Objective To investigate the effects of modafinil,a new wake-promoting agent, on vestibular function during 24 h sleep deprivation(SD). Method Eight male healthy young volunteers were exposed to two 24 h periods of continuous wakefulness during the crossover experiment. In one period, 200 mg doses of modafinil were given and in the other, separated by one week, matching placebos were administered. The SD time started from 8:00 of the first day to 8:00 of the second day. Drugs was given at 0:00 of the second day. Vestibular function was tested at 21:00 of the first day and 1 ,3,5,7 h after drug administration. Result The accuracy of saccade tracking and the gains of VVOR(visual-vestibular optokinetic reflex)and OKN(optokinetic nystagmus)in the placebo group decreased during 24 h SD, especially at 1: 00～5:00 of the second day, while OKN gains in the modafinil group was increased significantly. There were no significant differences of other vestibular function between modafinil group and placebo group. Conclusion Twenty four SD can influence vestibular function in certain degree,but optokinetic nystagmus can be improved by modafinil.

Objective To investigate the effects of modafinil,a new wake-promoting agent,on simulated flight performance during 48 h sleep deprivation(SD).Method Six male healthy young volunteers were exposed to two periods of 48 h continuous wakefulness during the crossover experiment.In one period,three 200 mg doses of modafinil were given and in the other,separated by two weeks,matching placebos were administered.The SD time started from 8:00 of the first day to 8:00 of the third day.Drug was given at 0:00,16:00 of the second day and 0:00 of the third day.Flight performance in J7-E flight simulator was tested at 21:00 of the first day and 1,3,5,7 h after each drug administration.Result The scores of simulated flight performance in the placebo group decreased with time during SD and became significant at 1:00～7:00 of the third day.Numbers of errors increased with time during SD,especially in the left ascending turn stage and the descending & landing stages.Compared with the placebo,flight performance was significantly increased after the third administration of modafinil.Numbers of errors during 48 h SD and at 1:00～7:00 of the third day in modafinil group was 19% and 40% lower than those in placebo group respectively.Conclusion Simulated flight performance during 48 h SD is significantly improved after repeated administration of modafinil,especially when the impacts of SD and the circadian trough are combined.