Clinical Guides
Approach to Poisoning
A clinically focused emergency approach to suspected poisoning in India, covering resuscitation, toxidromes, focused diagnostics, limited decontamination, selected antidotes, pesticide and corrosive exposures, poison-centre support, safeguarding and medicolegal documentation.
MedNext Academy | 13 min read
Approach to Poisoning
A clinically focused emergency approach to suspected poisoning in India, covering resuscitation, toxidromes, focused diagnostics, limited decontamination, selected antidotes, pesticide and corrosive exposures, poison-centre support, safeguarding and medicolegal documentation.
Summary
Poisoning is a dynamic clinical syndrome caused by a medicine, chemical, pesticide, plant, gas, venom or other exposure. The container may be wrong, the history incomplete and early examination deceptively normal. Management therefore starts with physiology: protect staff from contamination, assess airway, breathing, circulation, disability and temperature, correct hypoglycaemia, monitor the heart, and treat seizures, hypoxaemia, shock or dangerous dysrhythmia before waiting for toxicology confirmation. Contact a recognised poison information service or clinical toxicologist early for an unknown, severe or unusual exposure.
A focused history asks what, how much, by which route, when, where and why, while identifying co-ingestants, formulations, body weight, comorbidity and pre-hospital treatment. Toxidromes narrow the field but are patterns rather than diagnoses. Bedside glucose, ECG, electrolytes, renal and liver function, blood gas and pregnancy testing often change care. Calculate anion and measured osmolal gaps only with their limitations understood; normal gaps do not reliably exclude toxic alcohol exposure.
Gastrointestinal decontamination is selective. Do not induce vomiting. Activated charcoal has a time- and toxin-dependent role only when potential benefit exceeds aspiration and procedural risk; it does not bind every poison. Gastric lavage is not routine. Corrosives and hydrocarbons require different precautions. Antidotes supplement, not replace, supportive care. Indian practice must anticipate agricultural pesticides, delayed rural transfer, product mixtures and limited assay availability. Every intentional exposure requires compassionate suicide-risk assessment and a safe disposition. Clinical care takes priority while preserving labels, samples and contemporaneous medicolegal documentation. This draft has been reviewed by the MedNext Clinical Team and is not a treatment protocol.
How Common Is It?
Poisoning burden varies substantially by geography, age, occupation, pesticide regulation, medicine access, case definition and whether surveillance counts calls, admissions or deaths. Indian hospital series commonly report pesticide, pharmaceutical, household chemical, corrosive and plant exposures, but their proportions reflect local agriculture and referral systems. A tertiary toxicology unit cannot provide a national incidence estimate, and a rural pesticide cohort should not be applied to an urban emergency department. This guide therefore avoids an unsupported single annual death or admission count.
The clinically relevant pattern is heterogeneity. Deliberate self-poisoning may involve readily available agricultural products in farming communities and pharmaceuticals elsewhere. Accidental exposures are prominent in young children. Occupational dermal or inhalational pesticide exposure, carbon monoxide exposure, medication errors, substance use and envenomation create different prevention and management needs. Product names are unreliable because formulations and concentrations change, counterfeit or decanted chemicals occur, and one brand may contain several active agents.
WHO guidance treats highly hazardous pesticides and self-poisoning as a preventable public-health problem, while poison-control systems provide surveillance, treatment advice and prevention intelligence. The individual clinician should use local case mix to set readiness: airway and ventilation capability, atropine access, N-acetylcysteine availability, ECG monitoring, safe decontamination space and referral arrangements. Frequency never determines urgency. A rare sodium-channel-blocking overdose may be more immediately lethal than a familiar sedative ingestion, and an apparently mild corrosive exposure may evolve. Severity comes from the substance, dose, route, timing, host and observed physiology, not from how common the poison is.
Risk Factors
Risk is shaped by exposure opportunity and vulnerability. Deliberate self-harm risk rises with mental illness, prior attempts, acute interpersonal or financial crisis, substance use, chronic pain, impulsivity and access to toxic products. These are prompts for sensitive assessment, not stereotypes. Agricultural workers may handle concentrated pesticides without adequate storage, labelling or personal protective equipment. Children are vulnerable to medicines or chemicals stored in drink bottles, unlocked cupboards or unlabelled containers. Older adults face polypharmacy, dosing errors, renal impairment and drug interactions.
