In September 2012, the Medicines and Healthcare products Regulatory Agency (MHRA) substantially amended the Marketing Authorisation for acetylcysteine following an extensive review. The present study examined the impact of this license change on patterns of acetylcysteine use in patients presenting to hospital after paracetamol (acetaminophen) overdose. Between September 2011 and April 2013, 785 consecutive patients presented to York Hospital due to paracetamol overdose, and a before-after analysis was used to compare outcomes. There were 483 patients before and 302 patients after the license amendment, and age, gender, acute or staggered overdose pattern, and dose were similar in both groups. In the patients with paracetamol concentrations between the “100-line” and “200-line,” a significantly higher proportion received acetylcysteine treatment (51% before versus 98% after, ), as expected. A modest increase was also observed in relation to late or staggered overdose or cases where the time of ingestion was uncertain (53% versus 74%, ). The median duration of hospital stay increased across the entire study population, from 15 to 24 hours ( ) due to the increased proportion of patients requiring acetylcysteine treatment. The findings indicate that the MHRA amendment is a financially costly intervention, and further studies are needed to examine clinical outcomes so that its cost effectiveness might be addressed. 1. Introduction Acetylcysteine is well established as a safe and effective antidote for paracetamol poisoning, although there is uncertainty regarding the indications for treatment and most effective administration protocol [1–3]. A treatment nomogram was originally devised by Prescott to allow identification of patients at significant risk of acute liver injury, the so-called “200-line” plotted between 200？mg/L (1320？μmol/L) at 4 hours and 30？mg/L (200？μmol/L) at 15 hours [4]. As a modification, the “100-line” was plotted 50% lower so that treatment was indicated by lower paracetamol concentrations in patients with individual risk factors for paracetamol toxicity, such as malnourishment, chronic excess ethanol intake, or prior use of enzyme-inducing drugs [5–7]. These have long been established in clinical practice in the United Kingdom as “standard” and “high-risk” nomograms to indicate the need for acetylcysteine after acute paracetamol overdose. Other protocols have been adopted elsewhere, for example, the Rumack nomogram or “150-line” is used in the United States for all patients irrespective of individual risk factors and is plotted 25%
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