The average duration of modafinil is 10 to 15 hours; individual differences may occur. Most people start feeling alert 30 to 60 minutes after taking a dosage such as modvigil 200 , and the effects peak in 2 to 4 hours. The wakefulness effect does not abruptly end; rather, it progressively diminishes. Duration is influenced by a number of factors, including age, metabolism, dose, sleep debt, and stimulant sensitivity. Modafinil is often used in the morning to prevent sleeplessness because it lasts most of the day. Although it increases alertness, it shouldn't be taken in place of sleep and should only be used under medical supervision.