Ampyra (dalfampridine) is a new medicine to improve MS symptoms that was approved by the FDA in January 2010.
It should be marketed and available for use by March 2010.
Ampyra is a continuous release
formulation of 4-aminopyridine (4AP). 4AP has been around and used in MS for a long time, but well designed studies
demonstrating a measurable benefit in MS were only completed in the last few years.
One of the things
that happens with demyelination in MS is that nerve signals can't get through demyelinated areas. Depending on what
that nerve does, this can cause weakness, numbness, vision problems, and the other symptoms that occur in MS. Without
getting into the details, fampridine is supposed to improve the transmission of nerve signals through areas of damaged myelin,
and improve symptoms. It is a symptomatic treatment, i.e. it treats the symptoms of MS, but it does not modify
the course of MS by reducing number of relapses or accumulation of disability. Although symptomatic treatments
don't alter the course of disease, they can make a big difference in quality of life.
In my experience
with Ampyra and 4AP, the benefit in any person is hard to predict. Some people feel it makes a big difference in their
daily activities while other people don't notice any difference. This probably reflects the severity, type, and location
of the damage that MS has caused in the brain and spinal cord. 4AP would be expected to improve conduction across moderately
damaged areas, but not in areas with severe damage. In the clinical studies, about 30 to 40% of the subjects were considered
responders.
The FDA approved Ampyra because it had a measurable effect on walking speed. It probably
should also have benefits on other symptoms which are harder to measure, including sensory symptoms and fatigue.
The
most concerning side effect of Ampyra is seizures. The risk of seizures increases with higher doses of the drug, and
is reduced by a carefully controlled dose and the continuous release formulation. But some seizures occurred in patients
who were taking the drug as recommended.
