Organophosphate-Induced Intermediate Syndrome

Human red blood cell acetylcholinesterase activity: a revisit after fifteen years

Human red blood cell acetylcholinesterase (RBC-AChE) activity is valuable for detecting potential exposure to cholinesterase inhibiting substances (CIS). A reliable population-based RBC-AChE activity reference range is critical for early and massive clinical and occupational toxicology screening. Previous published studies were often limited to small numbers of subjects, various testing methods, and crude statistical data analyses. We tested 4818 adult subjects with a well-established 17-minute modified Michel method over a 2-year period. We conducted a retrospective data analysis and systematically investigated on the influences to testing values from gender, age, age group, and their combinations and interactions. No significant difference was observed in the testing values between males (mean, medium, interquartile range = 0.76, 0.76, 0.71-0.80 ΔpH/h, respectively) and females (mean, medium, interquartile range = 0.76, 0.76, 0.71-0.81 ΔpH/hour, respectively), when gender was the only factor considered (p = 0.7238). However, with age progression, male testing values exhibited a consistent upward trend, while females did not show any clear patterns. Linear regression analysis of the data revealed that gender, age, and age group more or less affected testing values either as independent variables or with their combinations and interactions. However, more potential factors need to be included to achieve better testing value predictions. We recommend the toxicological testing community to adopt a new set of age group specific RBC-AChE activity reference ranges for males (0.68-0.80, 0.69-0.81, 0.70-0.83, 0.71-0.84, and 0.73-0.87 ΔpH/h for 18-29, 30-39, 40-49, 50-59, and ≥60 years old, respectively) while keeping the current reference range (0.63-0.89 ΔpH/hour) for females.

Organophosphate Poisoning: Review of Prognosis and Management

The high annual mortality rate of organophosphorus (OP) poisoning indicates that the treatment is mostly ineffective in this regard. It has been suggested to add calcium channel blocking (CCB) drugs or magnesium sulfate (MgSO4) to normal care to decrease the release of acetylcholine (ACh) at the cholinergic synapse. Moreover, the diagnosis of OP poisoning is chiefly based on clinical evidence. Oximes and atropine are the recognized antidotes of OP. However, low-priced medications such as MgSO4 and sodium bicarbonate (NaHCO3), as well as novel adjunct therapies, have been introduced recently. Furthermore, antioxidants are recommended for managing OP poisoning. In addition, hemoperfusion, fresh frozen plasma (FFP), and K-oximes are a number of innovative management modalities that deserve further evaluation. However, prevention seems to be the most effective management modality in this respect. Therefore, this study aimed to briefly discuss the controversies in OP poisoning management and present recent advances in its management and prognosis. The results of this study revealed that multiple factors including type of exposure, acetylcholinesterase (AChE) plasma level, time of hospitalization, and severity confirming OP poisoning should be considered to provide the best treatment strategy.

Changes in motor behavior and lumbar motoneuron morphology following repeated chlorpyrifos exposure in rats

Chlorpyrifos is an organophosphate pesticide associated with numerous health effects including motor performance decrements. While many studies have focused on the health effects following acute chlorpyrifos poisonings, almost no studies have examined the effects on motoneurons following occupational-like exposures. The main objective of this study was to examine the broad effects of repeated occupational-like chlorpyrifos exposures on spinal motoneuron soma size relative to motor activity. To execute our objective, adult rats were exposed to chlorpyrifos via oral gavage once a day, five days a week for two weeks. Chlorpyrifos exposure effects were assessed either three days or two months following the last exposure. Three days following the last repeated chlorpyrifos exposure, there were transient effects in open-field motor activity and plasma cholinesterase activity levels. Two months following the chlorpyrifos exposures, there were delayed effects in sensorimotor gating, pro-inflammatory cytokines and spinal lumbar motoneuron soma morphology. Overall, these results offer support that subacute repeated occupational-like chlorpyrifos exposures have both short-term and longer-term effects in motor activity, inflammation, and central nervous system mechanisms.

Methamidophos poisoning: A paediatric case report

Methamidophos is a highly hazardous organophosphate and is known to cause an acute cholinergic toxidrome. Methamidophos use is not allowed in South Africa and therefore local data pertaining to methamidophos poisoning is very limited, with no paediatric clinical cases described. Methamidophos is an active metabolite of acephate, a commonly used organophosphate, registered for agricultural use in South Africa. We present a paediatric case of methamidophos poisoning with prolonged clinical effects. The patient experienced a prolonged cholinergic toxidrome lasting 10 days, with a period of near-full recovery during this time. We discuss the biological plausibility of the detected methamidophos being a byproduct of acephate. In addition, we highlight the importance of closer monitoring of patients with organophosphate poisoning in areas where acephate is commonly used.

Serial repetitive nerve stimulation studies in organophosphorus poisoning indicate two distinct pathophysiological processes occur at the neuromuscular junction in the intermediate syndrome

INTRODUCTION

Intermediate syndrome is an important cause of respiratory failure following acute organophosphorus pesticide poisoning. The objective of this study was to examine the pathophysiology of this syndrome by analysis of sequential repetitive nerve stimulation studies in patients with acute organophosphorus pesticide poisoning.

METHODS

Thirty-four consenting symptomatic patients with acute organophosphorus pesticide poisoning with intermediate syndrome (n = 10) or a milder forme fruste intermediate syndrome (n = 24) were assessed prospectively with daily physical examination and repetitive nerve stimulation done on the right and left median and ulnar nerves. The compound muscle action potential at 1, 3, 10, 15, 20 and 30 Hertz was measured with a train of ten stimuli. The amplitudes of the resulting stimuli were normalized to the first stimulus (100 per cent) and plotted against time. The decrease in the area under the curve of all the second stimulus compound muscle action potentials in the first 0.3 seconds was measured as a means of quantifying the refractory block. The decrease in the area under the curve under the 10, 15, 20 and 30 Hertz compound muscle action potentials relative to this pooled second stimulus compound muscle action potentials-area under the curve indicated the extent of additional rate-dependent block (decreasing compound muscle action potential-area under the curve over the first 0.3 seconds after the first stimulus with increasing Hertz).

