Antidota

Antidota are substances that counteract the effects of poisons. They may neutralize toxins, block their action at the site of effect, or support the body's detoxification and elimination processes. Most antidotes are toxin-specific, but some provide general supportive care in poisoning.

Antidotes act by several mechanisms. Direct antagonists bind to receptors and reverse toxin effects, such as naloxone for opioid overdose or flumazenil for benzodiazepines. Chemical antidotes form inactive complexes with toxins, as seen with chelating agents used for metals (deferoxamine for iron; dimercaprol and EDTA for arsenic, lead). Enzyme-based antidotes accelerate detoxification, for example N-acetylcysteine for acetaminophen toxicity or fomepizole to inhibit alcohol dehydrogenase in methanol and ethylene glycol poisoning. Immunotherapies such as antivenoms neutralize venoms. Some antidotes reverse specific anticoagulation, including vitamin K for warfarin and protamine sulfate for heparin. Pralidoxime reactivates acetylcholinesterase in organophosphate poisoning, and digoxin immune Fab binds digoxin.

Limitations and considerations: not all poisons have antidotes, and effectiveness depends on timing and accuracy of diagnosis. Antidotes can have their own risks and are typically administered under medical supervision as part of a broader treatment plan that includes decontamination and supportive care. The concept of antidotes has evolved with modern pharmacology to improve outcomes after poisoning.