Clinical severity depends on dose relative to body weight, sustained-release or enteric-coated formulation, co-ingestion, delayed presentation and route. Pre-existing cardiac disease increases vulnerability to conduction disturbance; respiratory disease and frailty reduce tolerance of aspiration or hypoventilation. Liver disease may worsen risk from hepatotoxic agents, and impaired renal function delays elimination of lithium, salicylate and other toxins. Pregnancy introduces maternal and fetal considerations without changing the priority of maternal resuscitation.
Specific history changes probability: pesticide spraying suggests inhalational or dermal cholinergic exposure; an empty blister pack suggests pharmaceutical overdose but does not prove ingestion; smoke exposure in an enclosed space raises carbon monoxide and cyanide concern; access to paracetamol, sedatives, opioids, tricyclic antidepressants or cardiovascular drugs guides targeted assessment. Corrosives in household cleaning products can injure the airway and gastrointestinal tract. Intent may remain uncertain after accidental, recreational or assault-related exposure. Prior induced vomiting, unprotected lavage or unverified traditional remedies can add aspiration, caustic or interaction risk. Always consider safeguarding, coercion, occupational exposure of others and contamination of accompanying family or staff.
Diagnosis
History
Obtain information from the patient, relatives, ambulance staff, workplace and product packaging without delaying resuscitation. Record exact product and active ingredients, strength, maximum possible quantity, route, time, formulation, co-ingestants and treatment already given. Ask about regular medicines, allergies, body weight, pregnancy, kidney or liver disease and intent. A photo of the label can help a poison centre, but tasting or smelling an unknown product is unsafe. Establish the last known well time and whether symptoms are improving or evolving.
Examination
Use an ABCDE sequence and repeat it. Record consciousness, pupils, respiratory rate and pattern, oxygen saturation, heart rate, blood pressure, temperature, capillary refill and glucose. Look for secretions or dryness, sweating, flushing, bowel activity, urinary retention, fasciculation, rigidity, clonus and skin patches. Examine the mouth for corrosive injury but recognise that absent oral burns do not exclude deeper injury. Remove contaminated clothing with appropriate protective equipment and prevent secondary exposure. A toxidrome may be incomplete after mixed ingestion or treatment.
Investigations
Obtain bedside glucose and a 12-lead ECG early; repeat ECGs when delayed cardiotoxicity is plausible. Tests commonly include electrolytes, bicarbonate, creatinine, liver tests, blood gas, lactate, full blood count and pregnancy testing. Measure paracetamol concentration in intentional or uncertain pharmaceutical ingestion according to timing and local protocol. Add salicylate, lithium, digoxin, toxic alcohol, carboxyhaemoglobin or cholinesterase tests only when relevant and available. Calculate anion gap with the laboratory reference range and interpret osmolal gap as time-dependent and nonspecific. Chest imaging, creatine kinase, coagulation studies and serial organ tests follow the syndrome. Broad urine drug screens rarely identify severity or exclude dangerous substances.
Differential Diagnosis
Toxidromes organise bedside reasoning. Cholinergic poisoning produces bronchorrhoea, wheeze, salivation, lacrimation, vomiting or diarrhoea, urination, miosis, bradycardia or tachycardia, fasciculation and weakness; pesticide mixtures and carbamates can modify the picture. An opioid syndrome combines depressed consciousness and ventilation with usually small pupils, but hypoxia, co-ingestion and some opioids alter pupil size. Sedative-hypnotic exposure generally causes central nervous system and respiratory depression without the marked secretions of cholinergic poisoning.
Anticholinergic poisoning produces delirium, mydriasis, dry flushed skin, hyperthermia, tachycardia, urinary retention and reduced bowel sounds. Sympathomimetic exposure also causes agitation, mydriasis, tachycardia and hyperthermia, but sweating and heightened bowel sounds help distinguish it. Serotonin toxicity is supported by serotonergic exposure, clonus and hyperreflexia; neuroleptic malignant syndrome more often evolves with lead-pipe rigidity after dopamine antagonism. Sodium-channel blockade may present with seizures, hypotension and a broad QRS.
Non-toxicological mimics must remain active: hypoglycaemia, sepsis, stroke, meningitis, head injury, post-ictal state, diabetic or alcoholic ketoacidosis, hepatic or uraemic encephalopathy, heat illness and primary psychiatric disease. A high anion-gap acidosis can reflect lactate, ketones, renal failure, salicylate or toxic alcohols. An osmolal gap may rise from ethanol, ketoacidosis or laboratory variation and can normalise as toxic alcohol is metabolised. Corrosive injury, aspiration and pulmonary oedema can explain respiratory findings after ingestion. Mixed poisoning is common; finding one agent does not close the differential or remove the need to investigate unexpected physiology.