RESULTS

These new measurements strongly correlated with the severity of weakness. Refractory block was seen in most patients but was more severe in those with intermediate syndrome than those with forme fruste (partial) intermediate syndrome (median 55 per cent versus 16 per cent, P = 0.0001). Similar large differences were found for rate-dependent block (30 per cent versus 7 per cent, P = 0.001), which was uncommon in forme fruste intermediate syndrome but found in nine out of 10 patients with intermediate syndrome. Rate dependent block was generally only observed after 24 hours. The simplest strong predictor was total block at 30 Hertz repetitive nerve stimulation (89 per cent [interquartile range 73 to 94 per cent] versus 21 per cent [4 to 55 per cent]; P < 0.0001), which was very similar to total block calculated by summing other calculations.

DISCUSSION

These findings likely represent depolarization and desensitization block from prolonged excessive cholinergic stimulation but it is not clear if these are from pre- or post-synaptic pathology. An animal model of intermediate syndrome with repetitive nerve stimulation studies might enable a better pathophysiological understanding of the two types of block.

LIMITATIONS

The limited number of repetitive nerve stimulation studies performed were sufficient to demonstrate proof-of-concept, but further studies with more patients are needed to better define the correlates, clinical relevance and possible diagnostic/prognostic roles for the use of this technique.

CONCLUSION

There are two easily distinguishable pathophysiological abnormalities in the neuromuscular block in intermediate syndrome. While they often coincide, both may be observed in isolation. The total and rate-dependent block at 30 Hertz are strongly associated with more severe weakness.

Atypical organophosphate poisoning and a successful case of prolonged intubation in a low-resource newly developed intensive care unit in rural Zambia

Organophosphate poisoning is a common, under-reported cause of attempted and completed suicide worldwide. Following the resolution of the acute cholinergic syndrome, patients may develop respiratory muscle and proximal limb weakness, known as intermediate syndrome. A young man was brought to our rural hospital unconscious, in extremis, due to organophosphate pesticide poisoning. He developed atypical intermediate syndrome with global paralysis, persistent fasciculations and prolonged cholinergic symptoms, differing from the recognised presentation. He was intubated for fifteen days in our newly developed intensive care unit. Limited treatment options and the absence of blood gases, electrolyte testing, ECGs, invasive monitoring and imaging, in conjunction with regular disruptions to electricity and oxygen, and complications including seizures and pneumonia, all made this prolonged intubation an ambitious and challenging endeavour. We offer learning points for the acute physician and rural intensivist, and a summary of our reflections and hints for best care when adapting to a resource-limited setting.

Navigating the Neurological Abyss: A Comprehensive Review of Organophosphate Poisoning Complications

Organophosphate poisoning is a significant global health concern with implications for both occupational and environmental settings. This comprehensive review thoroughly explores the biochemical basis, clinical presentation, diagnostic methods, treatment strategies, and long-term effects of organophosphate exposure. The acute phase is characterized by cholinergic crisis, respiratory distress, and neurological manifestations, while delayed complications include the intermediate syndrome and organophosphate-induced delayed neuropathy. Diagnostic approaches involve clinical evaluation, cholinesterase-level assessments, and imaging studies. Treatment strategies encompass decontamination, antidotes such as atropine and pralidoxime, and supportive care. Long-term effects may include cognitive and neurological sequelae, necessitating rehabilitation approaches such as physical and occupational therapy. Prevention strategies include stringent occupational safety guidelines, sustainable agricultural practices, and public awareness initiatives. The implications for clinical practice underscore the importance of a multidisciplinary approach. At the same time, the call to action emphasizes the need for collaborative efforts in prevention and awareness to mitigate the impact of organophosphate poisoning on public health and the environment.

Ameliorative Potential of Ginger (Zingiber officinale) following Repeated Coexposure with Fluoride and Dimethoate in Blood and Brain of Wistar Rats

Coexposure to exogenous neurotoxins, such as fluoride (F−) and dimethoate (DM), is a serious public health concern. In the current study, Wistar rats were exposed to DM (1/10th LD50) and F− (4.5 ppm) in drinking water individually as well as in combination continuously for 28 days and the effectiveness of ginger and quercetin was assessed in combating the oxidative stress-mediated combined toxic effects on blood and brain. Significant (p<0.05) reductions were observed in the levels of total antioxidant status (TAS), glutathione peroxidase (GPx), blood glutathione (GSH), activities of catalase (CAT), total thiols (TTH), superoxide dismutase (SOD), aryl esterase (AE), and acetylcholinesterase (AChE) whereas significant elevations (p<0.05) in malondialdehyde (MDA) and advanced oxidation protein products (AOPP) were recorded in blood and brain of coexposed rats. Administration of ginger and quercetin significantly (p<0.05) ameliorated the combined F- and DM-induced hematotoxicity as well as neurotoxicity as indicated by the levels of markers of oxidative injury in brain and blood in coexposed rats, which showed significant (p<0.05) improvement. Moreover, pathological changes, such as neurodegeneration, perivascular edema, and gliosis, observed after combined F− and DM toxicity in the brain (cerebrum and cerebellum) were markedly reduced after ginger supplementation.

Intermediate Syndrome Presenting as Extrapyramidal Oromandibular Dystonia Due to Organophosphorus Inhalation: A Rare Case Report

A 35-year-old male patient, a farmer by occupation, presented with a complaint of deviation of the angle of the mouth towards the right side while speaking. A cerebrovascular event was suspected in this patient. He had a history of exposure to propane and cypermethrin while spraying insecticide in his field. He has a history of chronic exposure to these compounds. Intermediate syndrome (IMS) also known as type II syndrome was diagnosed in this patient with the help of neuroimaging. On evaluation, the patient was found to be having oromandibular dystonia, which is an extrapyramidal symptom of type II syndrome.

Suspected intermediate syndrome in a dog after organophosphate poisoning

OBJECTIVE

To discuss the clinical presentation and successful treatment of a suspected case of intermediate syndrome due to organophosphate (OP) poisoning in a dog.

CASE SUMMARY

Two dogs presented with acute cholinergic signs after ingesting an OP insecticide containing 50% acephate. Clinical signs consistent with acute cholinergic crisis resolved in both dogs within 24 hours postingestion. One dog developed an onset of neurological signs consistent with intermediate syndrome approximately 24 hours postingestion. This patient's clinical signs resolved with the use of pralidoxime chloride.

NEW OR UNIQUE INFORMATION PROVIDED

OP poisoning most commonly presents as an acute cholinergic crisis, with rare instances of animals developing intermediate syndrome. Few reports of successful treatment and recovery from intermediate syndrome exist in the veterinary literature, particularly with instances in which 2 dogs within the same exposure setting were treated for acute cholinergic signs and only 1 progressed to an intermediate syndrome. This report also highlights the importance of early intervention with pralidoxime chloride prior to the onset of aging.

