At the same time, Black was trying to find a treatment for stomach ulcers. ICI did not wish to do this so Black stopped working for them in 1964. He joined Smith, Kline and French. He worked for them for nine years until 1973. While there, Black developed his second major drug, cimetidine. It was first sold under the brand name Tagamet in 1975. Tagamet soon outsold propranolol to become the world's largest-selling prescription drug.