Management
Begin with scene and staff safety. Move away from fumes when safe, use appropriate protective equipment, remove contaminated clothing and irrigate exposed skin or eyes with water according to substance-specific advice. Secure the airway when protective reflexes or ventilation are failing, anticipating secretions, vomiting and difficult laryngoscopy. Give oxygen for hypoxaemia or indicated inhalational poisoning, support ventilation, establish vascular access, treat hypoglycaemia and control seizures with an evidence-based emergency regimen. Use ECG findings and haemodynamics to guide toxin-specific resuscitation while seeking expert advice.
Do not induce emesis. Activated charcoal is considered mainly for a potentially toxic, charcoal-binding ingestion presenting early with an intact or protected airway; its benefit declines with time and the aspiration risk can outweigh benefit. It is ineffective for substances such as alcohols, metals and many corrosives. Gastric lavage should not be routine and, if exceptionally considered for a life-threatening recent ingestion, requires toxicology advice, airway protection and trained staff. Whole-bowel irrigation has narrow indications. Corrosive ingestion is not treated by neutralisation, vomiting or blind tube insertion; prioritise airway, analgesia, nil-by-mouth decisions and early endoscopy or surgical consultation.
Selected antidotes include naloxone titrated to adequate ventilation for opioid toxicity, N-acetylcysteine for clinically indicated paracetamol exposure, atropine titrated to respiratory secretions and perfusion in organophosphate poisoning, and sodium bicarbonate for clinically significant sodium-channel blockade. Oximes, fomepizole or ethanol, digoxin immune Fab and other antidotes require agent-specific expertise and availability. Enhanced elimination, including haemodialysis, is poison- and severity-specific. Observe for delayed toxicity, complete mental-health and safeguarding assessment, and ensure a documented follow-up plan before discharge.
Prescribing Information
Antidote dosing must use a current local protocol, verified weight, formulation and route. Naloxone is titrated to restore adequate ventilation rather than necessarily full alertness; its duration may be shorter than the opioid, so recurrent respiratory depression requires observation, repeat dosing or infusion. Abrupt reversal can precipitate withdrawal and agitation. Flumazenil is not routine for an undifferentiated sedative overdose because seizure and withdrawal risk is important, particularly with chronic benzodiazepine use, pro-convulsant co-ingestion or an abnormal ECG.
N-acetylcysteine should not be delayed when paracetamol hepatotoxicity risk is established or results will be unavailable beyond a safe treatment window. The Rumack-Matthew nomogram applies only to a single acute ingestion with a known time and an appropriately timed concentration; it does not safely interpret staggered, repeated supratherapeutic, unknown-time or modified-release exposure. Monitor liver tests, INR, renal function, glucose, acid-base status and clinical course according to protocol. Hypersensitivity-type reactions to intravenous N-acetylcysteine are managed without losing sight of the antidote's benefit.
In organophosphate poisoning, atropine is titrated to clearing bronchial secretions, improved air entry and adequate circulation, not to pupil size or a fixed total dose. Large cumulative doses and infusion may be required, with reassessment for recurrent cholinergic features or atropine toxicity. Oxime choice and timing depend on compound, severity and local policy; evidence is less uniform than for atropine and supportive ventilation. Sodium bicarbonate for QRS widening requires serial ECG, pH, sodium and potassium monitoring. Avoid a memorised antidote list detached from physiology, contraindications and poison-centre advice. Every medication order should state indication, endpoint, monitoring and escalation plan.
When to Refer
Transfer urgently to a centre with airway, critical-care and toxicology capability when there is respiratory depression, bronchorrhoea, hypoxaemia, shock, dysrhythmia, QRS or QT abnormality, seizure, severe agitation or hyperthermia, metabolic acidosis, evolving organ failure, corrosive injury, a high-risk agent, delayed-release formulation or uncertain large exposure. Early referral is preferable to deterioration during transport. Stabilise within local capability, send the container or clear label image safely, and communicate treatments and trends to the receiving clinician.
