Medicines containing fluorine – a type of per- and polyfluoroalkyl substance (PFAS) often referred to as a ‘forever chemical’ – are not associated with higher rates of adverse drug reactions (ADRs), according to new research.
In a paper published in the journal PLOS One, researchers from the University of Birmingham reviewed five years of data between 2019 and 2024 from the MHRA Yellow Card scheme relating to 13 fluorinated medicines and six structurally similar non-fluorinated medicines.
Their analysis compared ADRs per one million items dispensed. The most frequently prescribed drug studied was the proton pump inhibitor lansoprazole, which showed the lowest rate of ADRs per one million items (n=14).
Leflunomide had the highest suspected ADRs per one million items dispensed (n=343) and yet contains the same number of fluorine atoms (n=3) and similar type of fluorine moiety as lansoprazole.
The anti-diabetic sitagliptin and antiarrhythmic flecainide, which contained the highest levels of fluorine, were not associated with the highest levels of ADRs.
The study found ‘no relationship’ between the number of fluorine atoms in a medicine and the number of ADRs reported.
The researchers found that most ADRs recorded for fluorinated drugs were outside the scope of side effects usually associated with PFAS. The comparison with non-fluorinated drugs suggested that the way the drug acted was more likely to result in that ADR, they concluded.
Dr Alan Jones, associate professor in medicinal and pharmaceutical chemistry at the University of Birmingham, and corresponding author of the paper, said: ‘Recent changes to the classification of PFAS means certain essential medicines are now deemed to contain forever chemicals.
‘In this study we explored adverse drug reactions reported to the MHRA Yellow Card scheme relative to their prescribing rate. Reassuringly, no statistical correlation between the fluorine content of the medicine and type of side effect emerged.’
The researchers noted, however, that the study was limited by the self-reported nature of Yellow Card data, which could lead to underreporting of ADRs.
A version of this article was originally published by our sister publication The Pharmacist.
