Failure of vitamin B6 to reverse the L-dopa effect in patients on a dopa decarboxylase inhibitor

Abstract

Seven patients with Parkinsonism previously on l-dopa were placed on a regimen of l-dopa and alpha methyl dopa hydrazine (a dopa decarboxylase inhibitor). Two of these patients had previously shown marked clinical deterioration of the l-dopa improvement when given pyridoxine. None of the seven patients receiving alpha methyl dopa hydrazine demonstrated any change in their condition when given pyridoxine. The failure of vitamin B₆ to reverse the clinical effect of l-dopa in patients receiving both l-dopa and a peripheral dopa decarboxylase inhibitor suggests that reversal of the l-dopa effect induced by vitamin B₆ is due to increasing the activity of the enzyme dopa decarboxylase outside the central nervous system.