Neuroleptic drug effect on plasma dopamine-beta-hydroxylase in schizophrenia.

Plasma dopamine-beta-hydroxylase (DBH) activity was determined in 8 chronic schizophrenic patients following neuroleptic treatment for 2 months. Enzyme activity was decreased by 13.7 +/- 3.4% (mean +/- SD). The difference from pre-drug levels was not statistically significant. The reduction in DBH activity stabilized after the 1st month of treatment and was unrelated to neuroleptic drug load.