Any measure that will reduce the incidence of paracetamol poisoning is to be welcomed. Hawton et al report the impact of legislation restricting pack sizes of paracetamol and salicylate on self poisoning, but there are major limitations in interpretation—for example, the period studied after the legislation came into force is too short (one year) for its impact to be fully assessed. This is particularly relevant in the assessment of patients with acute liver disease as the numbers are small and there will be baseline variability. The data from the liver unit at King's College Hospital cross the line indicating an incidence rate ratio of 1, and the data from Leeds, Newcastle, and the Royal Free Hospital have incidences close to zero.
The authors give data on blood paracetamol concentrations and mean number of tablets taken per paracetamol overdose, but these did not greatly change and would be the main determinant of outcome in early paracetamol poisoning. Certainly, prothrombin time would not be expected to be a good marker, not least because of the availability of adequate treatment with acetylcysteine.
Over the same period Donogue et al examined 2020 cases of deliberate paracetamol poisoning; they concluded that the incidence did not change after pack size was restricted in the Republic of Ireland. In addition, our data show that the pack size legislation is not complied with, at least in London, and considerably more than the restricted number of pills can be bought in pharmacies, supermarkets, and corner shops.
In conclusion, restrictions on pack size are not being adhered to universally. It is too early to make any causal conclusions on their impact on either the incidence of paracetamol poisoning in general or acute liver failure in particular.