Pantethine (bis-pantethine or co-enzyme pantethine) is a imeric form of pantothenic acid (vitamin B5). It is composed of two molecules of pantothenic acid linked by cysteamine bridging groups. The monomer of this compound is known as pantetheine and is an intermediate in the production of Coenzyme A by the body. Pantethine is considered the more biologically active form of vitamin B5, but it is less stable, decomposing over time if it is not kept refrigerated. Most vitamin B5 supplements are therefore in the form of calcium pantothenate, a salt of pantothenic acid.