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So that reinforcing and subjective effects of methylphenidate as a function of dose and level of sleepiness could be evaluated, 21 volunteers received methylphenidate (5, 10, or 20 mg) or placebo on 2 sampling days. After 4 and 8 hr time in bed (TIB), they chose their preferred capsule on 5 days. Methylphenidate was chosen more frequently after 4 hr TIB (60%) than it was after 8 hr TIB (33%). The strongest preference (68%) was seen in the 10-mg group. At 10 and 20 mg, stimulant-like subjective effects were reported. The 10-mg group was more adversely affected by the restricted bedtime and showed more pronounced drug effects with methylphenidate. These results indicate that sleepiness modulates the reinforcing and subjective effects of methylphenidate.

The purpose of this study was to characterize the level of sleepiness/alertness following the nocturnal administration of dexamethasone. Thirteen healthy men participated in this study. Following the initial screening, dexamethasone (4 mg) or placebo was administered at 22:30 hr in a randomized double-blind procedure. Subjects were given nap opportunities at 23:00, 1:00, 3:00, 4:30, 5:30, 7:30, 9:30, 11:30, 13:30, 15:30, 17:30, and 19:30 hr. The administration of dexamethasone resulted in an overall lengthening of sleep latency. Although the two groups displayed comparable latencies to stage 1 for the 23:00-7:30 hr nap opportunities, the administration of dexamethasone resulted in significantly longer latencies on the 9:30-19:30 hr nap opportunities. Consistent with these results, participants reported significantly greater levels of alertness on the Stanford Sleepiness Scale. The results of this study revealed greater levels of daytime alertness following the nocturnal administration of dexamethasone.

Are symptoms of daytime sleepiness relevant among patients with insomnia? Patients with insomnia frequently report daytime consequences secondary to their difficulty initiating and maintaining sleep. The purpose of this study was to determine the frequency of daytime sleepiness as defined by a self-reported measure of daytime sleepiness (the Epworth Sleepiness Scale). In addition, the study characterized the patients' psychological status using the Symptom Checklist-90-Revised. The study corroborated a relatively high frequency of excessive daytime sleepiness and psychiatric conditions among patients with insomnia. Furthermore, the results of the study suggest variation in psychological distress levels, according to the different levels of sleepiness/alertness.

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