Mechanisms of Organophosphate Toxicity and the Role of Acetylcholinesterase Inhibition

Organophosphorus compounds (OPs) have applications in agriculture (e.g., pesticides), industry (e.g., flame retardants), and chemical warfare (nerve agents). In high doses or chronic exposure, they can be toxic or lethal. The primary mechanism, common among all OPs, that initiates their toxic effects is the inhibition of acetylcholinesterase. In acute OP exposure, the subsequent surge of acetylcholine in cholinergic synapses causes a peripheral cholinergic crisis and status epilepticus (SE), either of which can lead to death. If death is averted without effective seizure control, long-term brain damage ensues. This review describes the mechanisms by which elevated acetylcholine can cause respiratory failure and trigger SE; the role of the amygdala in seizure initiation; the role of M1 muscarinic receptors in the early stages of SE; the neurotoxic pathways activated by SE (excitotoxicity/Ca++ overload/oxidative stress, neuroinflammation); and neurotoxic mechanisms linked to low-dose, chronic exposure (Ca++ dyshomeostasis/oxidative stress, inflammation), which do not depend on SE and do not necessarily involve acetylcholinesterase inhibition. The evidence so far indicates that brain damage from acute OP exposure is a direct result of SE, while the neurotoxic mechanisms activated by low-dose chronic exposure are independent of SE and may not be associated with acetylcholinesterase inhibition.

A Study of Organophosphorus Induced Delayed Myelopathy: Uncommon Sequelae of a Common Poisoning

INTRODUCTION

Organophosphorus (OP) compounds, with their lipophilicity, are responsible for a spectrum comprising of acute cholinergic symptoms, intermediate syndrome, as well as delayed neurological sequelae in the form of OP-induced delayed neuropathy and subsequently, myeloneuropathy with predominantly thoracic cord affection, manifested on partial recovery of the neuropathy. The pathogenesis of this myeloneuropathy in humans is still not well perceived.

AIM OF STUDY

To determine the onset and course of development of delayed myeloneuropathy in patients of OP poisoning.

MATERIALS AND METHODS

Twelve patients of OP ingestion presenting with delayed myeloneuropathy were evaluated with prior history, examination, MR imaging, nerve conduction and electromyography studies, and various evoked potentials to elicit the pattern of disease manifestation and progression.

RESULTS

Among the included patients, a majority had consumed chlorpyrifos and permethrin composition, a majority had undergone gastric lavage. Five (41.7%) had experienced acute worsening and 8 (66.7%) patients had developed intermediate syndrome. OPIDN had appeared after a median of 4 (1-8) weeks after the poisoning. All patients had lower limb hypertonia with wasting and distal more than proximal weakness with pure motor or sensorimotor involvement. MRI showed thoracic cord atrophy in 3 (25%) patients. Motor-evoked potential with reduced amplitude was noted in lower limbs on lumbar stimulation but absent on cortical stimulation.

CONCLUSION

Various animal models have shown similar patterns of neurotoxicity in OP poisoning with predominant thoracic cord pathology. Further research in humans may be undertaken to elicit the pathogenesis, thereby improving the treatment modality.

Intermediate Syndrome Due to Organophosphate Poisoning: A Case Report

Organophosphates, also known as phosphate esters, are a category of pesticide compounds that function by indirectly inhibiting the activity of an enzyme called acetylcholinesterase (AChE). AChE is responsible for breaking down acetylcholine (ACh) at the neuromuscular junction into acetic acid and choline. These compounds cause various clinical presentations upon acute toxicity, among which intermediate syndrome (IMS) exhibits an unpredictable course. This report describes the case of a farmer who ingested monocrotophos and ethanol in a suicide attempt, leading to a prolonged stay in the hospital and invasive ventilation, along with complications including ventilator-associated pneumonia. The patient received a total of 9000 mg of atropine over his 14-day hospitalization period.

Multiple neurological effects associated with exposure to organophosphorus pesticides in man

This article reviews available data regarding the possible association of organophosphorus (OP) pesticides with neurological disorders such as dementia, attention deficit hyperactivity disorder, neurodevelopment, autism, cognitive development, Parkinson's disease and chronic organophosphate-induced neuropsychiatric disorder. These effects mainly develop after repeated (chronic) human exposure to low doses of OP. In addition, three well defined neurotoxic effects in humans caused by single doses of OP compounds are discussed. Those effects are the cholinergic syndrome, the intermediate syndrome and organophosphate-induced delayed polyneuropathy. Usually, the poisoning can be avoided by an improved administrative control, limited access to OP pesticides, efficient measures of personal protection and education of OP pesticide applicators and medical staff.

Organophosphate Insecticide Toxicity in Neural Development, Cognition, Behaviour and Degeneration: Insights from Zebrafish

Organophosphate (OP) insecticides are used to eliminate agricultural threats posed by insects, through inhibition of the neurotransmitter acetylcholinesterase (AChE). These potent neurotoxins are extremely efficacious in insect elimination, and as such, are the preferred agricultural insecticides worldwide. Despite their efficacy, however, estimates indicate that only 0.1% of organophosphates reach their desired target. Moreover, multiple studies have shown that OP exposure in both humans and animals can lead to aberrations in embryonic development, defects in childhood neurocognition, and substantial contribution to neurodegenerative diseases such as Alzheimer's and Motor Neurone Disease. Here, we review the current state of knowledge pertaining to organophosphate exposure on both embryonic development and/or subsequent neurological consequences on behaviour, paying particular attention to data gleaned using an excellent animal model, the zebrafish (Danio rerio).

