Unisom is the Chattem bran name for an over-the-counter sleep-aid medication. While marketed under a single trademark, the active ingredient may be one of two drugs, depending on the type of preparation. Doxylamine succinate is sold in 25 mg dosages as tablets, and diphenhydramine hydrochloride is sold as tablets, and also in liquid/gelatin preparation in dosages of 50 mg.