Differentials
Gammahydroxybutyrate (GHB)/gammabutyrolactone (GBL) overdose
SIGNS / SYMPTOMS
Most likely condition to mimic opioid overdose. Miosis may not be present.
INVESTIGATIONS
There may be no, or only a minimal, response to naloxone.
Clonidine/imidazolines overdose
SIGNS / SYMPTOMS
Presents with more profound bradycardia and hypotension than opioid overdose.
INVESTIGATIONS
Although patients may have a minor response to naloxone, most do not have a dramatic response.
Antipsychotic overdose
SIGNS / SYMPTOMS
Presents with hypotension and tachycardia, but will not have the profound bradypnoea seen in opioid overdose.
INVESTIGATIONS
No response to naloxone.
Pontine haemorrhage
SIGNS / SYMPTOMS
Presents with miosis, but other features of opioid overdose, such as bradypnoea, will not be present.
INVESTIGATIONS
No response to naloxone.
Ketamine overdose
SIGNS / SYMPTOMS
Central nervous system depression and miosis present in a minority of cases. Nystagmus is usually present and significant respiratory depression is absent, differentiating this from opioid overdose.
INVESTIGATIONS
No response to naloxone.
Phencyclidine (PCP) overdose
SIGNS / SYMPTOMS
Central nervous system depression and miosis present in a minority of cases. Nystagmus is usually present and significant respiratory depression is absent.
INVESTIGATIONS
No response to naloxone.
Alcohol intoxication
SIGNS / SYMPTOMS
Usually presents with altered mental state alone. Miosis and significant respiratory depression are absent.
INVESTIGATIONS
No response to naloxone; serum alcohol level will be positive.
Sedative hypnotic overdose
SIGNS / SYMPTOMS
Miosis not present.
INVESTIGATIONS
No response to naloxone.
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