Dose effects of modafinil in sustaining wakefulness in narcolepsy patients with residual evening sleepiness.

Excessive sleepiness associated with narcolepsy lasts throughout the waking day. The authors conducted two randomized, double-blind studies to compare the efficacy of modafinil once-daily versus split doses in maintaining wakefulness throughout the day. Fifty-six patients received modafinil. The split-dose regimens were significantly more effective than the 200-mg once-daily regimen for sustaining wakefulness in the late afternoon/evening. All modafinil dosing regimens were well tolerated. In patients who experience excessive sleepiness in the late afternoon/evening, despite satisfactory treatment earlier in the day, a split dose of modafinil may promote wakefulness throughout the waking day.