Ibuprofen, a non-steroidal anti-inflammatory drug, is not sold in the United States in 500 milligram doses. It is available by prescription in 400, 600 and 800 milligram tablets for oral administration, according to a U.S. Food and Drug Administration docket. Non-prescription ibuprofen is available in 100 and 200 milligram tablets.
Non-prescription ibuprofen is sold over the counter in generic versions and brand names such as Motrin and Advil. Ibuprofen is often taken to reduce fever and treat headaches, toothache, arthritis, menstrual cramps, back pain or minor injuries. By prescription, the maximum adult dose of ibuprofen is 800 milligrams per single dose or 3,200 milligrams per day. The limit of over-the-counter ibuprofen is less, with a maximum daily dose of 1200 milligrams, explains About.com.