Call a recognised poison information centre or clinical toxicologist for unknown products, pesticide mixtures, uncommon antidotes, toxic alcohols, heavy metals, sustained-release medicines, enhanced elimination decisions, pregnancy, paediatric exposures or discordance between history and physiology. A poison-centre discussion is an adjunct to resuscitation and does not transfer clinical responsibility. If network access is unreliable, facilities should maintain current local contact routes and referral protocols rather than depend on an unverified number embedded in static content.
Corrosive exposure needs early gastroenterology, ENT, anaesthesia or surgical input according to airway and gastrointestinal findings. Acute liver failure after paracetamol requires specialist hepatology and transplant-centre discussion. Severe kidney injury or dialysable poison requires nephrology. Every intentional self-poisoning needs mental-health assessment once medically stable, safe observation, removal of immediate means where lawful and collaborative safety planning. Children, vulnerable adults, occupational clusters and suspected coercion or assault require safeguarding escalation. Document why discharge is safe; normal initial observations alone do not justify discharge before the relevant toxicity window has passed.
Red Flags
Airway and breathing red flags include stridor, voice change, drooling, facial or oral swelling, copious secretions, silent chest, cyanosis, falling respiratory rate, rising carbon dioxide, aspiration or progressive weakness. Circulatory danger includes hypotension, poor perfusion, severe hypertension, bradycardia, ventricular dysrhythmia, broad QRS, marked QT prolongation or recurrent syncope. Neurological danger includes coma, seizure, severe agitation, delirium, clonus, rigidity or rapidly rising temperature. Treat the physiology while identifying the poison.
Laboratory red flags include refractory acidosis, rising lactate, hypoglycaemia, hyperkalaemia, worsening creatinine, increasing aminotransferases or INR, methaemoglobinaemia or a concerning toxin concentration. A normal anion or osmolal gap does not exclude poisoning. Paracetamol exposure with unknown timing, repeated supratherapeutic dosing or delayed presentation cannot be dismissed using the standard nomogram. After pesticide exposure, recurrent secretions, muscle weakness or ventilatory failure may appear after initial improvement.
Corrosive red flags are airway symptoms, chest or abdominal pain, persistent vomiting, haematemesis, peritonism or systemic instability; the mouth can appear normal despite internal injury. Hydrocarbon aspiration may evolve after initial coughing. Aluminium phosphide and other fumigants can produce rapidly refractory cardiovascular collapse and secondary staff exposure from phosphine gas, so decontamination and ventilation precautions matter. Any intentional exposure with ongoing suicidal intent, inability to ensure supervision, violence, coercion or unsafe home access is a disposition red flag. Unexpected deterioration should trigger renewed ABC assessment, repeat ECG and glucose, reconsideration of co-ingestion, and immediate expert escalation.
Indian Clinical Context
Indian clinicians may encounter organophosphate or carbamate insecticides, aluminium or zinc phosphide products, pyrethroids, household corrosives, sedatives, paracetamol, rodenticides and toxic plants, with important regional variation. A product's trade name does not establish its ingredient: inspect the label, concentration and formulation and seek poison-centre help. Agricultural exposures may involve solvents or multiple active compounds. Phosphide poisoning has no established specific antidote; proposed oils, magnesium strategies and other interventions have inconsistent evidence and must not displace aggressive supportive critical care. Avoid unvalidated lavage recipes that generate gas or cause aspiration.
Atropine availability, ventilator capacity, dialysis, toxin assays and endoscopy differ between primary centres, district hospitals and medical colleges. The first facility should focus on staff safety, airway and breathing, glucose, ECG, resuscitation, limited appropriate decontamination and early transfer. The National Poisons Information Centre at AIIMS is one recognised Indian resource; facilities should verify current contact details locally, and regional poison centres may be more accessible. Telephonic advice should include age, weight, product, time, route, maximum dose, observations, ECG and treatments.
Treat suspected self-harm without blame. Mental-health assessment, family involvement with consent and safety, restriction of access to highly hazardous products, and follow-up are part of poisoning care. Medico-legal classification and police notification follow applicable law and institutional policy; they must not delay emergency treatment. Preserve containers, labels and samples with correct identity and chain-of-custody when required, record who supplied the history, and document exact times and interventions. Provide instructions in an understood language and account for transport distance, cost, recurrent toxicity and limited household supervision.
