The effect of fampridine on the risk of seizure in patients with multiple sclerosis.

Background: Fampridine was first approved by the US Food and Drug Administration (FDA) to improve walking in multiple sclerosis (MS) patients, which was demonstrated by an increase in their walking speed. Nevertheless, the medication has been reported to possess an epileptogenic effect since it blocks the voltage-gated potassium channels in neural fibers. Several studies have indicated that the risk of seizure among fampridine consumers is not substantially higher than that in the general MS population, however. The objective of this study is to describe 97 MS patients for whom fampridine was prescribed and to assess the incidence of post-medication seizures.

Methods: This cohort study included 97 MS patients with gait problems who referred to the Isfahan Clinic of MS from August 2017 to September 2019. The exclusion criteria were a previous or family history of seizure or a history of renal impairment. Fampridine was prescribed for all the patients at a dose of 10 mg twice daily (12 hours apart).

Results: three patients (with an approximate incidence rate of 0.015 per 100 patient-years) presented with generalized tonic-clonic seizures, 7, 9, and 14 months after initiating fampridine consumption. The radiological findings revealed significant cortical and subcortical lesions in the three patients. Further, two of them consumed baclofen or fingolimod simultaneously with fampridine.

Conclusion: The reported incidence rate is relatively higher than that in the general MS population. The extensive (sub) cortical lesions and the concomitant medications probably have an important role in the epileptogenesis, regardless of fampridine. However, the potential pro-convulsant properties of fampridine should not be overlooked.