To the Editor.—
There is a current surge of interest in studying homovanillic acid (HVA) levels as a putative index of brain dopaminergic activity in psychosis and as a gauge of the dopaminergic blocking effects of neuroleptics in the central nervous system (CNS).1,2 Davidson et al3 found robust increases in the plasma HVA level 24 hours after administration of a loading dose of haloperidol. Pickar et al1,4 have consistently found significant decreases in the plasma HVA level with more prolonged administration (three to five weeks). Previously, Harris et al5 observed increased levels of plasma HVA during two weeks of neuroleptic treatment. Although inconclusive, in the aggregate these findings suggest an initial rise in circulating levels of HVA, followed by a subsequent decrease with prolonged administration of neuroleptics.We now report that the urinary HVA level increases in schizophrenic patients after three weeks of treatment with haloperidol.