Hyperprolactinaemia is a significant adverse effect of antipsychotic treatment and is particularly associated with dopamine-blocking agents like risperidone. Hyperprolactinaemia may cause menstrual disturbance, galactorrhoea, impotence and reduced libido. These problems impair the quality of life and contribute to non-adherence to medication (Reference MaguireMaguire, 2002). Chronic hyperprolactinaemia has been associated with osteoporosis (Reference Naidoo, Goff and KlibanskiNaidoo et al, 2003).
Depot risperidone is an injectable, slow-release formulation whose prolactin-inducing properties may differ from oral risperidone. Only one previous trial assessed hyperprolactinaemia associated with the use of depot risperidone in routine clinical care (Reference Bushe and ShawBushe & Shaw, 2007).
In a pilot study in Renfrewshire, Scotland, we identified 37 individuals who were taking depot risperidone. Twelve individuals had medical conditions or took other drugs that may have influenced the level of prolactin and thus were excluded from our study. The remaining 25 individuals had the level of prolactin measured and they completed a questionnaire about prolactin-related side-effects. Ten individuals refused to take part in the study and it was completed by 15 participants (9 men and 6 women, mean age 48 years, mean duration of treatment with depot risperidone 15.4 months).
In 12 participants the level of prolactin has risen, with 3 individuals having levels more than four times the upper limit of normal. Only 4 participants with hyperprolactinaemia complained of any prolactin-related symptoms. One person complained of prolactin-related symptoms despite having a normal prolactin level.
The prevalence of hyperprolactinaemia in this study was 80% compared with 53% reported by Bushe & Shaw (Reference Bushe and Shaw2007).
Most individuals taking depot risperidone will have hyperprolactinaemia and reported symptoms are an unreliable guide to prolactin levels. Further study is required to inform decisions about the clinical management of this patient group.
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