This is a a multi-center, randomized, double-blind, parallel group, and placebo controlled, two-arm study of a single oral dose of NXN-188 for the treatment of acute migraine headache without aura. Up to 120 migraineurs will be enrolled. Approximately 60 subjects having a headache history of migraine without aura will complete each of the two treatment arms to evaluate NXN-188 600 mg or placebo.