Modafinil 200mg tablet is a prescription medication used to improve wakefulness in adults who experience excessive sleepiness due to narcolepsy, obstructive sleep apnea, or shift work sleep disorder. It works by increasing the levels of certain chemicals in the brain that control the sleep/wake cycle. The tablet is typically taken once daily in the morning or as directed by a healthcare provider. It should not be used as a substitute for getting enough sleep or treating other underlying sleep disorders. Side effects may include headache, nausea, nervousness, and difficulty sleeping.