Possible Interaction: Dihydroxyphenylalanine and Vitamin B 6

“ Pyridoxine , a co-factor in the decarboxylation of dopa , reverses the movement disorder of l-dopa intoxication.”

“Addition of pyridoxal phosphate to the incubation mixture greatly enhanced the activity for both l‐DOPA and l‐5‐HTP.”

“ Dihydroxyphenylalanine decarboxylase and 5-hydroxytryptophan decarboxylase respectively have high and low affinities for pyridoxal phosphate.”

“A tetrahydroisoquinoline derivative did not appear to be formed when l‐DOPA and pyridoxine were administrated together suggesting that pyridoxine protected the enzyme and favored a more rapid degradation of l‐DOPA peripherally with less l‐DOPA available for the CNS.”

“The administration of l‐DOPA and pyridoxine (100 and 50mg/kg, per os, respectively) together for 7 days increased DOPA/5HTP decarboxylase activity in the brain to the same extent as did l‐DOPA and pyridoxine given individually.”

“However, nonenzymatio studies under conditions similar to those of … studies reveal that most of the inhibition by dopa , dopamine and norepinephrine is due … reaction of these compounds with pyridoxal phosphate while reaction between pyridoxal phosphate and the tryptophan derivatives, 5-… and serotonin, does not occur under the conditions employed.”