Prevalence, clinical manifestations, laboratory findings, treatment, and outcome of intermediate syndrome in anticholinesterase pesticide intoxication of dogs: A retrospective study

Organophosphates and carbamates are important anticholinesterase intoxicants of humans and dogs. Intermediate syndrome (IMS) typically occurs 7-96 h following a toxicity-associated acute cholinergic crisis (ACC), and manifests clinically as weakness of the proximal limb, respiratory, and neck flexor muscles. The aim of this study was to describe the prevalence, clinical findings, and outcome of IMS in dogs. The medical records of a veterinary teaching hospital were searched for dogs diagnosed with ACC, IMS, or both, between 2017 and 2021. Case files were retrospectively reviewed. Six historical IMS cases were additionally reviewed. Thirty-two dogs were diagnosed with anticholinesterase intoxication during the search period, of which 23 (72 %) were only diagnosed with ACC, seven (22 %) progressed from ACC to IMS, and two (6 %) were only diagnosed with IMS. Duration of hospitalisation was longer in the IMS group compared to the ACC only group (P = 0.005). When all dogs with IMS (n = 15, including the six historical cases) were considered, survival was 100 %, including four (27 %) that required positive pressure mechanical ventilation following respiratory failure. Serum butyrylcholine esterase activity, a marker of cholinesterase activity, was below reference interval when first measured in 14 (93 %) of dogs; however, was not a useful as a recovery marker. IMS should be suspected in dogs demonstrating respiratory, neck, and proximal limb muscle paresis or paralysis, especially following clinical signs consistent with ACC. Absence of clinical signs consistent with ACC or butyrylcholine esterase activity within the reference interval does not exclude IMS as a differential.

Intermediate Syndrome and Marchiafava-Bignami Syndrome: Double Trouble in Weaning Off

Intermediate syndrome affects 10-40% of those with severe organophosphorus poisoning, causing delayed weakness in the proximal parts of the body, neck flexors, and breathing muscles. We present the case of organophosphorus poisoning that advanced to intermediate syndrome and subsequently worsened, with imaging later revealing the Marchiafava-Bignami condition, which aggravated the intermediate syndrome.

Assessment of the Serum Glucose/Potassium GLU/K Ratio as a Predictor of Intermediate Syndrome Following Acute Anticholinesterase Exposure

BACKGROUND

The widespread use of anticholinesterase-containing pesticides accounts for the considerable morbidity and mortality in Egypt and worldwide.

AIM

Few studies have investigated the predictors of intermediate syndrome (IMS). Therefore, in this study, we assessed the adequacy of the serum glucose/potassium (GLU/K) ratio as an early reliable tool to predict IMS incidence following intoxication with acute anticholinesterase compounds.

METHODS

A prospective cross-sectional study was conducted among patients who presented to Tanta University Poison Control Center, Egypt, and were diagnosed with acute anticholinesterase intoxication between January and August, 2021. Patients were categorized based on the primary outcome into IMS (+) and IMS (-) groups.

RESULTS

Overall, 243 patients were included, among whom 44 (18.1%) had IMS as the complication. Younger individuals with age ranging between 18 and <25 years constituted the main exposed age category in both groups. Vomiting and abdominal colic were the most commonly noted complaints in the included patients (94.2% and 63.8% of patients, respectively). The delay, length of hospital stay, mean blood pressure, O₂ saturation, Glasgow Coma Scale score, random blood glucose level, K concentration, GLU/K ratio, and dose of atropine administered were significant IMS predictors on an individual basis, and the GLU/K ratio was the most significant IMS predictor. At a cutoff value of >41.07%, the GLU/K ratio could significantly predict IMS (areas under the curves = 0.971, p < 0.001) with 93% accuracy, 93.2% sensitivity, and 93% specificity.

CONCLUSION

Although the clear pathophysiology of IMS remains to be elucidated, our results provide insight into the significant contribution of neurological affection, apart from the well-known direct toxic effect on muscles. Moreover, we demonstrated a significant association between the development of IMS and severity of organophosphorus compounds' exposure. Physicians should be vigilant to detect IMS early upon admission using the GLU/K ratio, which is a useful early IMS predictor.

Organophosphate pesticides and new-onset diabetes mellitus: From molecular mechanisms to a possible therapeutic perspective

Organophosphate is a commonly used pesticide in the agricultural sector. The main action of organophosphate focuses on acetylcholinesterase inhibition, and it therefore contributes to acute cholinergic crisis, intermediate syndrome and delayed neurotoxicity. From sporadic case series to epidemiologic studies, organophosphate has been linked to hyperglycemia and the occurrence of new-onset diabetes mellitus. Organophosphate-mediated direct damage to pancreatic beta cells, insulin resistance related to systemic inflammation and excessive hepatic gluconeogenesis and polymorphisms of the enzyme governing organophosphate elimination are all possible contributors to the development of new-onset diabetes mellitus. To date, a preventive strategy for organophosphate-mediated new-onset diabetes mellitus is still lacking. However, lowering reactive oxygen species levels may be a practical method to reduce the risk of developing hyperglycemia.

Successful management of a kitten with chlorpyrifos and cypermethrin toxicosis with pralidoxime and atropine

CASE SUMMARY

Organophosphates and pyrethroids have been widely used as agricultural and domestic insecticides. This case report describes a 3-month-old free-roaming female kitten, weighing 930 g, that developed hypersalivation, hypothermia, dyspnoea due to increased bronchial secretion, bradycardia, miosis and neurological signs, including restlessness, ataxia, disorientation, apparent hallucination, muscle twitching and seizures within 6 h of accidental ingestion of an insecticide containing chlorpyrifos (500 g/l) and cypermethrin (50 g/l). The kitten was treated empirically with intramuscular atropine and dexamethasone, and rectal diazepam. The history of insecticide exposure was obtained after 6 h of treatment and intramuscular 2-pyridine aldoxime methochloride (pralidoxime [2-PAM]) and atropine therapy was started 2 h later. Recovery was complicated by suspected aspiration, but there were no sequelae from the insecticide exposure and by 7 days post-ingestion the kitten was normal and playful.

RELEVANCE AND NOVEL INFORMATION

To the best of our knowledge, this is the first report of successful management of chlorpyrifos and cypermethrin toxicosis in a cat in Bangladesh. This case report suggests that 2-PAM followed by atropine and other supportive therapy may be an effective strategy to manage a cat poisoned by chlorpyrifos and cypermethrin; however, expanded clinical trials are needed.

