The results of a new study suggest that an investigational drug called fampridine is a safe treatment that may enhance walking ability in some patients with multiple sclerosis.

Multiple sclerosis is a disease of the nervous system caused by damage to the sheaths that protect nerve cells. It affects 2.5 million people globally and can cause mild illness in some people and permanent disability in others. Symptoms may include numbness or weakness in the limbs, loss of vision and an unsteady gait.

The functional improvement seen with fampridine "was associated with a reduction of patients' reported (walking) disability, and is a clinically meaningful therapeutic benefit," Dr. Andrew D. Goodman, from the University of Rochester Medical Center, New York, and colleagues conclude.

The study, reported in The Lancet, featured 301 patients with any form of multiple sclerosis who were randomly assigned to receive fampridine or inactive "placebo" daily for 14 weeks. The main focus of the study was on the time it took patients to walk 25 feet.

Thirty-five percent of fampridine patients walked faster after receiving the drug than they did before treatment. By contrast, just 8 percent of subjects in the comparison group showed an improved walking time with placebo.

Moreover, among responders, the average improvement in walking speed was greater with fampridine than with placebo: 25.2 versus 4.7 percent.

Eight possible treatment-related side effects were seen with fampridine. Two serious effects, seizure and severe anxiety, were thought to be related to the drug, although prior research has suggested that these problems may be addressed by reducing the dose.