“Seizures are a well know side effect of the aminopyrdines (the active ingredient in fampridine). Fampridine works by making nerve cells more likely to discharge an electrical impulse. This is how they increase the walking speed of MSers.”
“The great Professor W. Ian MacDonald, who was my mentor, was one of the first neurologists to use 4-aminopyridine in MS. The first MSer he treated with the drug as part of a clinical trial had a seizure. Needless to say he stopped the trial. Fampridine, is a slow release form of 4-aminopyridine, that has been designed to prevent high peak levels of the drug, which are associated with seizures. Nevertheless some MSers will still have seizures on the drug.”

How frustrating; what MSers have to contend with, it really is a bit of a b**r!
Some MSers are prone to seizures, and may have had symptoms of seizure before starting on Fampridine. It seems that these unfortunate few suffer early on when they start with Fampridine. After the first month, those who have not have a seizure are more likely to continue safely.I have had a very positive benefit from Fampridine,and being able to walk (fairly)easily again, having much better energy levels, and better bladder control make me feel this is the best MS treatment I have been on. Well worth any potential ill effects.