Substance
Parathion and other organophosphates

Pathology
Acetylcholinesterase inhibition, resulting in excessive acetylcholine stimulation of muscarinic and nicotinic receptors.

Symptoms
Nausea, vomiting, diarrhea, abdominal pain, tremor, muscle fasciculations, excessive salivation and sweating, dehydration, bradycardia, weakness, shock, death usually caused by respiratory paralysis.

Emergency Measures
Maintain airway and clear secretions. Provide assistance with ventilation. Decontaminate exposed skin and remove soaked clothing. Decontaminate the GI tract. Use atropine and/or pralidoxime for anticholinergic crises. Give diazepam or related drugs for seizures, and standard antiarrhythmic protocols for ventricular rhythm disturbances.

Comments
Toxicity depends on the relative toxicity of the organophosphate and the quantity involved.