UK guidance says methotrexate should generally be prescribed in a single strength of tablet, usually 2.5mg, to reduce the risk of harm from errors.
However, an analysis of data from 7349 GP practices in England from August 2010 to April 2018 has found that 1689 (23%) prescribed both 2.5mg and 10mg tablets to the same patient.
The analysis showed wide variation in the level of unsafe prescribing between practices, with 9.5% (n=697) of practices giving >14.3% of their methotrexate as 10mg tablets; and 1% (n=66) of practices giving >52.4% of their methotrexate as 10mg tablets.
The prescribing of 10mg tablets decreased over the study period, with 10mg tablets as a proportion of all prescribed methotrexate falling from 9.1% to 3.4%.
Between 1993 and 2017 there were 21 deaths attributed to methotrexate poisoning in England and Wales.
Dr Ben Goldacre, Director of the DataLab in the Nuffield Department of Primary Care Health Sciences at the University of Oxford, NHS doctor, and co-lead of the study, said: ‘Unsafe methotrexate prescribing remains common, with substantial variation between GP practices. We recognise that clinicians are often overwhelmed with guidance. We have therefore produced a free, publicly funded, openly accessible audit tool at OpenPrescribing.net.
This allows any clinician to easily review their own practice’s compliance. Our data updates every month so clinicians can track improvements over time.’