Serum vitamin B-6 in schizophrenic and schizoaffective patients with and without tardive dyskinesia

There are several reports regarding the efficacy of vitamin B-6 in the trea tment of tardive dyskinesia (TD). Vitamin B-6 plays a key role in the synth esis of several neurotransmitters, including serotonin, dopamine, norepinep hrine, and gamma-aminobutyric acid, all of which have been proposed to be i nvolved in the development of TD. The purpose of this study was to examine whether there are special markers to distinguish long-term neuroleptic expo sure patients who have TD from these patients who do not develop this side effect. in view of the pivotal role of vitamin B-6 in the synthesis of all neurotransmitters believed to take part in the pathogenesis of TD, we decid ed to examine whether basal levels of vitamin B-6 might explain the differe nce between these two groups. Such a finding could provide a predictive mar ker for vulnerable patients. The active metabolite of vitamin B-6 is pyrido xal phosphate (PP). Pyridoxal phosphate blood levels were measured in 15 sc hizophrenic and schizoaffective patients with TD and compared with 15 patie nts without evidence of TD (matched by sex, age, smoking, and diagnosis). W e found that, although patients in the TD group were exposed to neuroleptic drugs for significantly longer periods of time, there were no differences in serum PP levels between the groups. The reports of the effectiveness of vitamin B-6 supplementation in the treatment of TD could therefore be expla ined by the assumption that central nervous system or intracellular vitamin B-6 levels, which are involved in the pathogenesis of TD, are not the same as vitamin B-6 peripheral serum levels. There is need for further studies, which will clarify the relationship between vitamin B-6 and TD.