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NEUROLOGY 1975;25:263
© 1975 American Academy of Neurology

Effect of chronic levodopa treatment on pyridoxine metabolism

HAROLD MARS, M.D., C.M., F.R.C.P.(C)

Division of Medicine, Department of Neurology, Mt. Sinai Hospital, Case Western Reserve University, Cleveland.

Pyridoxine metabolism was investigated in eight chronic levodopa-treated parkinsonian patients and in eight matched dopa-naive controls by measurement of plasma and erythrocyte pyridoxal-5-phosphate concentrations over a 24-hour period, following intravenous administration of pyridoxine. After both a 10 mg and 100 mg pyridoxine dosage, plasma and erythrocyte pyridoxal-5-phosphate concentrations were significantly higher in the chronic levodopa-treated group than in the controls. The percentage change in pyridoxal-5-phosphate concentrations as a function of the administered doses of pyridoxine was greater in the dopa-treated group. Chronic administration of levodopa may result in an adaptive alteration in the decarboxylase system with an increased cellular ability to synthesize pyridoxal-5-phosphate from pyridoxine, possibly through enzyme induction. This metabolic alteration would protect against pyridoxine deficiency states and may explain in part the progressive loss of levodopa effectiveness sometimes observed.

Presented in part at the twenty-sixth annual meeting of the American Academy of Neurology, San Francisco, April 1974.

Received for publication May 28, 1974.

Dr. Mars' address is Department of Neurology, University Hospitals, Case Western Reserve University, University Circle, Cleveland, OH 44106.






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