In a study published in The Lancet Neurology, researchers found that an anti-seizure drug called phenytoin protected against nerve damage in people with optic neuritis.

Optic neuritis is a common symptom of MS, in which the optic nerve that carries visual information from the eye to the brain becomes inflamed and damaged. For some people, optic neuritis can be the first sign of MS.

Study leader Dr. Raj Kapoor, of the Institute of Neurology at University College London in the UK, and his team focused on patients with optic neuritis because inflammation and damage to eye nerves are simple to measure.

Specifically, the researchers set out to determine whether phenytoin could block sodium from entering axons in nerve cells; excess sodium in nerve cells leads to an overproduction of calcium, which causes nerve damage.

“We wanted to find out if the theory that blocking sodium currents, which we developed in basic work over many years, actually served to protect neural tissue – a test-bed to see if we can achieve neuroprotection,” explains Dr. Kapoor.

30% less nerve damage with phenytoin

The team enrolled 86 individuals aged 18-60 with optic neuritis. The participants were randomized to receive either 4 mg/kg or 6 mg/kg of phenytoin or a placebo each day for 3 months.

At the end of the 3 months, all participants underwent optical coherence tomography (OCT), which measured the thickness of the retinal nerve fiber layer (RNFL) at the back of the eye.
Compared with participants who took the placebo, those who took phenytoin had around.

 

30% less damage to the RNFL.

Dr. Kapoor hails these findings as “promising,” noting that not only could phenytoin open the door to a new treatment for optical neuritis, but it could also lead to a new treatment for all nerve damage caused by MS.