Clemastine (otherwise known as clemastine fumarate) is an over the counter antihistamine. Researchers are now investigating if it may help to promote myelin repair.

Find out more about clemastine

Clemastine is an active ingredient in antihistamines. It's also used to relieve itching associated with chickenpox or eczema. Clemastine enters the brain and causes drowsiness, so it is known as a sedating antihistamine.

Previous research in mice with an MS-like condition and a small clinical trial have shown that clemastine may promote myelin repair.

There's also some evidence from research with mice and from a very small study with healthy volunteers that clemastine may reduce immune activity.

As a tablet or liquid that is taken orally.

Metformin and clemastine trial

In September 2020 we announced our new clinical trial, which will be testing clemastine in a Phase 2a clinical trial in combination with metformin, a drug which is already used to treat type 2 diabetes.

This trial will recruit 50 participants with relapsing MS. Half will take a placebo (dummy drug) and the other half will take both metformin and clemastine. Researchers want to know if the combination of metformin and clemastine could repair myelin damage in relapsing MS.

Although both metformin and clemastine have been trialled in people with MS before, the effects of metformin on myelin repair in people has not been tested. And evidence from animal studies has shown that metformin enhances the effect of clemastine on myelin repair, but the two drugs have never been tested in combination.

The ReBUILD trial

Results of this small phase 2 trial were published in October 2017. Researchers found that clemastine improved the speed at which messages travelled from the eye to the brain - an early indication that clemastine can boost remyelination.

The treatment was associated with increased fatigue, but no severe adverse events were reported.

The trial involved 50 people with relapsing MS, and ran for five months. Researchers tested if 4 mg clemastine twice daily taken alongside a licensed disease modifying therapy (DMT) was better than taking the DMT alone. After three months, everyone involved in the trial took clemastine.

Phase 1 research

A small phase 1 trial completed in 2010 suggested that clemastine could suppress the immune response. The researchers found that the immune cells in 10 healthy volunteers injected with 2mg clemastine were less active than in volunteers given a placebo.

Clemastine has not been widely tested in people with MS so its side effects specifically for people with MS are not yet known. However, when used to treat allergy symptoms, side effects include drowsiness and fatigue, dizziness, and sometimes headaches, dry mouth, and nausea.

Clemastine has not been widely tested in people with MS so it isn’t yet known how it compares to existing MS treatments.

Clemastine is already licensed for other conditions but will need to undergo larger phase 2 and phase 3 trials to definitively test its effectiveness in MS. This process will take several years.