Which common substances should I consider in the differential diagnosis of an overdose in adults?

Guideline-aligned answer with reasoning, red flags and references. Clinically reviewed by Dr Kola Tytler MBBS CertHE MBA MRCGP.

Posted: 22 August 2025Updated: 22 August 2025 Guideline-Aligned (High Confidence) Clinically Reviewed
Dr Kola Tytler MBBS CertHE MBA MRCGPClinical Lead • iatroX

In the differential diagnosis of overdose in adults, common substances to consider include analgesics such as paracetamol and non-steroidal anti-inflammatory drugs (NSAIDs), sedative-hypnotics including benzodiazepines and barbiturates, opioids, antidepressants (particularly tricyclic antidepressants), antipsychotics, cardiovascular drugs like beta-blockers and calcium channel blockers, and substances of abuse such as alcohol and recreational drugs (e.g., cocaine, amphetamines) . Additionally, toxic alcohols (methanol, ethylene glycol), heavy metals, and household chemicals should be considered depending on the clinical context . The clinical presentation often guides the suspicion of specific agents, but a broad consideration of these common substances is essential for accurate diagnosis and management .

Key substances to consider include:

  • Paracetamol and NSAIDs
  • Benzodiazepines and barbiturates
  • Opioids
  • Tricyclic antidepressants and other antidepressants
  • Antipsychotics
  • Cardiovascular drugs (beta-blockers, calcium channel blockers)
  • Alcohol and recreational drugs (cocaine, amphetamines)
  • Toxic alcohols and household chemicals

These substances are frequently implicated in overdose cases and should be systematically considered during assessment to guide appropriate investigations and treatment .

Educational content only. Always verify information and use clinical judgement.