Phenytoin Preserves Axons in Acute Optic Neuritis

Blockage of sodium channels has been suggested to be neuroprotective in animal models. Investigators conducted a double-blind phase II trial of phenytoin, a commonly available sodium channel blocker. They randomized 86 patients with acute optic neuritis within 2 weeks after onset to oral phenytoin (4–6 mg/kg/day) or placebo for 3 months. Follow-up was complete in 81 participants.

At 6 months, mean retinal nerve fiber layer thickness in the affected eye was 81.46 µm with phenytoin versus 74.29 µm with placebo. Macular volume was also improved with phenytoin. Optic nerve cross-sectional area on magnetic resonance imaging showed a trend for improvement (P=0.06). No difference was found for visual acuity, contrast sensitivity, visual evoked pote…