Effect of 4-aminopyridine on vision in multiple sclerosis patients with optic neuropathy

The objective of this randomized, double-blind, placebo-controlled, crossover study was to examine if patients with optic neuropathy would derive a therapeutic benefit from 4-aminopyridine (4-AP) treatment. Furthermore, the study was intended to determine if patients with certain P100 latencies or retinal nerve fiber layer (RNFL) measures would be more likely to respond to therapy.

Patients were enrolled in a randomized, placebo-controlled, double-blind, crossover study of 10 weeks duration. Patients underwent visual evoked potentials (VEP), optical coherence tomography (OCT), and visual acuity before starting 5 weeks of either placebo or 4-AP. After 5 weeks, they completed a second evaluation (VEP, OCT, and visual acuity) and were crossed over between treatment arms. Five weeks later, they had their final evaluation. All investigators were blinded to treatment arm until after data analysis.

On average, patients had faster P100s on 4-AP when compared to placebo. A subset of patients had distinct responses to 4-AP as measured by improvements in visual acuity. Finally, eyes with an RNFL measure between 60 and 80 µm had the highest response rate.

4-Aminopyridine is useful for improving vision in patients with demyelinating optic neuropathy. Future clinical trials may be able to enrich a patient population for potential responders using OCT and VEP measures. Selecting patients for future trials should use RNFL measures as part of inclusion/exclusion criteria.

This study provides Class IV evidence supporting the use of 4-AP in certain patients with optic neuropathy to improve visual function (patients with RNFL between 60 and 80 µm).