Study finds common antihistamine may worsen MS progression

Antihistamine clemastine may accelerate disease progression in people with progressive multiple sclerosis (MS), a new study has found.

Clemastine is an antihistamine often used to treat hay fever and other allergies. It has shown some promise in encouraging remyelination – the process of rebuilding the protective layer around nerve fibres – particularly in people with MS who experience optic nerve damage.

However, a recent clinical trial led by researchers at the University of California, San Francisco, looked more closely at the long-term effects of clemastine in people with MS. It was part of the TRAP-MS trial, which is looking at many different possible treatments for MS. Nine patients were assigned to the clemastine part of the trial.

Those who took clemastine showed more changes on MRI scans that indicate brain tissue loss and disease progression, compared to those who did not take the drug. Participants on clemastine also had worse outcomes on disability scales, though the sample size was small. The clemastine arm of the trial was halted due to these results.

In addition to boosting disability progression, most of the clemastine-treated patients experienced an increase in body weight, total cholesterol, low-density lipoprotein (LDL) cholesterol, or the “bad” cholesterol, and CRP, a marker for body-wide inflammation. These changes were not seen with the other drugs tested.

These findings highlight the complexity of developing treatments for MS – especially those aimed at repairing damage to the nervous system. Clemastine is not currently licensed to treat MS, but this study will likely influence future research and clinical guidance on its use.

People with MS are advised not to start or stop any medication without consulting their healthcare team.