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Twenty-one serum samples from 11 schizophrenic patients receiving long-term haloperidol therapy were analyzed for haloperidol concentrations by two different radioimmunoassays (RIAs) and gas chromatography (GC). There was a good correspondence between the RIA and GC values over a wide range of drug concentrations. However, compared with the specific GC technique, both RIA methods overestimated haloperidol concentrations, reflecting differences in the specificities of the two RIA antibodies. One of the RIA methods had the requisite specificity for application to patients treated with long-term haloperidol therapy, although further methodological refinement will be required for its general clinical application. Haloperidol values determined by GC and RIA analyses correlated highly with prolactin concentrations in the same samples, suggesting that the usefulness of prolactin measurement as an "in vivo bioassay" for circulating levels of haloperidol should be further explored.

Prolactin response to electroconvulsive therapy (E.C.T.)was investigated in nine patients with endogenous depression. Four patients undergoing minor gynaecological surgery who had had the same type of intravenous anaesthesia as the E.C.T. group were studied as controls. 15 minutes after E.C.T. there was a 10 to 50 fold increase in serum-prolactin in eight of the patients. The effects of anaesthesia and surgery on serum-prolactin in the controls were negligible.

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.

Plasma levels of prolactin, FSH, LH, progesterone and 17-beta-oestradiol in twenty women with premenstrual tension were compared with those in twenty controls. The former group was studied also during treatment with bromocriptine. The mean prolactin level in the PMT group was lower in the follicular phase than in the luteal phase (P less than 0.01), but there was no difference between the PMT and control group in the luteal phase. No differences were found between the controls and the PMT group in FSH,LH, 17-beta-oestradiol and progesterone levels in the luteal phase. Bromocriptine suppressed prolactin concentrations (P less than 0.01), but had no effect on the FSH, LH, 17-B-oestradiol or progesterone levels.