A few studies have been performed to check which way of taking Provigil is efficient – take it once a day, 1 tablet in a morning or in the beginning of each shift, or take it during the day in small portions? The studies performed were random, blind studies with a control placebo group.
The main reason to perform that study was a fact that Provigil usually works best in the first two hours of taking it, but the sleepiness effect of narcolepsy lasts a day.
The study had shown, that taking small portions of Provigil is more efficient than taking 1 portion a day, because it also helps people to stay awake during evening time.
You need to chose with your doctor which regime is better for you, as both of them are quite well tolerated.