NMC Competency Mapping
Poisoning teaching integrates emergency medicine, pharmacology, forensic medicine, psychiatry and community medicine. The learner should demonstrate an ABCDE assessment, recognise failure of ventilation or circulation, check glucose, obtain an ECG, identify common toxidromes and construct a focused exposure history. They should explain why diagnosis is often clinical, why broad toxicology screens have limits, and when targeted concentrations or serial organ tests change treatment. Calculating anion gap is a reasoning skill; interpreting it without timing and differential context is not.
Pharmacology competencies include dose-response, toxicokinetics, antidote mechanisms, enhanced elimination and adverse effects. Students should know the principles of naloxone, N-acetylcysteine, atropine, oximes and sodium bicarbonate while recognising that current protocols determine dosing. Forensic competencies include contemporaneous documentation, preservation and labelling of relevant material, consent, applicable reporting duties and the distinction between clinical and evidentiary samples. Psychiatry competencies require compassionate suicide-risk assessment and safe disposition after medical stabilisation.
Community learning includes household and occupational prevention, safe pesticide storage, child-resistant packaging, poison-centre systems and restriction of highly hazardous means. Practical skills such as airway management, gastric procedures, antidote infusion, endoscopy and dialysis require supervised training and authorised practice; reading this guide does not confer competence. The NMC curriculum is an educational map, not a substitute for the receiving hospital's toxicology protocol, formulary, medicolegal policy or senior clinician. A safe learner communicates uncertainty early and never delays resuscitation to complete documentation or identify an exact poison.
Key Exam Pearls for NEET PG
Toxidromes are pattern-recognition aids. Cholinergic poisoning causes wet secretions, bronchospasm or bronchorrhoea, miosis, gastrointestinal activity, fasciculation and weakness; atropine endpoints are a clearer chest and adequate circulation, not pupil dilation. Opioid toxicity is treated by restoring ventilation with naloxone and observing for recurrence. Anticholinergic and sympathomimetic syndromes share mydriasis and agitation, but dry skin and reduced bowel activity favour anticholinergic exposure, whereas sweating and hyperreflexia favour sympathomimetic or serotonergic states.
A broad QRS after a compatible overdose suggests sodium-channel blockade and supports sodium bicarbonate with serial monitoring. Correct glucose before attributing coma to poison. The anion gap equals sodium minus chloride plus bicarbonate in the convention used locally; albumin and laboratory method affect interpretation. Osmolal gap is neither sensitive nor specific for toxic alcohols and changes over time. The paracetamol nomogram is restricted to a single acute known-time ingestion with a correctly timed level; N-acetylcysteine remains beneficial when indicated even after the ideal early window.
Activated charcoal is selective, time-dependent and unsafe with an unprotected airway. Gastric lavage and induced vomiting are not routine. Never neutralise a corrosive or pass a tube blindly. Organophosphate management combines decontamination, oxygenation, ventilation, atropine and selected oxime use; cholinesterase values support but do not replace clinical treatment. Aluminium phosphide causes severe shock and dysrhythmia without a proven antidote. Flumazenil is not the default for undifferentiated coma. In every deliberate exposure, the correct final step includes mental-health assessment and safe disposition.
Frequently Asked Questions
What should be done first when the ingested poison is unknown?
Protect staff from contamination and treat the patient, not the label: repeat ABCDE assessment, check glucose, obtain an ECG, support oxygenation and ventilation, control seizures and shock, and gather containers and collateral history. Use toxidromes to narrow possibilities, order targeted tests and contact a recognised poison information service or clinical toxicologist early.
When is activated charcoal appropriate after an acute ingestion?
It may be considered after a potentially toxic ingestion of a charcoal-binding substance, usually when presentation is early and the airway is intact or protected. It is not routine, does not bind every poison and can cause serious aspiration. The agent, time, formulation, dose and procedural risk should be discussed with toxicology guidance.
How is the paracetamol nomogram safely used in overdose assessment?
The nomogram applies to a single acute ingestion with a known time and a concentration taken at the appropriate post-ingestion interval. It does not safely handle unknown-time, staggered, repeated supratherapeutic or many modified-release exposures. When risk is established or results will be delayed, N-acetylcysteine should follow the verified local protocol without waiting for liver injury.
What are the essential discharge safeguards after intentional self-poisoning?
Discharge requires completion of the relevant medical observation period, stable physiology, review of delayed toxicity risk, mental-health and suicide-risk assessment, safeguarding where indicated, collaborative safety planning, responsible follow-up and a realistic plan to limit access to the substance. A normal early blood test or denial of intent alone is not sufficient.
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