Medicines in MS can essentially be divided into two different categories:
- those that prevent relapses and progression of the disease (called disease-modifying drugs)
- medications used to treat the symptoms of MS
Within the past year and a half, two pills were approved by the FDA specifically for MS for the first time. One medication is fingolimod (Gilenya®), a disease-modifying drug. The other is dalfampridine (Ampyra ®), which was approved in January 2010. This medication was investigated specifically to improve walking speed in patients with MS. Clearly, walking difficulties are some of the most common and disabling symptoms of MS.
Ampyra works by blocking potassium channels in axons, thereby improving nerve conduction in areas of the brain and spinal cord that have been damaged in MS. It is a 10mg pill that is taken twice daily. Although the FDA approval is relatively new, the medication itself is not. Dalfampridine was previously available through compounding pharmacies in the US. Previously it was called simply fampridine or 4-aminopyridine (4AP).
As with any medicine, the news about Ampyra can be divided into the good and the bad.
The good news about Ampyra:
- It works. Patients with MS who took Ampyra had improvement in their walking speed (as measured on a 25-foot walk) four times as often as those who took placebo. Responders to Ampyra were defined as patients whose walking speed was faster on at least three of four on-treatment visits than their fastest speed at any of five off-treatment visits. Those patients who did have an improvement, improved by nearly 25 percent.
- It is generally very safe. No serious adverse effects were noted in the patients who took Ampyra compared to those who took placebo. At higher doses than the 10mg twice daily (studied in other trials), the medication has been associated with seizures. The medication should therefore not be used in any patient who has a history of seizures or who has kidney disease that might allow the medicine to build up to toxic levels and lead to a seizure. In the clinical trials, subjects who took the medicine reported more symptoms consistent with a urinary tract infection compared to those who received placebo.
The bad news about Ampyra:
- It does not work for everybody. In the two main clinical trials, only about 40 percent of the patients were considered responders, meaning that 60 percent of patients did not respond to the medicine. And the improvement that the responders did notice was relatively modest, in my opinion.
So what does this mean, practically, for patients with MS? Certainly, it is wonderful to have any new medicine available for patients with MS, especially a pill, especially a safe pill, and especially a pill that could help with potentially disabling symptoms of MS. However, I tell my patients starting the medication, that while it certainly may help them, it is unlikely to be a miracle. And while a few of my patients have reported significant improvement in their walking, my clinical experience is similar to that of the trials: most patients do not feel significantly different on the medication.
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