Outcomes of elderly patients with organophosphate intoxication

This study analysed the clinical patterns and outcomes of elderly patients with organophosphate intoxication. A total of 71 elderly patients with organophosphate poisoning were seen between 2008 and 2017. Patients were stratified into two subgroups: survivors (n = 57) or nonsurvivors (n = 14). Chlorpyrifos accounted for 33.8% of the cases, followed by methamidophos (12.7%) and mevinphos (11.3%). Mood, adjustment and psychotic disorder were noted in 39.4%, 33.8% and 2.8% of patients, respectively. All patients were treated with atropine and pralidoxime therapies. Acute cholinergic crisis developed in all cases (100.0%). The complications included respiratory failure (52.1%), aspiration pneumonia (50.7%), acute kidney injury (43.7%), severe consciousness disturbance (25.4%), shock (14.1%) and seizures (4.2%). Some patients also developed intermediate syndrome (15.5%) and delayed neuropathy (4.2%). The nonsurvivors suffered higher rates of hypotension (P < 0.001), shock (P < 0.001) and kidney injury (P = 0.001) than survivors did. Kaplan-Meier analysis indicated that patients with shock suffered lower cumulative survival than did patients without shock (log-rank test, P < 0.001). In a multivariate-Cox-regression model, shock was a significant predictor of mortality after intoxication (odds ratio 18.182, 95% confidence interval 2.045-166.667, P = 0.009). The mortality rate was 19.7%. Acute cholinergic crisis, intermediate syndrome, and delayed neuropathy developed in 100.0%, 15.5%, and 4.2% of patients, respectively.

Impaired neuromuscular function by conjoint actions of organophosphorus insecticide metabolites omethoate and cyclohexanol with implications for treatment of respiratory failure

BACKGROUND

Ingestion of agricultural organophosphorus insecticides is a significant cause of death in rural Asia. Patients often show acute respiratory failure and/or delayed, unexplained signs of neuromuscular paralysis, sometimes diagnosed as "Intermediate Syndrome". We tested the hypothesis that omethoate and cyclohexanol, circulating metabolites of one agricultural formulation, cause muscle weakness and paralysis.

METHODS

Acetylcholinesterase activity of insecticide components and metabolites was measured using purified enzyme from eel electroplaque or muscle homogenates. Mechanomyographic recording of pelvic limb responses to nerve stimulation was made in anaesthetized pigs and isometric force was recorded from isolated nerve-muscle preparations from mice. Omethoate and cyclohexanol were administered intravenously or added to physiological saline bathing isolated muscle. We also assessed the effect of MgSO₄ and cooling on neuromuscular function.

RESULTS

Omethoate caused tetanic fade in pig muscles and long-lasting contractions of the motor innervation zone in mouse muscle. Both effects were mitigated, either by i.v. administration of MgSO₄ in vivo or by adding 5 mM Mg²⁺ to the medium bathing isolated preparations. Combination of omethoate and cyclohexanol initially potentiated muscle contractions but then rapidly blocked them. Cyclohexanol alone caused fade and block of muscle contractions in pigs and in isolated preparations. Similar effects were observed ex vivo with cyclohexanone and xylene. Cyclohexanol-induced neuromuscular block was temperature-sensitive and rapidly reversible.

CONCLUSIONS

The data indicate a crucial role for organophosphorus and solvent metabolites in muscle weakness following ingestion of agricultural OP insecticide formulations. The metabolites omethoate and cyclohexanol acted conjointly to impair neuromuscular function but their effects were mitigated by elevating extracellular Mg²⁺ and decreasing core temperature, respectively. Clinical studies of MgSO₄ therapy and targeted temperature management in insecticide-poisoned patients are required to determine whether they may be effective adjuncts to treatment.

Factors associated with time to successful weaning in mechanically ventilated organophosphate poisoned patients

We designed this study to identify the factors associated with time to successful weaning in mechanically ventilated organophosphate (OP)-poisoned patients as the primary outcomes while duration of mechanical ventilation (MV) support, intensive care unit (ICU), and hospital length of stay (LOS) and in-hospital mortality as the secondary outcomes. We conducted a retrospective study of mechanically ventilated OP-poisoned patients admitted to the ICU of Poison Control Center of Ain Shams, Cairo, Egypt, starting from January 2019 to December 2019. Weaning was considered successful if the patient succeeded in the first spontaneous breathing trial of weaning and did not need reinstitution of MV. We used Cox proportional hazards regression models to identify factors associated with time to successful weaning in the studied patients. A total of 55 patients were enrolled in the study. Thirty-eight patients were weaned successfully. Lower initial red cell distribution width (RDW) levels [adjusted hazard ratio (HR), 0.299, 95% confidence interval (CI) (0.184-0.486)] and lower initial doses of atropine [adjusted HR, 0.97, 95% CI (0.935-0.999)] were independently associated with shorter time to achieve successful weaning. Successfully weaned patients had significantly longer hospital LOS (p = 0.019) and no reported in-hospital mortality (p < 0.001) compared with patients who failed to wean. We concluded that initial RDW and initial doses of atropine were found to be the strongest factors associated with time to successful weaning in mechanically ventilated OP-poisoned patients. RDW and atropine can be used as simple risk assessment tools in OP poisoning.

Assessment of the cytotoxic and mutagenic potential of dichlorvos (DDVP) using in silico classification model; a health hazard awareness in Nigeria

Dichlorvos (DDVP) has been abused in Nigeria for suicide attempts, topical applications to treat an ectoparasitic infestation, and indiscriminate use on farm produce. Exposure to this compound in subacute concentration can cause toxicity in different tissues by alteration of the cellular antioxidative defence mechanism. This analysis is aimed at the systematic profiling of DDVP to assess its cytotoxic and mutagenic potential for human vulnerability using an in silico classification model. DDVP was grouped into categories of analogue chemical compounds generated from inventories based on structural alerts that measure the biological effects on cell lines and animal models using the quantitative structure-activity relationship (QSAR) model. The cytotoxic and mutagenic potential of DDVP was assessed by analyzing target endpoints like skin sensitization, oral/inhalation toxicity, neurotoxicity and mutagenicity. DDVP shows moderate sensitization potential that can induce skin irritation during prolonged exposure because of the presence of dichlorovenyl side-chain that interacts with cellular proteins and causes degradation. 50% lethal dose (LD₅₀) of DDVP per body weight was determined to be 26.2 mg/kg in a rat model at 95% confidence range for acute oral toxicity, and 14.4 mmol/L was estimated as 50% lethal concentration (LC₅₀) in the atmosphere due to acute inhalation toxicity. DDVP can also inhibit acetylcholinesterase in the nervous system to produce nicotinic and muscarinic symptoms like nausea, vomiting, lacrimation, salivation, bradycardia, and respiratory failure may cause death. The widely used pesticide causes weak DNA methylation which can repress gene transcription on promoter sites. DDVP is volatile so it can cause oral and inhalation toxicity coupled with neurotoxicity during prolonged exposure. Serum cholinesterase blood tests should be encouraged in federal and state hospitals to investigate related health challenges as DDVP is still used in Nigeria.

