Buy Adderall 20 mg Online, Adderall 20 mg is a drug used to treat wakefulness disorders like narcolepsy, shift work sleep disorder and daytime sleepiness caused by obstructive sleep apnea. In the United States, it has been approved by the FDA in 1998 under the brand name Adderall XR . Adderall is usually prescribed at 10mg to be taken once a day but could range from 100 to 400 mg per day to be taken in a single dose or cut in half to make two doses.