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

In this randomised, placebo-controlled, double-blinded study, the researchers examined if patients with optic neuropathy would benefit from 4-aminopyridine (4-AP) treatment and if patients with certain P100 latencies or retinal nerve fibre layer (RNFL) measures would be more likely to respond to therapy.

4-AP acts as a potassium channel blocker, which increases the fidelity of axonal excitability and augments conduction along demyelinated neurons. Patients underwent visual evoked potentials (VEP), optical coherence tomography (OCT) and visual acuity (VA) before starting five weeks of either placebo or 4-AP. After five weeks, they completed a second evaluation (VEP, OCT and VA) and were crossed over between the treatment arms. At week ten, they had their final evaluation.

The researchers found that on average, patients had faster P100s on 4-AP when compared to placebo. Eyes with an RNFL measure between 60 and 80µm had the highest response rate. This study demonstrates that 4-AP is useful for improving vision in patients with demyelinating optic neuropathy. The researchers suggest that clinical trials in the future use OCT and VEP measures for looking at potential responders and use RNFL measures as a part of inclusion/exclusion criteria.

Authors: Horton L, Conger A

Source: Neurology. 2013 Apr 24. [Epub ahead of print]

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