Modafinil is a typical drug that is used to treat sleep-related problems such as narcolepsy, work- related sleep disorders, or excessive sleepiness in the morning. This drug is also commonly used for problems associated with obstructive sleep apnea. Dose: 100 – 200mg Half-life: 15 hours Majority of the drug's users — such as students who take it to study for exams — use it off-label, as a smart drug to improve focus.