Organophosphorus Nerve Agents: Types, Toxicity, and Treatments

Organophosphorus compounds are extensively used worldwide as pesticides which cause great hazards to human health. Nerve agents, a subcategory of the organophosphorus compounds, have been produced and used during wars, and they have also been used in terrorist activities. These compounds possess physiological threats by interacting and inhibiting acetylcholinesterase enzyme which leads to the cholinergic crisis. After a general introduction, this review elucidates the mechanisms underlying cholinergic and noncholinergic effects of organophosphorus compounds. The conceivable treatment strategies for organophosphate poisoning are different types of bioscavengers which include stoichiometric, catalytic, and pseudocatalytic. The current research on the promising treatments specifically the catalytic bioscavengers including several wild-type organophosphate hydrolases such as paraoxonase and phosphotriesterase, phosphotriesterase-like lactonase, methyl parathion hydrolase, organophosphate acid anhydrolase, diisopropyl fluorophosphatase, human triphosphate nucleotidohydrolase, and senescence marker protein has been widely discussed. Organophosphorus compounds are reported to be the nonphysiological substrate for many mammalian organophosphate hydrolysing enzymes; therefore, the efficiency of these enzymes toward these compounds is inadequate. Hence, studies have been conducted to create mutants with an enhanced rate of hydrolysis and high specificity. Several mutants have been created by applying directed molecular evolution and/or targeted mutagenesis, and catalytic efficiency has been characterized. Generally, organophosphorus compounds are chiral in nature. The development of mutant enzymes for providing superior stereoselective degradation of toxic organophosphorus compounds has also been widely accounted for in this review. Existing enzymes have shown limited efficiency; hence, more effective treatment strategies have also been critically analyzed.

Molecular Modeling Study of Uncharged Oximes Compared to HI-6 and 2-PAM Inside Human AChE Sarin and VX Conjugates

The deleterious effects of nerve agents over the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) turned these compounds into the most dangerous chemical weapons known. Among the antidotes in use today against these agents, oximes in combination with other drugs are the only treatment with any action. HI-6 and 2-PAM are cationic oximes proved to be effective for the reactivation of AChE inhibited by the nerve agents VX and sarin (GB). However, when it comes to reactivation of AChE inside the central or peripheral nervous systems, charged molecules present low diffusion due to low penetration through the blood-brain barrier. Uncharged oximes appear as an interesting alternative to solve this problem, but the development and enhancement of more efficient uncharged oximes capable of reactivating human AChE is still necessary. Given the limitations for in vivo and in vitro experimental studies with nerve agents, modeling is an important tool that can contribute to a better understanding of factors that may affect the efficiency of uncharged oximes. In order to investigate the interaction and behavior of cationic and uncharged oximes, we performed here molecular docking, molecular dynamics simulations, and binding energies calculations of the known cationic oximes HI-6 and 2-PAM plus four uncharged oximes found in the literature, complexed with human AChE (HssACHE) conjugated with the nerve agents VX and GB. The uncharged oximes showed different behaviors, especially RS194B, which presented stability inside AChE-VX, but presented free binding energy lower than cationic oximes, suggesting that structural alterations could favor its interactions with these complexes. In contrast, HI-6 and 2-PAM showed higher affinities with more negative binding energy values and larger contribution of the amino acid Asp74, demonstrating the importance of the quaternary nitrogen to the affinity and interaction of oximes with AChE-GB and AChE-VX conjugates.

Neurotoxicity of pesticides

Pesticides are unique environmental contaminants that are specifically introduced into the environment to control pests, often by killing them. Although pesticide application serves many important purposes, including protection against crop loss and against vector-borne diseases, there are significant concerns over the potential toxic effects of pesticides to non-target organisms, including humans. In many cases, the molecular target of a pesticide is shared by non-target species, leading to the potential for untoward effects. Here, we review the history of pesticide usage and the neurotoxicity of selected classes of pesticides, including insecticides, herbicides, and fungicides, to humans and experimental animals. Specific emphasis is given to linkages between exposure to pesticides and risk of neurological disease and dysfunction in humans coupled with mechanistic findings in humans and animal models. Finally, we discuss emerging techniques and strategies to improve translation from animal models to humans.

Potential attenuation of early-life overfeeding-induced metabolic dysfunction by chronic maternal acetylcholinesterase inhibitor exposure

Evidence suggests that low concentration perinatal exposure to environmental contaminants, such as organophosphate (OP) is associated with later life insulin resistance and type 2 diabetes. The aim of this work was to investigate whether chronic maternal OP exposure exacerbates metabolic dysfunctions in early-overfed rats. During pregnancy and lactational periods, dams received OP by gavage. To induce neonatal overnutrition at postnatal day 3, pups were standardized to 9 or 3 per nest. At 90-days-old, glucose-insulin homeostasis and insulin release from pancreatic islets were analyzed. While both OP exposure and overfeeding alone did induce diabetogenic phenotypes in adulthood, there was no exacerbation in rats that experienced both. Unexpectedly, the group that experienced both had improved adiposity, metabolic parameters, attenuated insulin release from isolated islets in the presence of glucose and low function of muscarinic acetylcholine receptor M3, as well as an attenuation of beta cell mass hyperplasia. High levels of butyrylcholinesterase and low levels of insulin in milk may contribute to the OP-induced developmental programming. Our study showed that maternal OP exposure may program insulin release as well as endocrine pancreas structure, thus affecting metabolism in adulthood. Our data suggest that while perinatal OP exposure alone increases the risk for later life T2D, it actually reverses many of the programmed metabolic dysfunction that is induced by postnatal overfeeding. These surprising results may suggest that low-dose administration of acetylcholinesterase inhibitors could be of utility in preventing detrimental developmental programming that is caused by early-life overnutrition.

Uso de pralidoxima en la intoxicación con metomilo en pastor collie en Medellín (Colombia). Reporte de caso

Se describe el uso de la pralidoxima en el tratamiento de una intoxicación con metomiloen un canino en la ciudad de Medellín (Colombia). Un macho de raza pastor colliesufrió intoxicación accidental con metomilo, presentó cuadro colinérgico, con miosis,sialorrea, delirio, excitación y emesis, fue sometido a descontaminación con carbónactivado y terapia con atropina (0,04 mg/kg IM) cada 30 minutos hasta atropinizar,difenhidramina (2 mg/kg EV) y pralidoxima (10 mg/kg EV) cada 8 horas y pentobarbital(12 mg/kg EV) por 24 horas, además de terapia de sostén. Se realizaron pruebashematológicas, creatinina, alanino aminotrasferasa, tiempo de protrombina y tiempoparcial tromboplastina que resultaron normales para la especie. Después de una terapiade 7 días el paciente presentó mejoría total de los signos nerviosos y se dio de alta encondición normal. El uso de pralidoxima como activador de la acetilcolinesterasa es unaopción en el tratamiento de la intoxicación grave por metomilo en la especie canina quemuestra sensibilidad a los carbamatos.

