How long does Provigil last?

My sleep doc gave me a sample of 200 mg Provigil tabs. I usually only get sleepy early afternoon. Does anyone take Provigil and know how long the effects last?
Mary Z. Thanks.

I think the half life is around 15 hours. If you take it late in the day, or if you're not used to that dose, you may have trouble sleeping. I take it very early in the morning....if I get up late on weekends, I just don't take it, bc I will be up all night.

I take 400 mg per day.

Thanks, just what I needed to know.

Duration of action is very idiosyncratic (says the mother of a 7-year old who metabolizes a 12-hour stimulant in 5 hours...). Provigil lasts me about 3-4 hours, max. There's a difference between the behavioral effects of a medication vs. duration of the side effects, so I still don't take it after 1pm even though I really don't feel its effects anywhere even approaching bedtime.

I think it also depends on the night before. Sleep quality, health (sick),... I take 200mg/day and like the others, I don't take it after 8 am. My doctor switched me to Nuvigil 250mg/day but I felt like the Provigil works better for me. Hope this helps.