Pharmacological use of L-carnitine in uremic anemia: has its full potential been exploited?

Anemia is one of the most frequent complications of kidney failure and a common cause of morbidity in dialysis patients. A number of clinical studies have suggested that l-carnitine (LC), a naturally occurring compound involved in bioenergetic processes, may alleviate the anemia of hemodialysis patients. Since LC deficiency is commonly present in dialysis patients, LC has been described as a "conditional vitamin". However, the use of LC supplementation in dialysis remains controversial as well as its mode of action in preventing anemia. Recent literature shows that to fully exploit its pharmacological potential, LC may have to be administered at doses that achieve supra-physiological levels of LC in plasma and target organs. However, this concept has not been fully investigated in uremic patients. In this article, we will review the use of LC in dialysis patients, and provide a rationale for the anti-anemic action of LC based on biophysical, metabolic and antiapoptotic effects of this compound on erythropoiesis and the function of mature, circulating erythrocytes. The discussion will be focused on experimental and clinical data that support the concept that supra-physiological concentrations of LC may improve the anemic condition of dialysis patients, as would be expected from a "conditional drug" rather than a "conditional vitamin".