The effectiveness of modafinil in improving wakefulness in adult patients with excessive sleepiness associated with narcolepsy was established in two US 9-week, multi-center, placebo-controlled, parallel-group, double-blind studies of outpatients who met the criteria for narcolepsy. A total of 558 patients were randomized to receive modafinil 200 or 400 mg/day, or placebo. The criteria for narcolepsy include either: 1) recurrent daytime naps or lapses into sleep that occur almost daily for at least three months, plus sudden bilateral loss of postural muscle tone in association with intense emotion (cataplexy); or 2) a complaint of excessive sleepiness or sudden muscle weakness with associated features: sleep paralysis, hypnagogic hallucinations, automatic behaviors, disrupted major sleep episode; and polysomnography demonstrating one of the following: sleep latency less than 10 minutes or rapid eye movement (REM) sleep latency less than 20 minutes. For entry into these studies, all patients were required to have objectively documented excessive daytime sleepiness, via a Multiple Sleep Latency Test (MSLT) with two or more sleep onset REM periods and the absence of any other clinically significant active medical or psychiatric disorder. The MSLT, an objective polysomnographic assessment of the patient’s ability to fall asleep in an unstimulating environment, measured latency (in minutes) to sleep onset averaged over 4 test sessions at 2-hour intervals. For each test session, the subject was told to lie quietly and attempt to sleep. Each test session was terminated after 20 minutes if no sleep occurred or 15 minutes after sleep onset. 

In both studies, the primary measures of effectiveness were: 1) sleep latency, as assessed by the Maintenance of Wakefulness Test (MWT); and 2) the change in the patient’s overall disease status, as measured by the Clinical Global Impression of Change (CGI-C). For a successful trial, both measures had to show statistically significant improvement.

The MWT measures latency (in minutes) to sleep onset averaged over 4 test sessions at 2 hour intervals following nocturnal polysomnography. For each test session, the subject was asked to attempt to remain awake without using extraordinary measures. Each test session was terminated after 20 minutes if no sleep occurred or 10 minutes after sleep onset. The CGI-C is a 7-point scale, centered at No Change, and ranging from Very Much Worse to Very Much Improved. Patients were rated by evaluators who had no access to any data about the patients other than a measure of their baseline severity. Evaluators were not given any specific guidance about the criteria they were to apply when rating patients. 

Both studies demonstrated improvement in objective and subjective measures of excessive daytime sleepiness for both the 200 mg and 400 mg doses compared to placebo. Patients treated with modafinil showed a statistically significantly enhanced ability to remain awake on the MWT at each dose compared to placebo at final visit (Table 2). A statistically significantly greater number of patients treated with modafinil at each dose showed improvement in overall clinical condition as rated by the CGI-C scale at final visit (Table 3).

Nighttime sleep measured with polysomnography was not affected by the use of modafinil.