Pantothenic acid (vitamin B5) is a water-soluble B-complex vitamin that was identified in 1933, isolated and extracted from liver in 1938, and first synthesized in 1940.1 R. J. Williams is credited with coining the name from the Greek word panthos, which translates as “from everywhere.” It was given this name because of its widespread presence in food.2 Most vitamin B5, and its derivatives or precursors, added to foods and beverages, or used in dietary supplements, is made by chemical synthesis.2,3 Only the Dextrorotatory (D) isomer of pantothenic acid – D-pantothenic acid – possesses biologic activity. Pure D-pantothenic acid can be used as a dietary supplement: it is water-soluble, viscous, and yellow in color. Because D-pantothenic acid is relatively unstable – it can be destroyed by heat and acid and alkaline conditions – the more stable calcium pantothenate is the form of vitamin B5 usually found in dietary supplements. It is water-soluble, crystalline, and white in color. Ten mg of calcium pantothenate is approximately equivalent to 9.2 mg of pure D-pantothenic acid.2 [Note: A monograph on pantethine was published in volume 15 of Alternative Medicine Review in 2010.5] The disulphide form of pantothenic acid – pantethine – is also available as a dietary supplement. This is considered to be the most active form of vitamin B5 because it contains the sulfhydryl-group needed for biological activity in Coenzyme A (CoA).4 A liquid form of vitamin B5 – dexpanthenol, D-pantothenyl alcohol, D-panthenol, or panthenol – is also available. This is an alcohol provitamin of vitamin B5 (i.e., it is converted into pantothenic acid in the body), which is used primarily as a topical or injected form for cosmetic purposes or wound healing.6 Unless otherwise specified, the supplemental form of vitamin B5 used in studies referenced in this monograph is calcium pantothenate.