Impairment of pyridoxal phosphate dependent metabolic reactions in a child with subacute necrotizing encephalopathy.

Ebadi, Manuchair; Bostad, R; Pellegrino, R.

doi:10.1136/jnnp.32.5.393

Cited by 7 publications

(1 citation statement)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This suggests that the adverse effects of both phenobarbitone and vitamin B6 upon L-dopa therapy may be mediated through an increase in dopa decarboxylase function due to enzyme indu,ction. In a case of infantile subacute necrotizing encephalopathy, Ebadi, Bostad, and Pellegrino (1969) found that in spite of an increase in the 24 hour urinary excretion of dopamine, the dopamine concentration of the striatum was markedly decreased. This was explained by a selective inhibition of dopa decarboxylase in the brain.…”

Section: Methods and Resultsmentioning

confidence: 96%

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

Klawans

Ringel

Shenker

1971

Journal of Neurology, Neurosurgery & Psychiatry

View full text Add to dashboard Cite

SUMMARY 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.In patients with Parkinsonism receiving L-dopa (L-3, 4-dihydroxyphenylalanine), vitamin B6 has recently been shown to cause a loss or reversal of the L-dopa effect (Duvoisin, Yahr, and Cote, 1969; Yahr, Duvoisin, Schear, Barrett, and Hoehn, 1970 Sourkes, 1966). There is at the present time no explanation as to why a cofactor (B6), which is necessary for conversion of dopa to dopamine, when given in excessive amounts actually inhibits the clinical effects of L-dopa. At least two different possible mechanisms could explain this. Pyridoxine in excessive amounts could increase the activity of dopa decarboxylase in the periphery. This would increase the metabolism of L-dopa, lower L-dopa blood levels, and decrease the penetration and metabolism of L-dopa within the central nervous system. It is also possible that pyridoxine could act through a mechanism not involving dopa decarboxylase.We have evaluated the effects of pyridoxine on patients receiving both L-dopa and a dopa decarboxylase inhibitor, (alpha methyl dopa hydrazine). These observations help to explain the paradoxical effects of large amounts of pyridoxine in patients receiving L-dopa. METHODS AND RESULTSSeven patients with Parkinsonism who had been on L-dopa for at least one year were included in this study. These patients ranged in age from 43 to 67 with an average age of 57 years. The patients had had Parkinsonism for an average of seven years with a range of from four to 11 years. The patients had been evaluated according to the criteria of Hoehn

show abstract

Section: Methods and Resultsmentioning

confidence: 96%