Abstract
Although cyanocobalamin and hydroxocobalamin are the most commonly encountered supplemental forms of vitamin B12, adenosyland methylcobalamin are the primary forms of vitamin B12 in the human body, and are the metabolically active forms required for B12-dependent enzyme function. Evidence indicates these coenzyme forms of vitamin B12, in addition to having a theoretical advantage over other forms of B12, actually do have metabolic and therapeutic applications not shared by the other forms of vitamin B12. This article will provide an overview of the metabolism and function of adenosyland methylcobalamin, and will discuss the potential therapeutic relevance of the coenzyme forms of vitamin B12 in a variety of clinical conditions, including anemia, anorexia, cancer, HIV, and liver and sleep disorders. (Alt Med Rev 1997;2(5):459-471)