Kumar & Clark’s Clinical Medicine 10e by Adam Feather, David Randall, Mona Waterhouse Public health

Specific Poisons

12 Clinical Features and Management

  • Most cases result in minor gastrointestinal disturbances.

  • Severe cases may involve:

    • Coma

    • Convulsions

    • Acute kidney injury

  • Transient renal impairment is common post ibuprofen overdose.

Opiates and Opioids

Clinical Features

  • Cardinal signs of opiate poisoning include:

    • Pinpoint pupils

    • Reduced respiratory rate

    • Coma

  • Hypothermia, hypoglycaemia, and convulsions can occur in severe cases.

  • Non-cardiogenic pulmonary edema may arise in severe heroin overdoses.

Management

  • Intravenous naloxone can reverse respiratory depression and coma.

  • Initial dose: 1.2 mg, repeat as necessary.

  • Lower doses (0.4-0.8 mg) in less severe cases, caution in withdrawal cases.

  • Infusion of naloxone is often required due to its shorter action compared to overdosed opioids.

  • Manage non-cardiogenic pulmonary edema with mechanical ventilation.

Antidepressants: Tricyclics and SSRIs

Tricyclic Antidepressants (TCAs)

  • Mechanism: Block monoamine reuptake, increasing neurotransmitter levels.

  • Clinical Features:

    • Mild poisoning: Drowsiness, sinus tachycardia, dry mouth, dilated pupils.

    • Severe intoxication: Coma, convulsions, wide QRS interval on ECG, life-threatening arrhythmias.

  • Management:

    • Supportive care, potential ventilation, intravenous sodium bicarbonate for tachycardia.

Selective Serotonin Reuptake Inhibitors (SSRIs)

  • Generally safe, may still cause drowsiness, nausea, and bradycardia in overdose.

  • Management: Supportive therapy, monitor for serotonin syndrome. Venlafaxine can cause cardiac arrhythmias.

Benzodiazepines

Clinical Features

  • Overdose typically results in:

    • Drowsiness, ataxia, dysarthria, nystagmus

    • Severe cases: Coma and respiratory depression.

Management

  • Severe cases of respiratory depression need intravenous flumazenil (0.5-1.0 mg).

  • Caution in mixed overdoses and history of epilepsy.

Stimulants (Amphetamines, Cocaine, Synthetic Cathinones)

  • Clinical Features of Stimulants:

    • Dilated pupils, tachycardia, hyperthermia.

    • Severe cases cause: Agitation, paranoid delusions, seizures, cardiac arrhythmias.

    • Risks: Stroke, myocardial infarction, kidney injury.

  • Management:

    • Agitation: Diazepam (IV, 10-20 mg).

    • Hypertension: IV glyceryl trinitrate (start at 1-2 mg/h).

    • Control hyperthermia with cooling methods and consider dantrolene if severe.

Ethanol

Clinical Features

  • Features of intoxication include hypoglycemia, coma, hypothermia, metabolic acidosis.

Management

  • Supportive care; IV glucose for hypoglycaemia.

  • Haemodialysis for severe metabolic acidosis (if ethanol levels exceed critical thresholds).

Neuroleptics and Atypical Neuroleptics

Clinical Features

  • Impaired consciousness, hypotension, possible seizures; antimuscarinic effects.

Management

  • IV procyclidine for dyskinesia.

  • Correct acidosis and manage arrhythmias with magnesium.

Cannabis and Synthetic Cannabinoids

Clinical Features

  • Intoxication leads to euphoria, hallucinations, anxiety, and potential developmental issues in heavy users.

Management

  • Often requires reassurance; severe agitation could necessitate benzodiazepines or haloperidol.

Anticonvulsants

Clinical Features

  • Poisoning leads to lethargy, ataxia, coma; may require increased activated charcoal dosing for carbamazepine.

Other Drugs of Importance

  • Antidiabetic: Severely hypoglycemic effects possible from insulin/sulphonylureas.

  • Chloroquine: Severe presentations can lead to cardiac issues and hypokalaemia.

  • Organophosphates: Characterized by cholinergic symptoms; management includes removal and atropine.

Poisoning with Chemicals

Arsenic

  • Causes abdominal pain, vomiting, potential shock.

  • Management: Chelation therapy if indicated.

Carbon Monoxide

  • Sources: Poorly maintained heating systems; clinical features range from headache to coma.

  • Management: High-flow oxygen.

Cyanide

  • Causes hypoxia and potential cellular death; immediate oxygen and antidotes are required.

Poisons in the Natural World

Venomous Snakes

  • Key effects: swelling, bleeding disorders, paralysis.

  • Management focuses on timely hospital transport and supportive care.

Conclusion

  • Prompt identification and supportive management are critical for substance poisoning. Regular updates on local toxins and antidotes are recommended to minimize harm.