Toxic Substances and Poisons: Symptoms, First Aid and Antidotes

Toxic substances and poisons are chemical, biological, or physical agents that cause physiological harm, organ failure, or death upon entering the body. Exposure occurs through ingestion, inhalation, dermal absorption, or injection. Prompt recognition of toxidromes, delivery of stabilizing first aid, and administration of specific antidotes are critical for reversing toxicity and preventing fatal metabolic disruptions.

Classification of Toxic Agents

Poisons are classified according to their origin, chemical nature, and physiological targets in the human body.

Major Categories of Poisons

• Corrosive Poisons: Strong acids like sulfuric acid and nitric acid, and strong alkalis like sodium hydroxide and potassium hydroxide cause chemical burns and liquefactive or coagulative necrosis.
• Neurotoxins: Organophosphates, carbamates, strychnine, and snake venoms impair nerve signal transmission across central and peripheral nervous systems.
• Cellular and Metabolic Toxins: Cyanide, carbon monoxide, and hydrogen sulfide disrupt cellular respiration and mitochondrial ATP production.
• Heavy Metals: Lead, mercury, arsenic, and cadmium accumulate in soft tissues and bones, binding to essential sulfhydryl enzyme groups.
• Plant and Biological Toxins: Dhatura (Datura stramonium), aconite, ricin from castor seeds, and botulinum toxin from Clostridium botulinum cause systemic organ failure.

Classical Toxidromes and Characteristic Symptoms

A toxidrome is a constellation of clinical signs and symptoms associated with a specific class of poison.

Emergency First Aid and General Management

Standard initial care focuses on stabilizing vital functions and reducing toxin absorption before targeted therapy begins.

General First Aid Principles

• Inhaled Poisons: Remove the victim to fresh air immediately, loosen tight clothing around the neck, and administer supplemental oxygen.
• Dermal and Ocular Exposure: Flush the affected skin or eyes with running water for 15 to 20 minutes and discard contaminated clothing.
• Ingested Non-Corrosive Toxins: Activated charcoal binds poisons inside the gastrointestinal tract if given within one to two hours of ingestion.
• Corrosive Ingestions: Never induce vomiting or administer neutralizing acids or alkalis, as this causes secondary esophageal rupture and exothermic thermal injury.
• Snake Envenomation: Immobilize the affected limb with a splint at or below heart level; do not apply tight tourniquets or attempt wound suction.

Specific Antidotes and Their Mechanisms of Action

Antidotes neutralize poisons through competitive receptor antagonism, chemical chelation, metabolic redirection, or enzymatic reactivation.

Important Facts

• Activated charcoal is ineffective for ingestions of simple alcohols, strong acids, alkalis, lithium, and elemental iron.
• Potassium permanganate is used in gastric lavage as an oxidizing agent to neutralize alkaloids such as morphine, strychnine, and nicotine.
• Carbon monoxide binds to human hemoglobin with an affinity 200 to 250 times greater than that of oxygen, forming carboxyhemoglobin and causing cherry-red skin discoloration.
• A single castor bean contains enough ricin, a ribosome-inactivating protein, to cause fatal systemic cellular arrest.
• Botulinum toxin, produced by the anaerobic bacterium Clostridium botulinum, is the most lethal biological toxin known, with an estimated human lethal dose of less than one nanogram per kilogram.
• Cyanide inhibits cytochrome c oxidase in complex IV of the mitochondrial electron transport chain, arresting aerobic cellular ATP synthesis.
• Dhatura poisoning presents with the diagnostic triad of delirium, dilated pupils, and dry hot skin, historically called “dry as a bone, red as a beet, blind as a bat, hot as a hare, mad as a hatter.”
• Universal Antidote is a classical formulation consisting of two parts activated charcoal, one part magnesium oxide, and one part tannic acid.
• Methyl alcohol toxicity produces formic acid via alcohol dehydrogenase and formaldehyde dehydrogenase, causing severe metabolic acidosis and optic nerve demyelination that leads to irreversible blindness.
• Minamata disease is caused by chronic methylmercury poisoning from consuming contaminated marine life, leading to sensory loss, ataxia, and severe congenital neurological defects.
• Itai-Itai disease is caused by mass environmental cadmium poisoning, which triggers severe osteomalacia, painful bone fractures, and renal tubular dysfunction.
• Blackfoot disease is a peripheral vascular gangrene disorder caused by chronic exposure to high concentrations of inorganic arsenic in drinking water.