 Fastin was once a brand name of a drug called phentermine and the Fastin brand of phentermine was manufactured by King Pharmaceuticals.Fastin and 10 other products manufactured by Hi Tech Pharmaceuticals were banned by the U.S. Food and Drug Administration (FDA) in 2013 because they contain Dimethylamylamine HCl (DMAA), an illegal food additive that is deemed unsafe.At the request of the FDA, U.S.