Efficacy of modafinil and caffeine to counteract hypnotic induced sleepiness during sustained operations

Introduction: During sustained operations, a combined use of a hypnotic to induce sleep under difficult circumstances and a psychostimulant to improve performance and alertness during night-shift work or after sleep deprivation may be necessary. This study was conducted to evaluate the effect of modafinil and caffeine as countermeasures to hypnotic induced sleepiness.
Methods: 18 healthy subjects (moderate coffee consumers) participated in a randomized placebocontrolled double-blind crossover study. Sleepiness was induced by limited sleep deprivation combined with the administration of 20 mg temazepam (rapidly absorbed formulation). 200 mg modafinil or 400 mg caffeine or placebo were administrated in a cross-over design, one hour after administration of temazepam. Subjects completed performance and alertness tests before administration of temazepam (baseline), once after administration of temazepam and at regular intervals during the night until eight hours after administration of modafinil, caffeine or placebo. Vigilance, alertness, complex information processing and subjective sleepiness were assessed.
Results: After temazepam intake, performance and alertness were significantly impaired. Compared with placebo, both caffeine and modafinil significantly counteracted the performance and alertness impairment caused by temazepam. The greatest impact of the psychostimulants was seen in performance on the vigilance task. The onset of beneficial action was shortest with caffeine (1½ hr), modafinil showed a significant counteraction to temazepam starting 4½ hours after administration. Both stimulants showed a beneficial effect in the vigilance task as long as eight hours after administration. No significant adverse effects were observed.
Conclusion: Both caffeine and modafinil are useful to counteract the sedative effects of temazepam. The onset of caffeine is earlier than the onset of modafinil. Therefore, in this study the mean performance enhancing effects of 400 mg caffeine were better in counteracting the hypnotic induced sleepiness of temazepam than the effects of 200 mg modafinil.