Regional toxicology in India

Tropical and regional toxicology in the Indian subcontinent involves the recognition and management of plant-derived poisons, food adulterants, snake envenomation, scorpion envenomation, and selected zoological toxins. Regional plant-derived poisons, including deliriants like Datura, irritants like Abrus precatorius, and spinal stimulants like Strychnos nux-vomica, present unique clinical profiles and significant forensic implications in cases of homicide, robbery, or malingering. Furthermore, public health crises can also arise from adulterants like Argemone mexicana, which causes epidemic dropsy. Management of envenomation by India’s Big Four venomous snakes hinges on specialized bedside diagnostics like the 20-minute whole blood clotting test and the timely administration of polyvalent anti-snake venom. Scorpion envenomation, particularly by the Indian red scorpion, may cause autonomic storm, pulmonary edema, and myocardial dysfunction. Spanish fly poisoning is caused by cantharidin, a potent irritant that primarily affects the skin, gastrointestinal tract, and urinary tract.

Plant-derived poisons in India are classified based on their primary physiological effects, such as irritation, delirium, neurotoxicity, or cardiotoxicity.

Seed-derived irritants/toxic agents

Toxic plant seeds contain active principles that can cause local irritation, gastrointestinal toxicity, and/or systemic poisoning, depending on the plant and route of exposure.

Deliriants and somniferous poisons

These substances primarily affect the central nervous system, leading to altered states of consciousness.

Datura

• Context: known as railway poison or roadside poison, as it is used to stupefy travelers for robbery
• Active principles
  • Hyoscine/scopolamine
  • Hyoscyamine
  • Atropine
• Charachteristics
  • All parts are poisonous, especially the seeds
  • Fruit: single, large, spiny capsule; also called thorn apple
  • Seeds: dark brown, thick, rough, kidney-shaped, and odorless
• Clinical presentation: anticholinergic toxidrome, including dilated pupils, dryness of mouth, delirium (muttering delirium), and drowsiness
• Antidote: physostigmine

Cannabis

• See "Cannabis-induced disorders."

Papaver somniferum (opium)

• See "Opioids" and "Opioid toxidrome."

Spinal and cardiac poisons

Strychnos nux-vomica and gelsemium are considered spinal poisons. They primarily affect spinal cord excitability, whereas digitalis, oleander, nicotine, and aconite are considered cardiac poisons due to their serious cardiotoxicity.

Strychnos nux-vomica

• Context: also known as kuchila or dog button
• Active principles
  • Strychnine: most potent toxin
  • Brucine
  • Loganin
• Toxicity: seeds are highly poisonous
• Postmortem features
  • Early rigor mortis
  • Postmortem caloricity
  • Delayed putrefaction
• See "Rodenticides" in "Poisoning" for information on pathophysiology and clinical features.

Aconite

• Context: also known as devil’s helmet, blue rocket, monkshood, wolfsbane
• Active principle: aconitine, mesaconitine, hypaconitine
• Toxicity: All parts are toxic.
• Clinical features: vomiting, diarrhea, perioral paraesthesia, cardiac arrhythmias, hippus, hypotension/shock

Oleanders

Cerbera odollam

• Context
  • Also known as dabur, dhakur, or the suicide tree
  • Fruit resembles a green mango
  • Kernel is most poisonous part
• Active principles
  • Cerberin
  • Odollotoxin
  • Cerberoside
  • Odollin
• Mechanism of action: cardiac glycoside toxicity with digitalis-like Na⁺/K⁺-ATPase inhibition
• Clinical features: nausea, vomiting, thrombocytopenia, bradycardia, and fatal cardiac arrhythmias

Toxicology in India frequently involves substances used for the adulteration of food. Adulterants are substances added to food or oils to increase volume or reduce cost, often leading to widespread clinical outbreaks.

