Unintended hepatic injury associated with the use of paracetamol (acetaminophen)-containing products has been growing.  The aim of the study was to seek a better understanding of the causes of this observation in order to evaluate the potential impact of proposed preventive measures.

The study involved retrospective analysis of the National Poison Data System database for 2000-07 involving exposures to paracetamol and an opioid, containing prospectively collected patient exposure data, clinical symptomatology and outcome.  This dataset was limited to non-suicidal cases in patients 13 years of age and older.  For comparison, the parallel, mutually exclusive dataset involving exposures to one or more non-opioid containing paracetamol products was analysed.

Hepatic injury associated with paracetamol use is increasing significantly faster than population, paracetamol product sales and poison centre use.  This suggests a growing portion of consumers is self-dosing paracetamol beyond the toxic threshold.  This is true for paracetamol with and without opioids, but the increase in hepatic injury is greater when paracetamol is taken with an opioid.  This disproportionate rise is greatest with misuse and abuse of paracetamol products in combination with opioids.  Increasing self-dosage of the opioid combination products for the opioid effect is likely to result in more cases of toxic exposure to paracetamol.  In contrast, cases of exposure to paracetamol-containing cough and cold products are underrepresented among those injured.  In the absence of opioid-containing products, consumption of more than one paracetamol-containing product did not contribute to injury.  Efforts to modulate unintentional paracetamol-related hepatic injury should consider these associations. (18 refs.)