A modafinil daily dosing strategy promotes wakefulness in narcolepsy patients experiencing excessive daytime sleepiness; however, some patients may continue to experience late-day sleepiness. Excessive sleepiness in narcolepsy is associated with cognitive impairment. Modafinil has improved executive function in other models of excessive sleepiness. This study evaluated the effects of once-daily vs. split doses of modafinil on wakefulness and of combined doses on executive function in narcolepsy patients experiencing late-day sleepiness despite satisfactory modafinil treatment earlier in the day.
After a 2-week washout, 24 patients received 3 weeks of double-blind treatment with modafinil 400-mg once daily (7 AM) plus placebo (noon) or modafinil 600-mg split dose (400 mg, 7 AM; 200 mg, noon). Assessments included a Maintenance of Wakefulness Test (MWT) for individual regimens and the Wisconsin Card Sort Test (WCST) for treatments combined.
Modafinil 600-mg split dose was significantly more effective than modafinil 400-mg once daily in improving late-day MWT scores (5 PM–7 PM; P < 0.05). Significant mean (± SEM) reductions from baseline of 8.2 ± 2.7 in the total number of errors and 5.9 ± 1.9 in total percent of errors (P < 0.05, both) were demonstrated for modafinil on the WCST. Modafinil was well tolerated; adverse events included headache (n = 1), emotional lability (n = 1), bronchitis (n = 1), and accidental injury (n = 2), with no reports of insomnia.
For patients with residual late-day sleepiness associated with narcolepsy, an additional 200-mg dose of modafinil taken at midday was effective in sustaining wakefulness throughout the entire waking day. Treatment with modafinil also significantly improved executive function.