Trait Interindividual Differences in the Effectiveness of Modafinil.

Purpose: To optimize the usage of modafinil as a cognitive enhancer and increase safety and effectiveness, we sought to assess the trait-characteristic of modafinil-sensitivity. Methods: 11 healthy participants (age = 21 ± 2 yr) were tested on 2 separate occasions during which they were sleep deprived for one night. During one trial they received 2 × 200 mg modafinil (i.e. EXP); during the other they received 2 × a placebo-capsule (i.e. CON). Physiological (e.g. heart rate and blood pres-sure), subjective (e.g. sleepiness and mood state) and behavioral (e.g. psychomotor vigilance task) measures of sleep-wake regulation were followed up. Results: Both PVT performance and perceived sleepiness were significantly improved in EXP at 2AM and 4AM during the sleep deprivation-night, compared to in CON. Additionally, an ICC of 0.90 for the delta (CON – EXP) in non-adjusted reaction time was observed. Conclusion: Stable and robust interindividual differences in modafinil-sensitivity are clearly present across day and night.