Toxicity of Common Drugs

Overview – Toxicity of Common Drugs

Toxicity of common drugs is a high-yield topic in clinical toxicology, especially for emergency and general medicine. It includes the identification of toxidromes, initial management of poisoned patients, and understanding the mechanisms, symptoms, and treatments for common toxic agents like paracetamol, antidepressants, and digoxin. Early recognition and appropriate intervention can be lifesaving in overdose scenarios.

Initial Approach to the Poisoned Patient

Key Steps:

  • Resuscitation & Stabilization
  • History & Physical Examination
    • Look for toxidromes (symptom patterns indicating specific toxins)
  • Decontamination
    • GI, skin, eye decontamination as appropriate
  • Investigations
    • Labs, ECG, radiology
  • Antidotes
    • Use if specific agent identified
  • Enhanced Elimination
    • Only for selected drugs (e.g., dialysis, multiple charcoal doses)

Decontamination

  • Activated Charcoal (PO)
    • Most effective if given within 1 hour
    • Multiple doses for drugs with enterohepatic circulation:
      • Carbamazepine, Phenobarbitone, Quinine, Theophylline

Toxidromes

Anticholinergic Toxidrome

  • Symptoms: Blurred vision, choreoathetosis, dilated pupils, flushing, urinary retention
  • Complications: Hypertension, hyperthermia, tachycardia
  • Common drugs: Atropine, Tricyclic antidepressants

Cholinergic Toxidrome

  • Symptoms: Lacrimation, salivation, defecation, diarrhoea, vomiting
  • Complications: Bradycardia
  • Common drugs: Organophosphate pesticides (AChE inhibitors)

Hallucinogenic Toxidrome

  • Symptoms: Hallucinations, disorientation, panic, seizures
  • Complications: Hypertension, tachycardia, tachypnea
  • Common drugs: Amphetamines, Cocaine, Phencyclidine (PCP)

Opiate Toxidrome

  • Symptoms: Altered consciousness, dysphoria, unresponsiveness
  • Complications: Bradycardia, hypotension, hypothermia, respiratory depression
  • Common drugs: Morphine, Fentanyl, Oxycodone

Sedative/Hypnotic Toxidrome

  • Symptoms: Confusion, delirium, ataxia, coma
  • Complications: Apnoea
  • Common drugs: Benzodiazepines, Barbiturates, Antiepileptics, Ethanol

Sympathomimetic Toxidrome

  • Symptoms: Sweating, hyperreflexia, anxiety
  • Complications: Hypertension, tachycardia
  • Common drugs: Amphetamines, Cocaine, Ephedrine, Tyramine (with MAOIs)

Common Drug Toxicities

Paracetamol Poisoning

  • Toxic Mechanism: NAPQI metabolite → hepatotoxic when glutathione depleted
  • Investigations: Paracetamol levels, LFTs
  • Management:
    • Activated charcoal (if early)
    • N-acetylcysteine or Methionine (glutathione precursors)
Paracetamol Poisoning
https://commons.m.wikimedia.org/wiki/File:Paracetamol_metabolism.svg

Digoxin Toxicity

  • Used for: CHF, SVT
  • Toxic Effects:
    • Cardiac: Arrhythmias, syncope
    • CNS: Confusion, hallucinations
    • GI: Vomiting, anorexia
  • Risk Factors: Renal failure, hypokalaemia, drug interactions
  • Management:
    • Activated charcoal
    • Digoxin-specific Fab antibodies
    • Electrolyte correction (K+, Mg2+)
    • Manage arrhythmias: Atropine, pacing, defibrillation as needed
toxicity of common drugs: Digoxin Poisoning

Aspirin (Salicylate) Poisoning

  • Complications:
    • Reye’s syndrome in infants
    • Chronic toxicity in elderly: Encephalopathy, hyperventilation, pulmonary oedema
  • Salicylism Symptoms: Tinnitus, vomiting, delirium, seizures
  • Management:
    • Activated charcoal
    • Whole-bowel irrigation (enteric-coated)
    • Sedation, intubation, and mechanical ventilation for CNS symptoms
toxicity of common drugs: Aspirin
Source: http://www.emdocs.net/em3am-salicylate-overdose/

Laxative Toxicity

  • At-risk groups: Children, eating disorder patients, elderly
  • Stimulant Laxatives:
    • Acute: Vomiting, diarrhoea, shock (severe)
    • Chronic: Electrolyte imbalance, hypokalaemia, GI dysfunction
  • Osmotic Laxatives: Hypocalcaemia → lethargy, carpopedal spasm
  • Herbal/Mineral oil laxatives: Risk of lipoid pneumonia
  • Management:
    • Activated charcoal
    • Correct fluids/electrolytes
    • Fibre and fluid intake
    • Psychiatric referral if abuse suspected

Antidepressant Toxicity

Tricyclic Antidepressants (TCAs)

  • Symptoms: Delirium, arrhythmias, seizures, hypotension
  • Management:

SSRIs (Selective Serotonin Reuptake Inhibitors)

  • Acute Toxicity: Drowsiness
  • Serotonin Syndrome:
    • Agitation, myoclonus, hyperreflexia, hyperthermia, GI upset
  • Management:
    • Activated charcoal
    • Benzodiazepines
    • IV fluids and cooling

Summary – Toxicity of Common Drugs

Toxicity of common drugs encompasses a spectrum of overdose presentations including toxidromes, metabolic derangements, and organ damage. Key agents such as paracetamol, digoxin, aspirin, antidepressants, and laxatives all have distinct clinical features and treatments. Recognising these patterns quickly can prevent complications and save lives. For a broader context, see our Pharmacology & Toxicology Overview page.

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