[Peripheral sensory neuropathy produced by a megadose of vitamin B6]

Clinical cases of sensory neuropathy produced by a megadose of vitamin B6 have been reported in English literatures. We investigated the ordinary daily dosage and maximal dose of vitamin B6 widely adopted in Japan, and the amount of vitamin B6 per unit (per tablet, capsule or ampule) available in our medical practice. We concluded that in Japan it is very rare to administer such a large dose of vitamin B6 that produced sensory neuropathy described in the literatures. In our experimental study, Sprague-Dawley rats were intraperitoneally given a total amount of 14,000 mg/kg of body weight of pyridoxine hydrochloride in ten separate doses. They developed an ataxic gait. The occurrence of the degeneration of nerve cell bodies and peripheral axons of lumbar primary sensory neurons were histologically demonstrated. Although in Japan no clinical cases of neuropathy produced by a megadose of vitamin B6 have been reported to our knowledge, it is necessary to be aware of the possible occurrence of such neuropathy among patients with polyneuropathy of unknown etiology or who have been receiving vitamin B6 for a long time.