The effect of recalling paracetamol on hospital admissions for poisoning

To the Editor: Paracetamol availability is an important public health issue. Kisely et al have further investigated the impact of two paracetamol recall periods on analgesic poisoning using a dataset derived from hospital admissions.1 We are concerned about the robustness of data that uses ICD codes, because of significant coding problems that occur with poisoning admissions.

The aim of their study was as a follow-up to our own,2 to look at the impact of removing paracetamol tablets from the shelf during a recall period. Availability is reported to be the most common reason for patients choosing to take paracetamol in overdose3 and, as such, has the potential to affect acute deliberate self-poisoning. However, Kisely et al recognised that it was difficult for them to distinguish between intentional and unintentional ingestions because of the limitations of their dataset1 and hence they considered both of these together. This is inappropriate if the aim is to assess the effect of availability on paracetamol deliberate self-poisoning. For example, there is no evidence that presentations with therapeutic errors in dosing are related to availability and these should be excluded. This is not possible by using ICD codes and was therefore not done by Kisely et al.1

In addition, it is only relevant to include accidental ingestions of tablet formulations of paracetamol, because only these were affected by the recall. There are significant numbers of presentations of children, who accidentally ingest liquid formulations of paracetamol (hence not related to the recall period), that are coded as paracetamol admissions. This introduces a further significant potential bias in the Kisely study.

A more concerning problem is the reliability of ICD coding in separating out different analgesics. Poisoning with prescription products such as paracetamol-codeine combination analgesics, which were not affected by the recall period, are also likely to be included in the study being coded as T39.1 (paracetamol overdoses).1

There are significant limitations in using ICD codes, resulting in the dataset analysed not being a true reflection of the impact of the recall of paracetamol tablets. Our study took into account only tablet formulations of the paracetamol alone compounds.2 Paracetamol ingestions following therapeutic error were excluded and accidental ingestions of only tablet formulations were included. While the numbers in the study were small for the hospital presentations, the data set for the NSW Poisons Information Centre was much larger and showed significant increases in intentional and accidental ingestions of ibuprofen, the next most available analgesic.2

In an environment where paracetamol restriction is a hotly debated topic, particularly in light of recent coroners’ cases, it is vital to consider the impact of paracetamol restriction on all types of deliberate self-poisoning by using an appropriate dataset that reflects the measures taken to reduce availability. The challenge for state and federal health departments is to fund appropriate postmarketing toxicovigilance for accidental and intentional self-poisoning in order to clarify these important public health issues.