Provigil (modafinil) 200 mg is a prescription medication used to promote wakefulness in adults with narcolepsy, obstructive sleep apnea, or shift work sleep disorder. The standard dosage is 200 mg taken orally once daily, typically in the morning for narcolepsy or sleep apnea, or one hour before a work shift for shift work disorder; doses up to 400 mg/day may be tolerated but offer no proven extra benefit. Purchasing Provigil 200 mg online requires a valid prescription from a licensed healthcare provider.