorders presenting for surgery. The traditional use of oximes and atropine in treatment has failed to reduce the morbidity and mortality associated with poisoning. The roles of agents that have reduced the toxicity of organophosphorus compounds in animal experiments are discussed as potential therapeutic agents. There is an urgent need for accurate information on the problems associated with exposure to organophosphorus compounds. This would best be achieved by collaborative research between technologically advanced countries and developing countries, where organophosphorus compounds are a leading cause of ill health.

The establishment of cause–effect relationships is fundamental for the interpretation and the predictive value of biomarker responses measured at all levels of biological complexity. In the present study, the biochemical exposure biomarker acetylcholin-esterase (AChE) inhibition was related to locomotor behavior, representing a general effect biomarker at the organismal level. Both sexes of the carabid beetle Pterostichus cupreus were intoxicated with three doses of the organophosphorous insecticide dimethoate. Five elements of their locomotor behavior were measured for 4 h employing computer-aided video tracking, whereupon the whole body AChE activity was measured in the individual beetle. AChE inhibition was strongly correlated with dimethoate dose in both sexes. Alterations in the locomotor behavior were directly correlated with AChE inhibition in male beetles, which responded by reducing the time in locomotion, average velocity, and path length and by increasing the turning rate and frequency of stops. Females responded similarly at the two highest doses, whereas their locomotor behavior was not significantly different from the control group at the lowest dimethoate dose, suggesting a sex-dependent difference in behavioral sensitivity to minor AChE depressions. The results demonstrate that automated measurements of locomotor behavior is at least as sensitive an endpoint to organophosphate poisoning as the AChE assay. Further, the correlation between the molecular and behavioral responses in individual beetles indicates a mechanistic relationship between the two biomarkers.

Nine patients with organophosphorus (OP) intoxication developing neuromuscular transmission defects were given pancuronium 1, 2, or 4 mg intravenously (IV). Thirteen patient controls with hypoxic encephalopathy received similar dosages. The responses were monitored electrophysiologically using single and repetitive nerve stimulation (20 and 50 Hz). In OP patients, pancuronium did not alter the amplitude of the single CMAP, whereas its repetitive discharges were reduced. Severe neuromuscular blocks were reversed only partially by pancuronium 4 mg. In less severe blocks, 1 and 2 mg resulted in marked improvement. In the patient controls, pancuronium 4 mg induced a severe neuromuscular block but not with 1 and 2 mg. Pancuronium dosages necessary to reverse severe OP-induced neuromuscular blockade produce a neuromuscular block when AChE activity is normal. Low dosages have little effect on normal neuromuscular transmission, but improve the block to a mild degree and may be useful as part of treatment in OP intoxications. 1995 John Wiley & Sons, Inc.

To evaluate chronic effects of acute organophosphate pesticide poisoning, quantitatively determined vibrotactile thresholds were measured as an index of peripheral neuropathy among agricultural workers in Nicaragua. Thirty-six male workers were evaluated between 10 and 34 months after hospitalization for acute organophosphate poisoning and compared to an age- and sex-matched community reference group. Vibrotactile thresholds were measured quantitatively in right and left index fingers and right and left great toes. Study subjects were stratified into three groups: 1) never poisoned; 2) poisoned with organophosphates other than methamidophos, agents which have not been reported to cause peripheral neuropathy; and 3) poisoned with methamidophos, a peripheral neurotoxin. For all digits, there was a statistically significant trend of increasing age- and height-adjusted thresholds across these three exposure categories. Over one fourth of patients previously poisoned with methamidophos we studied had abnormal vibrotactile thresholds. These results suggest that previously reported cases of organophosphate-induced delayed polyneuropathy may represent only the worst disease in a spectrum of impairment, a sequela of exposure that may be much more common than previously thought.

A 9-year-old child presented with documented organophosphate insecticide poisoning. His course was initially complicated by a tachyarrhythmia with QT-interval prolongation that responded promptly to intravenous magnesium. However, following partial recovery, he developed progressive acute respiratory distress syndrome characterized by irreversible fibrosis and obliteration of the lung parenchyma. J Paediatr Child Health

Organophosphates (OP) are irreversibly bound to cholinesterase, causing deactivation of acetylcholinesterase. As a result of inhibition of plasma cholinesterase, increased sensitivity to drugs hydrolyzed by this enzyme can occur, e.g. succinylcholine and mivacurium. A case of more prolonged succinylcholine-induced paralysis in a child with undiagnosed acute OP insecticide poisoning is presented. A 7-h period of apnea and paralysis after administration of succinylcholine was attributed to the decreased rate of succinylcholine metabolism resulting from inhibition of pseudocholinesterase by the insecticide. In seven previously reported cases of prolonged succinycholine apnea after OP poisoning, exposure to insecticide was in chronic or subacute form without any obvious symptoms, and the duration of apnea did not extend up to 4 h, whereas in our case with acute, severe poisoning, succinylcholine led to more prolonged muscle paralysis. In the anesthetic management of patients with acute OP poisoning, succinylcholine should be avoided.

To the Editor, Acutepoisoningisoneofthecommonreasonsforhospitalisation in developing countries. 1 In countries like India, where the economy is linked substantially to agriculture, thenumberofcasesofacutepoisoningincreaseeveryyear. While in developed countries, the rate of mortality from poisoning ranges from 1% to 2% in developing countries like India, it varies between 15% and 30% and is the fourth mostcommoncauseofmortality,especiallyinruralIndia. 2 The rapid increase in the use of newer chemicals with potentiallyharmfuleffectsisamatterofconcerntothephysician and makes the management more challenging. 3 The monsoon-dependent agricultural practice and socioeconomic factors related to it also play a role in the incidence of acute poisonings. 4 Insufficient regulation for the sale and use of pesticides, lack of surveillance systems, insufficient enforcement regarding safe use of pesticides, lack of training of healthcare professionals regarding the managementaspects,inadequateaccesstoinformationsystem,and poorly maintained or non-existent personal protective equipmentarethemajorfactorsresponsibleforhigherincidence rate of poisoning. 5 Early diagnosis, treatment and prevention are crucial in reducing the burden of poisoning-related injury in any country. 6 A thorough knowledge about the nature andmagnitude of the problem in a particular area is essential for the doctors in hospital practice. In Indiathe exactincidenceofacutepoisoningcannot be defined properly due to under-reporting of cases to Government authorities. India has an over-usage of pesticides, and in particular organophosphate poisoning is most commonly reported in the emergency departments of Indian hospitals. 7 The data from poison information centre of All India Institute of Medical Sciences (AIIMS) reveals that highest incidence of poisoning cases was found in the age group of 14–40 years, with a preponderance of males affected. 8 According to the World Health Organization (WHO), 99% of the fatal poisoning cases occur in developing countries, predominantly among farmers. 4, 9, 10