Novel Clinical Toxicology and Pharmacology of Organophosphorus Insecticide Self-Poisoning

Organophosphorus insecticide self-poisoning is a major global health problem, killing over 100,000 people annually. It is a complex multi-organ condition, involving the inhibition of cholinesterases, and perhaps other enzymes, and the effects of large doses of ingested solvents. Variability between organophosphorus insecticides—in lipophilicity, speed of activation, speed and potency of acetylcholinesterase inhibition, and in the chemical groups attached to the phosphorus—results in variable speed of poisoning onset, severity, clinical toxidrome, and case fatality. Current treatment is modestly effective, aiming only to reactivate acetylcholinesterase and counter the effects of excess acetylcholine at muscarinic receptors. Rapid titration of atropine during resuscitation is lifesaving and can be performed in the absence of oxygen. The role of oximes in therapy remains unclear. Novel antidotes have been tested in small trials, but the great variability in poisoning makes interpretation of such trials difficult. More effort is required to test treatments in adequately powered studies.

New insights into the organophosphate-induced intermediate syndrome

Acute organophosphate (OP) poisoning can be deadlier than any other type of chemical poisoning. So far, only a few cases have been described that include extensive neurological complications. We present an outstanding case of severe oral OP poisoning with intermediate syndrome developed on the fourth day after hospital admission. The clinical picture involved weakness of the proximal upper and lower limb muscles and several muscles supplied by motor cranial nerves, but, what is peculiar, the distal upper and lower limb muscles were also affected (forearms, hands, legs, and feet). To our knowledge, this is a unique presentation, as lower limb muscle weakness was reported only in the context of delayed polyneuropathy. Another remarkable feature was the involvement of six of the twelve cranial nerves, which makes this case of intermediate syndrome the first with such a spread of muscle weakness and provides new insights into the polymorphic clinical manifestations of acute OP poisoning.

Nephrotoxicity issues of organophosphates

Organophosphates are a large class of chemicals, initially invented in 1850 and since then they have been applied in numerous aspects of science to serve our purposes. Their mechanism of action in living organisms involves the irreversible inhibition of acetylcholinesterase, therefore they interfere with neuromuscular signal transmission. Due to the systematic and exaggerated use of these chemicals, there is massive exposure to them, hence there is great concern regarding the ramifications to all mammalian organisms. It has been widely accepted that over-exposure to organophosphates, has a deleterious impact on the renal tissue and subsequently on the renal function. Despite the significance of this global issue, limited knowledge exists, regarding the effect of these substances on our health. Therefore, new and extensive research is required to expand our knowledge and ensure proper guidance regarding the use of organophosphates as well the protection against their detrimental consequences. The aim of this review is to negotiate the effect of organophosphate exposure on renal tissue and kidney function.

Relationship between alcohol co-ingestion and outcome in profenofos self-poisoning - A prospective case series

INTRODUCTION

The importance of alcohol co-ingestion for outcome in organophosphorus (OP) insecticide self-poisoning has only been studied for the relatively hydrophilic dimethyl insecticide, dimethoate. We aimed to assess the effect of alcohol in acute poisoning with the lipophilic S-alkyl OP insecticide, profenofos.

METHODOLOGY

Demographic and clinical data, including an alcohol history, were prospectively collected from all cases of acute poisoning with agricultural profenofos EC50 presenting to two Sri Lankan hospitals over seven years.

RESULTS

Of 1859 patients with acute OP insecticide self-poisoning, 243 (13.1%) reported ingestion of profenofos (male 182/243, 74.9%). Alcohol co-ingestion was reported by 64/243 (26.3%). All patients reporting alcohol co-ingestion were male (64/64 [100%] vs 118/179 [65.9%] not reporting alcohol ingestion, p<0.001). More patients reporting alcohol co-ingestion died (10/64 [15.6%] vs 10/179 [5.6%]; p = 0.013) and required intubation (13/64 [20.3%] vs 16/179 [8.9%], p = 0.016) compared to those who did not co-ingest alcohol. Using multi-logistic regression, controlling for the estimated dose ingested, age (OR 11.1 [2.5 to 48.9] for age > 35 years vs ≤35 years) and alcohol co-ingestion (OR 3.1 [1.2 to 7.9]) were independently associated with increased risk of death. Increased risk of intubation was independently associated with age (OR 3.2 [1.6 to 6.6] for age > 35 years vs ≤35 years) and alcohol co-ingestion (OR 3.2 [1.6 to 6.4]).

CONCLUSION

A history of alcohol co-ingestion, as well as older age, is independently associated with worse outcome in patients' self-poisoned with profenofos.

Can we predict intermediate syndrome? A review

INTRODUCTION

Ingestion of organophosphorus insecticides (OPI) is a common method of deliberate self harm in the developing world. Deaths mainly follow as a result of the respiratory failure associated with both cholinergic crisis and the intermediate syndrome. Even though death can be prevented by early mechanical ventilation of these patients, limited studies are available regarding the prediction of intermediate syndrome and subsequent respiratory failure.

OBJECTIVE

To systematically review articles that are published with regard to possible prediction of intermediate syndrome using clinical, biochemical and electrophysiological parameters.

METHODS

A systematic review on literature published in English language was done in the PubMed database without a date limitation. Two sets of search terms were used. The first set consisted of MeSH Terms "organophosphates", "organophosphate poisoning", "op poisoning" "organophosphate insecticide poisoning" and "organophosphorus". The second set included the MeSH Terms "Intermediate syndrome", "proximal muscle weakness", "cranial nerve palsies", "respiratory depression" and "neck muscle weakness". Articles containing at least one word from each set were reviewed.

RESULTS

At least one MeSH term from each set was incorporated in 179 articles. Of these, 69 were rejected as they were not related to organophosphate poisoning or intermediate syndrome.

PREDICTION OF IMS

Clinical prediction is mostly based on ICU scoring systems. Biochemical markers such as reduced levels of serum and erythrocyte acetylcholine esterase have been studied many times. Both clinical and biochemical markers show a modest relationship in predicting IMS. Single fibre electromyography show promising results as it directly assesses neuromuscular junction.

