Classes of Toxic Agents
Agents by class, toxicity by mechanism
Drugs: acetaminophen via NAPQI; NSAIDs through prostaglandin inhibition with GI and renal effects; opioids cause respiratory depression; chemotherapy includes anthracycline cardiotoxicity and cisplatin nephrotoxicity and ototoxicity. Industrial chemicals: solvents depress the CNS and injure liver; benzene damages marrow; PCBs and dioxin act through the aryl hydrocarbon receptor; formaldehyde causes irritation and is carcinogenic. Pesticides: organophosphates and carbamates inhibit acetylcholinesterase, producing cholinergic excess (SLUDGE/DUMBELS); organophosphates age and respond to oximes, carbamates generally do not; pyrethroids alter sodium channels; organochlorines are persistent neurotoxicants; herbicides such as paraquat and glyphosate differ markedly. Metals: lead inhibits heme synthesis and harms neurodevelopment; mercury forms differ (methylmercury is neurotoxic, elemental vapor is pulmonary and CNS, inorganic salts are renal); cadmium targets the proximal tubule; arsenic causes skin lesions, vascular disease, and cancer. Natural toxins: aflatoxin B1 is a hepatic carcinogen, botulinum causes flaccid paralysis, tetrodotoxin blocks sodium channels, ricin inhibits ribosomes, amatoxin inhibits RNA polymerase. Biologicals include endotoxin and venoms.
Traps: do not lump cholinesterase inhibitors together, because reversibility and oxime benefit differ. Metal speciation determines target organ. Aflatoxin is a hepatic carcinogen, not a neurotoxin.
Rule of thumb: in organophosphate poisoning, give atropine for muscarinic effects and add pralidoxime early, before enzyme aging.