Antipsychotic treatment with alpha-methyltyrosine in combination with thioridazine: prolactin response and interaction with dopaminergic precursor pools.

The antipsychotic effect of alpha-methyltyrosine (alpha-MT) in combination with thioridazine was investigated by means of rating scales for "social behaviour" and "mental symptoms". The clinical effect was also evaluated in relation to the serum concentrations of alpha-MT and thioridazine and to the increase in prolactin secretion in response to the interaction with hypothalamic dopaminergic mechanisms. The interactions between the serum levels of alpha-MT and those of the transmitter precursors phenylalanine and tyrosine were analysed. The results confirmed the ability of alpha-MT (2 g/day) to potentiate the antipsychotic effect of thioridazine, whereby the dose of neuroleptic drug required to control psychotic symptoms may be markedly reduced. None of the four patients who completed the trial showed side effects that could be ascribed to alpha-MT. The antipsychotic effect of thioridazine, alone or in combination with alpha-MT, correlated well with the prolactin response in the individual patient. No important interference with serum phenylalanine or tyrosine levels was noted during treatment with alpha-MT.