Over-the-counter antihistamine found to repair damaged brain nerves could treat multiple sclerosis

Researchers are testing an over-the-counter antihistamine that could treat multiple sclerosis (MS) in a breakthrough that could help 2.5 million people worldwide.

Scientists from the University of California, San Francisco, found that MS patients treated with clemastine, used to relieve fever and allergy symptoms, had a slight increase in myelin water in the brain, which indicates myelin repair.

Dr Ari Green, medical director of the UCSF Multiple Sclerosis and Neuroinflammation Center and a Weill Institute for Neurosciences member, said: ‘This is the first example of brain repair being documented on MRI for a chronic neurological condition.

‘The study provides the first direct, biologically validated, imaging-based evidence of myelin repair induced by clemastine. This will set the standard for future research into remyelinating therapies.’

Almost one million people are living with MS in the US. It is a disease of the central nervous system where the flow of information between the brain and body is disrupted

With MS, patients lose myelin — the protective insulating layer around nerve fibers.

This leads to delays in nerve signals, which causes things such as weakness and spasticity, vision loss and cognitive slowing.

Water trapped between the thin layers of myelin in the brain cannot move as freely as water floating around brain cells.

Using an MRI scan, researchers measured the ratio of myelin water to the total water content in brain tissue to compare the difference in myelin levels before and after the drug was given to patients.

In the study, 50 patients with MS were divided into two groups.

The first group was given clemastine for the first three months of the study, and the second group was given it for months three to five.

The researchers found that myelin water increased in the first group after participants were given the antihistamine and continued to grow even after they stopped taking the drug.

In the second group, there were decreases in myelin water in the first part of the study under the placebo, but levels increased after they started taking clemastine.

In the most recent study, the researchers looked at the corpus callosum — the part of the brain which joins the right and left hemispheres and has a high myelin content.

They found that substantial repair happened outside the visible lesions commonly linked to MS.

Clemastine works in this instance by stimulating myelin-making stem cells.

Dr Green said: ‘Clemastine can only be partially effective at the doses we can use.

‘It can be sedating, which may be especially undesirable in patients with MS. We are hopeful better medications will be developed, but clemastine has proven to be the tool to show remyelination is possible.’

The study was published in the journal PNAS.

Almost one million people are living with MS in the US. It is a disease of the central nervous system where the flow of information between the brain and body is disrupted.

Clemastine is typically used to relieve hay fever and allergy symptoms. It works by blocking the action of histamine, a substance in the body that causes allergy symptoms.