Clinical Reminders |
Disequilibrium due to a vitamin B6 megadose supplement
1 Medway Maritime NHS Trust, Kent, Elderly Care, Windmill Road, Gillingham ME7 5NY, UK
2 Neurophysiology, King's College Hospital, London SE5 9RS, WA
3 Department of Clinical Gerontology, King's College Hospital, London SE5 9RS, UK
* To whom correspondence should be addressed Email: joscyn{at}hotmail.com
An 80-year-old woman was referred by her GP with worsening disequilibrium over the previous 18 months.
Medications included a megadose vitamin B6 preparation (reportedly approximately 200 mg per week).
Examination revealed signs of a dorsal column sensory neuropathy.
Appropriate investigation revealed no other cause for dorsal column sensory loss.
Symptoms and signs improved completely on cessation of the supplement after a period of weeks.
Dorsal column toxicity due to pyridoxine has been described since the 1980s [1–3]. In the series (n = 24, age range 20–53 years), the daily dose of B6 varied from 200 mg to 6 g. Only one serum level was reported as ‘in excess of 30 ng/ml’ (120 nmol/l) [1] which accords with the level (171 nmol/l) demonstrated in this case. A recent case report from the Netherlands suggested a toxic effect of B6 at a daily dose of 24–40 mg in two men in their seventh decade [4]. A similar dose to that is described here.
A safe dose of 150–200 mg daily is suggested by the experience of one US centre [5] albeit in a younger cohort of 70 individuals. The US no-observed-adverse-effect level is set at 200 mg, safe upper limit at 100 mg and recommended daily amount (RDA) 2 mg [6].
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References |
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 Top References |
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- Schaumberg H, Kaplan J, Windebank A, et al. Sensory neuropathy from pyridoxine abuse: a new megavitamin syndrome. N Engl J Med (1983) 309:445–8.[Abstract]
- Parry G, Bredesen D. Sensory neuropathy with low-dose pyridoxine. Neurology (1985) 35:1466–8.
[Abstract/Free Full Text] - Berger A, Schaumberg H. More on neuropathy from pyridoxine abuse [letter]. N Engl J Med (1984) 311:986–7.[Web of Science][Medline]
- de Kruijk J, Notermans N. Sensory disturbances caused by multivitamin preparations. Ned Tijdschr Geneeskd (2005) 149:2541–4.[Medline]
- Bernstein A. Vitamin B6 in Clinical neurology. Ann N Y Acad Sci (1990) 585:250–60.[Web of Science][Medline]
- Katan M. How much vitamin B6 is toxic? Ned Tijdschr Geneeskd (2005) 149:2545–6.[Medline]
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