Almost a quarter of GPs are prescribing an ‘unsafe’ strength of the immunosuppressant methotrexate, a new study has found.
Methotrexate, which is commonly prescribed for conditions such as rheumatoid arthritis, Crohn’s disease, severe psoriasis and some cancers, presents a ‘particularly high risk of accidental overdose’ due to being taken just once weekly, the study said.
The British National Formulary (BNF) recommends that GPs prescribe patients with only a single strength of methotrexate tablets of ‘usually’ 2.5mg.
However, researchers from the Nuffield Department of Primary Care Health Sciences at the University of Oxford found that 23% of over 7,000 GP practices in England still co-prescribed different methotrexate strengths according to the latest available data.
The study, published in the BJGP today, said: ‘Of 7,349 practices in England, 1,689 prescribed both 2.5mg and 10mg tablets to individual patients in 2017, breaching national guidance.’
However, an analysis of all prescriptions dispensed between August 2010 and April 2018 showed that the prescribing of the 10mg tablets fell from 9% of all methotrexate tablets in 2010 to just 3% in 2018.
The study also found a ‘substantial variation’ in methotrexate prescribing between CCGs and that practices with a high QOF score had lower rates of prescribing 10mg tablets, while practices in urban areas were ‘especially likely’ to have high 10mg prescribing rates.
Dr Ben Goldacre, director of the dataLab in the Nuffield Department of Primary Care Health Sciences, said that ‘unsafe methotrexate prescribing remains common, with substantial variation between GP practices’.
However, he added that GPs are ‘often overwhelmed with guidance’.
Lead author Brian MacKenna recommended that GPs should ‘review their prescribing’ of methotrexate and begin switching patients away from 10mg tablets.
He said: [I’d encourage every GP to] see if they are prescribing a lot of 10mg tablets and quite simply I would say stop, discuss with your patients [and] with your local pharmacies about switching people to 2.5mg.’
Further research is ongoing into how computer systems impact GP prescribing decisions, he added.
Meanwhile, the NHS must invest in ‘better strategies’ around implementation of the guidance, including audits and ‘targeted dissemination’ of safety information, the researchers recommended.