Seizures high-dose exposure

Generally, according to high-dose exposure studies, animals exposed to nerve agents that exhibit seizures that are not promptly controlled develop brain damage and subsequent neurobehavioral problems. Animals that do not develop seizures or those that are rapidly and effectively treated with drugs that stop the seizures suffer no brain lesion and display no long-term neurobehavioral deficits. 

A short-term high-dose exposure could result in a brain disorder escalating to seizures, coma or even death. Long-term low-level exposure can decrease reaction time, cause nervous system damage, kidney disease, reproductive impairment, or death. 

Inhalation of small amounts of mustard gas produees nasal diseharge, sneezing, epistaxis, and coughing within 12 to 24 h of exposure. Higher concentrations or longer exposures can cause pulmonary damage, hypoxia, and respiratory acidosis. Seizures may be seen with extremely acute, high doses (Sidell et al, 1997). 

FIGURE 63.2. Experimental design for demonstration of how insufficient prophylactic treatment can be compensated for by adjunct post-exposure treatment. Low dose of scopolamine requires additional treatment (A). High dose of scopolamine is sufficient to terminate seizures (B). High dose of scopolamine given outside the cholinergic window requires additional treatment (C). 

Four of eight children developed acute neurological toxicity. Three had seizures and one had transient blindness after high-dose cisplatin (200 mg/m ) given by continuous infusion over 5 days, followed 10 days later by a further 2 days with 40 mg/m /day. These children had the greatest deterioration in renal function, and they may have had impaired clearance of and increased exposure to cisplatin (84). 

In addition to the hazards associated with meth production, it is becoming increasingly clear that heavy meth users risk a number of health problems. Exposure to very high doses poses a risk of seizures, convulsions, and cardiovascular collapse. Overdose can also produce the paranoid symptoms of stimulant psychosis often associated with violent behavior. A recent study of young adults who were heavy meth users found that over one third of the respondents reported committing acts of violence while under the influence of meth (Sommers, Baskin, Baskin-Sommers, 2006). Chronic users face additional problems. Depression is a common feature of methamphetamine withdrawal... 

The literature on the toxicity of benzene in humans is extensive. The acute effects of benzene exposure generally differ markedly from the chronic effects. Acute exposure to high doses of benzene in air (at concentrations in excess of 3000 ppm) causes symptoms typical of organic solvent intoxication. Symptoms may progress from excitation, euphoria, headache, and vertigo, in mild cases, to central nervous system depression, confusion, seizures, coma, and death from respiratory failure in severe cases. The rate of recovery depends on the initial exposure time and concentration, but, following severe intoxication, the symptoms may persist for weeks. 

Chronic exposure to high doses of T4 may cause thyrotoxicosis. The development of thyrotoxicosis in an acute exposure is rare. Thyrotoxicosis is characterized by tachycardia, cardiac arrhythmias, hypertension, hyperpyrexia, tremors, and seizures. In patients with severe toxicity, coma and circulatory collapse can result. 

Primary effects of methyl bromide are on the nervous system, lungs, nasal mucosa, kidneys, eyes, and skin. Neurologic symptoms include blurred vision, mental confusion, paresthesias, tremors, and speech defects. Severe exposure may result in narcosis, seizures, coma followed by respiratory paralysis, and circulatory failure. Contact with the skin and eyes can lead to irritation and burns. After an acute single, small with prompt recovery, no delayed or long-term effects are likely to occur. In larger exposures inhalation can cause injury to the nervous system, lungs, and throat. High doses can also injure the kidneys and liver. 

Animal studies show the olfactory and limbic pathways are particularly susceptible to kindling, the ability of a stimulus previously unable to induce a seizure to later induce one. Animal studies also show that acute administration of a high dose or intermittent repeated low-dose exposures to chemicals cause limbic kindling , and that this response is amplified depending on the time between stimuli. Kindling without a seizure has been shown to cause affective behavior changes in animals. Kindling could amplify reactivity and lower the threshold response to low levels of chemicals. 

One of the extremely toxic organophos-phorus pesticides cholinesterase inhibitor exhibits acute, delayed, and chronic effects toxic symptoms include headache, dizziness, muscle spasms, pinpoint pupils, blurred vision, weakness, abdominal pain, vomiting, nausea, diarrhea, and seizure high exposure may cause coma and death other symptoms are chest pain, low or high blood pressure, shortness of breath, psychosis, respiratory depression, and respiratory paralysis readily absorbed through skin effects may be delayed by several hours ingestion can cause immediate seizure or loss of consciousness probable oral lethal dose within the range... 

---