CONCLUSION

The intermediate syndrome which follows organophosphate poisoning still remains a significant problem with its high morbidity. Clinical and biochemical markers show modest results in predicting IMS. Neurophysiological markers such as single fibre EMG should be studied further as they measure activity of affected nicotinic receptors directly.

Acute Generalized Weakness

Weakness is a common complaint in the emergency department, and a most challenging one, because before the emergency physician can proceed with an evaluation, the complaint of weakness must be fully clarified to determine about what the patient is actually complaining. This article will focus on causes of acute generalized nontraumatic bilateral weakness. Evaluation begins with the history and physical examination, followed by diagnostic testing in some cases.

Pharmacotherapy to protect the neuromuscular junction after acute organophosphorus pesticide poisoning

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.

Self-regeneration of neuromuscular function following soman and VX poisoning in spinal cord-skeletal muscle cocultures

Aside from nerve agents, various highly toxic pesticides belong to the group of organophosphorus (OP) compounds, thereby causing a large number of intoxications every year. Unfortunately, there are still shortcomings in the current treatment for OP poisoning and research on novel therapeutic options is restricted in several aspects. In this study we investigated the suitability of organotypic cocultures for pharmacological in vitro studies involving OP compounds. These slice cultures are derived from murine spinal cord and muscle tissue forming functional neuromuscular synapses, which trigger spontaneous contractions of muscle fibers. Using video microscopy to quantify muscle activity, we assessed the viability of cocultures after exposure to soman and VX, and the associated loss and recovery of neuromuscular function. Antidotal treatment was not provided. The application of nerve agents led to an almost complete loss of muscle activity. However, cell cultures regained equivalent muscular function to the control situation three and seven days after intoxication. In summary, the tested in vitro system could be a promising tool for the investigation of long term effects and therapeutic options for OP poisoning.

Pesticide poisoning and neurobehavioral function among farm workers in Jiangsu, People's Republic of China

Pesticides remain an integral part of agricultural activities worldwide. Although there have been a number of studies over the last two decades concerning the adverse effects of pesticide poisoning and chronic long term exposures on neurobehavioral function, the impact of recent pesticide poisoning and long term pesticide exposure on neurobehavioral function in Chinese farm workers has not been reported. China is the largest user of pesticides worldwide and figures suggest 53,300-123,000 Chinese people are poisoned every year. A case control study was conducted to examine the impact of recent pesticide poisoning on neurobehavioral function and the relationship between years worked in agriculture and lower performance on neurobehavioral tests. A total of 121 farm workers who self-reported recent pesticide poisonings within the previous 12 months (case group) and 80 farm workers who reported no pesticide poisoning in the previous 12 months (control group) were recruited from three areas of Jiangsu Province, China. The World Health Organization (WHO) recommended neurobehavioral core test battery (NCTB) was used to assess neurobehavioral functioning among cases and controls. Student's t tests and two-way covariance analysis (ANCOVA) were used to test for significant differences in the neurobehavioral test results between the groups. Scores on the Profile of Mood States (POMS) in the recently poisoned group were significantly higher for anger-hostility, depression-dejection, tension-anxiety and lower for vigor-activity compared to controls (p < .05). Digit span, digit symbol, Benton visual retention and pursuit aiming scores were all significantly lower among the recently poisoned group compared to the controls (p < .05). Two-way ANCOVA indicated significantly lower performance in correct pursuit aiming and higher error pursuit aiming amongst the recently poisoned group and those who had worked for more than 30 years in agriculture (p < .05). These findings provide important preliminary epidemiological evidence regarding the association between occupational pesticide exposure and neurobehavioral functioning in Chinese farm workers.

Organophosphorus and carbamate insecticide poisoning

Both organophosphorus (OP) and carbamate insecticides inhibit acetylcholinesterase (AChE), which results in accumulation of acetylcholine (ACh) at autonomic and some central synapses and at autonomic postganglionic and neuromuscular junctions. As a consequence, ACh binds to, and stimulates, muscarinic and nicotinic receptors, thereby producing characteristic features. With OP insecticides (but not carbamates), "aging" may also occur by partial dealkylation of the serine group at the active site of AChE; recovery of AChE activity requires synthesis of new enzyme in the liver. Relapse after apparent resolution of cholinergic symptoms has been reported with OP insecticides and is termed the intermediate syndrome. This involves the onset of muscle paralysis affecting particularly upper-limb muscles, neck flexors, and cranial nerves some 24-96 hours after OP exposure and is often associated with the development of respiratory failure. OP-induced delayed neuropathy results from phosphorylation and subsequent aging of at least 70% of neuropathy target esterase. Cramping muscle pain in the lower limbs, distal numbness, and paresthesiae are followed by progressive weakness, depression of deep tendon reflexes in the lower limbs and, in severe cases, in the upper limbs. The therapeutic combination of oxime, atropine, and diazepam is well established experimentally in the treatment of OP pesticide poisoning. However, there has been controversy as to whether oximes improve morbidity and mortality in human poisoning. The explanation may be that the solvents in many formulations are primarily responsible for the high morbidity and mortality; oximes would not be expected to reduce toxicity in these circumstances. even if given in appropriate dose.

Potential health effects associated with dermal exposure to occupational chemicals

There are a large number of workers in the United States, spanning a variety of occupational industries and sectors, who are potentially exposed to chemicals that can be absorbed through the skin. Occupational skin exposures can result in numerous diseases that can adversely affect an individual's health and capacity to perform at work. In general, there are three types of chemical-skin interactions of concern: direct skin effects, immune-mediated skin effects, and systemic effects. While hundreds of chemicals (metals, epoxy and acrylic resins, rubber additives, and chemical intermediates) present in virtually every industry have been identified to cause direct and immune-mediated effects such as contact dermatitis or urticaria, less is known about the number and types of chemicals contributing to systemic effects. In an attempt to raise awareness, skin notation assignments communicate the potential for dermal absorption; however, there is a need for standardization among agencies to communicate an accurate description of occupational hazards. Studies have suggested that exposure to complex mixtures, excessive hand washing, use of hand sanitizers, high frequency of wet work, and environmental or other factors may enhance penetration and stimulate other biological responses altering the outcomes of dermal chemical exposure. Understanding the hazards of dermal exposure is essential for the proper implementation of protective measures to ensure worker safety and health.