Increasing attention is paid to importance of hyperprolactinaemia. Sexual dysfunction and osteoporosis are reported in such patients. There is little naturalistic data showing prevalence and severity of hyperprolactinaemia in asymptomatic patients receiving antipsychotics.

All outpatients in a community mental health team in Halifax receiving antipsychotics with diagnosis of schizophrenia or bipolar disorder had prolactin measurements. Upper Limit of Normal (ULN) prolactin 500mIU/L (males) and 700mIU/L (females).

Prolactin levels were obtained in 226 patients providing 253 incident cases as antipsychotic changes were made over 36-month period.

Abnormal values were found in 49% females and 29% males - 39% of the cohort. Levels >1000 mIU/L were seen in 23% (females 36%, males 10%). From the 61/125 females with abnormal levels, 74% of these had levels >1000 mIU/L and 16/125 (13%) >2000 mIU/L. Only 13/128 males had levels >1000 mIU/L. Prevalence of hyperprolactinaemia in those on antipsychotic monotherapy: olanzapine 7%, typicals 33%, amisulpride 92%, Clozapine 4%, risperidone oral 83%, and risperidone consta 65%. In Risperidone Consta patients, 15/23 (65%) had hyperprolactinaemia including 100% of females (10/10). Most females on oral risperidone (12/13) also had hyperprolactinaemia and had values >1000 mIU/L in11/12.

Routine prolactin screening showed abnormal values in 39% and significantly abnormal levels (>1000 mIU/L) that could lead to drug/dosage alterations in 23%. Exceptionally high levels >2000 mIU/L were found in 7%. Females on oral and consta risperidone may be particularly at risk of the effects of hyperprolactinaemia.