pyrethrins chặn các kênh natri ở màng tế bào thần kinh, gây phóng điện của tế bào thần kinh lặp đi lặp lại. Pyrethrins phổ biến nhất gây ra các phản ứng quá mẫn, trong đó bao gồm co thắt phế quản và phản vệ. | 350 SECTION 1 3 TOXICOLOGY PYRETHRINS Pyrethrins block the sodium channel at the neuronal cell membrane causing repetitive neuronal discharges. Pyrethrins most commonly cause hypersensitivity responses which include bronchospasm and anaphylaxis. They may produce dermal pulmonary gastrointestinal GI and neurologic findings. HERBICIDES Toxicity of herbicides which are pesticides used to kill weeds leads to a wide variety of symptoms generally based upon which organ system has been exposed. Chlorphenoxy compounds may cause tachycardia dysrhythmias and hypotension and muscle toxicity manifested by muscle pain fasciculations and rhabdomyolysis. Common bipyridial herbicides are paraquat and diquat. Paraquat is especially toxic with caustic effects resulting in severe dermal corneal and mucous membrane burns including the respiratory and GI epithelium. Cardiovascular collapse may occur early especially in the case of large ingestions and results in pulmonary edema renal failure hepatic necrosis and multisystem organ failure. Metabolic acidosis is due to hypoxemia and multisystem organ failure. Urea-substituted compounds are much less toxic than other herbicides and generally cause few systemic effects other than methemoglobinemia. RODENTICIDES Sodium monofluoroacetate a commercial exterminator compound is converted to a metabolite fluorocitrate which interferes with the Krebs cycle. Signs and symptoms of toxicity include nausea lactic acidosis respiratory depression cardiovascular collapse and altered mental status. Strychnine toxicity results from its competitive antagonism of the inhibitory neurotransmitter glycine at the postsynaptic spinal cord motor neuron. Signs and symptoms of strychnine toxicity include facial grimacing muscle twitching severe extensor spasms and opisthotonos it eventually may lead to medullary paralysis and death. Thallium sulfate is absorbed through the skin by inhalation and through the GI tract. Exposure to thallium sulfate initially causes GI
