- Published on
Toxicology – Organophosphate Poisoning
Sources
Organophosphates are found in both chemical warfare agents—such as sarin, soman, tabun, and VX—and commonly used agricultural insecticides including diazinon, dichlorvos, malathion, and parathion.
Typical Presentation
A classic case involves accidental ingestion or exposure, often in agricultural settings. Patients may present with altered mental status, pinpoint pupils (miosis), excessive secretions, slow heart rate, bronchorrhea, sweating, and respiratory distress requiring airway support.
Mechanism of Action
Organophosphates inhibit acetylcholinesterase at synapses in both the central and peripheral nervous systems, as well as in red blood cells. This leads to accumulation of acetylcholine. Over time, the enzyme undergoes “aging,” making the inhibition irreversible.
Clinical Features
Muscarinic effects are most prominent and include miosis, bradycardia, excessive salivation, sweating, bronchorrhea, bronchospasm, gastrointestinal symptoms (nausea, vomiting, diarrhea), lacrimation, and urinary incontinence. Central nervous system effects include confusion, lethargy, coma, and seizures. Nicotinic effects include muscle fasciculations and weakness. Severe toxicity may be fatal.
Management
Treatment begins with decontamination and supportive care. Atropine is administered to counteract muscarinic effects, particularly respiratory secretions, starting at 2–5 mg IV in adults (0.05 mg/kg in children) and repeated every 3–5 minutes with dose escalation until improvement is seen. Pralidoxime is used to reverse neuromuscular effects and is given intravenously over 30 minutes (1–2 g in adults, 20–50 mg/kg in children). Benzodiazepines, especially diazepam, are used for seizures, agitation, and muscle spasms. Repeated dosing or continuous infusions may be necessary. Autoinjectors containing atropine and pralidoxime are commonly used in emergency and military settings.
Sources
Organophosphates are found in both chemical warfare agents—such as sarin, soman, tabun, and VX—and commonly used agricultural insecticides including diazinon, dichlorvos, malathion, and parathion.
Typical Presentation
A classic case involves accidental ingestion or exposure, often in agricultural settings. Patients may present with altered mental status, pinpoint pupils (miosis), excessive secretions, slow heart rate, bronchorrhea, sweating, and respiratory distress requiring airway support.
Mechanism of Action
Organophosphates inhibit acetylcholinesterase at synapses in both the central and peripheral nervous systems, as well as in red blood cells. This leads to accumulation of acetylcholine. Over time, the enzyme undergoes “aging,” making the inhibition irreversible.
Clinical Features
Muscarinic effects are most prominent and include miosis, bradycardia, excessive salivation, sweating, bronchorrhea, bronchospasm, gastrointestinal symptoms (nausea, vomiting, diarrhea), lacrimation, and urinary incontinence. Central nervous system effects include confusion, lethargy, coma, and seizures. Nicotinic effects include muscle fasciculations and weakness. Severe toxicity may be fatal.
Management
Treatment begins with decontamination and supportive care. Atropine is administered to counteract muscarinic effects, particularly respiratory secretions, starting at 2–5 mg IV in adults (0.05 mg/kg in children) and repeated every 3–5 minutes with dose escalation until improvement is seen. Pralidoxime is used to reverse neuromuscular effects and is given intravenously over 30 minutes (1–2 g in adults, 20–50 mg/kg in children). Benzodiazepines, especially diazepam, are used for seizures, agitation, and muscle spasms. Repeated dosing or continuous infusions may be necessary. Autoinjectors containing atropine and pralidoxime are commonly used in emergency and military settings.
0 Comments
