Abstract
During the past several decades, there have been numerous reports on the efficacy of pyridoxine (vitamin B6) in the treatment of a wide range of clinical conditions. Gaby has hypothesized that the proliferation of environmental pollutants and food additives that are known or suspected to interfere with vitamin B6 metabolism has created a new epidemic of vitamin B6 deficiency and greatly broadened the spectrum of pyridoxine-responsive disorders [1]. In addition to its classical indications, such as pyridoxine-responsive anemia and certain inborn errors of vitamin B6 metabolism, pyridoxine is now being prescribed by some practitioners for patients with cardiovascular disease, diabetes mellitus, premenstrual syndrome, toxemia of pregnancy, carpal tunnel syndrome, urolithiasis, sickle cell disease, certain types of depression and arthritis, attention deficit disorder and asthma.
Until recently, pyridoxine was considered perfectly safe, even in extremely large doses. Consequently, there was little concern that some individuals were taking, either by prescription or by self-medication, amounts many hundreds of times greater than the Recommended Dietary Allowance. However, reports of neurotoxocity in persons ingesting megadoses of this vitamin necessitated a re-evaluation of its safety.
Some observers have over-reacted, concluding that pyridoxine is a dangerous vitamin that should never be used for ‘unproven’ indications; others have recognized that anything can be toxic in large enough doses. Given its clinical value, pyridoxine therapy should not be abandoned, merely because there is some risk in huge doses. The purpose of this paper is to review the literature on pyridoxine neurotoxicity, as well as other less serious potential side effects.
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