Clinical presentation

Effects of opioid poisoning include:

• respiratory effects
  • respiratory depression is common and the most important clinical sign of opioid toxicity; respiratory depression includes reduced minute volume, and reduced respiratory rate or apnoea
  • aspiration pneumonitis, pulmonary oedema
• central nervous system (CNS) effects
  • CNS depression, ranging from drowsiness to coma, frequently accompanies respiratory depression
  • serotonergic toxidrome, most likely with dextromethorphan, tramadol, pethidine, methadone, tapentadol
  • delayed-onset seizures with tramadol (common) and tapentadol (uncommon)
• ophthalmological effects—miosis is common, but not present in all patients and is not specific for opioid drug poisonings; many nonopioid drugs also cause miosis
• cardiovascular effects
  • QRS widening, atrioventricular (AV) nodal block and tachyarrhythmias with dextropropoxyphene¹
  • QT-interval prolongation and torsades de pointes with loperamide, methadone and oxycodone
• gastrointestinal effects—nausea, vomiting, constipation
• other effects—end-organ effects of hypoxia (eg myocardial ischaemia), rhabdomyolysis.