Prolactin response to withdrawal of thioridazine in dementia

Abstract

Thirty-six female inpatients with a clinical diagnosis of senile dementia of the Alzheimer type were entered into a double-blind withdrawal of their established thioridazine therapy over a four-week period. Prolactin (PRL) levels were assayed at weeks 0, 2 and 4 in both groups. A significant reduction in PRL level over this period was seen in the placebo-substituted group as compared with the active-continued group. Over the same interval there was no significant change or difference between the two groups in terms of cognitive function, behaviour or physical condition. There was no correlation between PRL levels and degree of dementia or dose of thioridazine at the start of the study. This study suggests that the response to thioridazine withdrawal in senile dementia of the Alzheimer type is a reversal of pharmacological hyperprolactinaemia. The timescale and extent of this can be likened to that seen in schizophrenics and in normal volunteers. No definite evidence emerged that PRL levels might be useful as markers of disease severity or response to neuroleptic therapy.