Argemone mexicana

• Context
  • Also known as yellow poppy or Mexican poppy
  • Used in the adulteration of mustard oil with argemone oil
• Active principles
  • Sanguinarine (primary toxin)
  • Dihydrosanguinarine
• Mechanism of action: toxic alkaloids interfere with pyruvate dehydrogenase → impaired pyruvate oxidation → capillary dilatation and increased permeability → epidemic dropsy
• Clinical features: bilateral pitting edema of the lower limbs, diarrhea, congestive heart failure, secondary open-angle glaucoma, erythema
• Detection test: addition of concentrated nitric acid to contaminated oil produces an orange-red/reddish-brown color

The Big Four snakes of India

The Indian subcontinent is home to several highly venomous snakes, with four species accounting for the majority of clinically significant envenomations. Venomous snakes are categorized by their primary toxic effect: neurotoxic (elapidae) or haemotoxic (viperidae).

Clinical presentation

• Fear: most common manifestation
• Dry bite: fang marks may be visible, but no progressive local or systemic signs of envenomation
• Ophitoxemia
  • Local signs:
    • Progressive pain and swelling
    • Bleeding
    • Necrosis
    • Gangrene
    • Compartment syndrome
  • Hemotoxic signs
  • Neurotoxic signs

Clinical diagnostic tests

• 20-minute whole blood clotting test
  • A bedside test vasculotoxic/hemotoxic envenomation, especially by viperidae
  • Procedure:
    • Fresh venous blood is placed in a clean, new, dry glass test tube and left undisturbed for 20 minutes
    • Unclotted blood after 20 minutes indicates coagulopathy/vasculotoxic systemic envenomation
• Single breath count
  • Used in elapidae bites to assess impending respiratory failure
  • Patient is asked to take a deep breath and then count out loud at a steady pace of about two counts per second until they run out of breath
  • A count below 30 or a declining trend suggests impending respiratory failure and the need for assisted ventilation

Management of snake bites in India

• First Aid
  • Reassure the patient.
  • Remove tight items, immobilize the bitten limb with a splint, and keep the patient still
  • Transport urgently to the hospital
  • Report any systemic symptoms that developed during transport.
  • Ligation or incision of the bite site is strictly contraindicated.
• Anti-snake venom (ASV)
  • Polyvalent ASV in India is effective against all four major species.
  • Administered IV (typically 10 vials as standard initial dose) only if systemic envenomation is present
• Adjuvants: IV neostigmine with atropine is used to reverse neuromuscular paralysis in cobra bites.

Scorpions in India

Overview

• Scorpion envenomation in India is a significant clinical issue, primarily involving the Indian red scorpion and Indian black scorpion.
• The Indian red scorpion is the most medically significant in India.
• Black scorpions generally cause severe local pain but fewer systemic complications compared to the red variety.

Indian red scorpion (Hottentotta tamulus)

• Venom
  • Contains neurotoxins that prolong voltage-gated sodium channel opening
  • Causes a massive release of endogenous catecholamines → autonomic storm
• Autonomic storm
  • Cholinergic phase (early): vomiting, sweating, bradycardia, hypotension, and priapism
  • Adrenergic phase (late): hypertension, tachycardia, acute pulmonary edema, and myocardial dysfunction
• Treatment
  • Prazosin: the drug of choice to counteract the adrenergic effects
  • Antivenom: specific monovalent antivenom; most effective when given early and in combination with prazosin

Spanish fly (Lytta vesicatoria)

• Context
  • Also known as blister beetle
  • Dried beetle remains were traditionally called cantharides.
• Active principle: cantharidin, which is highly irritant to mucous membranes and the urinary tract
• Skin Exposure: local irritation with redness, burning sensation, and large blisters
• Oral Consumption
  • Gastrointestinal system: severe burning pain, haematemesis, and dysphagia
  • Urinary system: dull pain in the loins, hematuria, and intense nephrotoxicity
  • Behavioral: historically misused as an aphrodisiac, as it causes priapism in males due to urethral irritation, not true aphrodisiac action