The diagnosis of hyperprolactinaemia is made when raised serum prolactin levels are found on two separate occasions. Antipsychotics affect the hypothalamic dopamine system or pituitary dopamine receptors and can result in an elevated prolactin level. The aim of the study was to evaluate the prevalence of hyperprolactinaemia in patients with schizophrenia treated with either risperidone or olanzapine.

Sixty patients with schizophrenia (DSM IV criteria) participated in this study. Their mean age was 31.1 ± 8.6 years. They remained on regimens of risperidone (n=26) or olanzapine (n=34) monotherapy. Mean duration of treatment in risperidone group (RIS) was 24.7 ± 19.2 months, in the olanzapine group (OLA) was 17.0 ± 11.3 months.

Blood samples for analysis were fasting morning samples to evaluate prolactin (two measurements).

In 92.3% treated with risperidone hyperprolactinaemia was detected and in 76.5% patients treated with olanzapine.

There was no positive correlation beetween a presence of hyperprolactinemia and age of patients treated with risperidone. Strong negative correlation was detected beetween hyperprolactinemia and age of patients treated with olanzapine. (r=-0.47) (p<0.01) hyperprolactinemia was more prevalent in younger patients.

There was strong negative correlation beetween prolactin levels and lengh of treatment in a group of patients treated with risperidone (r=-0.42) (p<0.05). Prolactin level was decreasing with longer treatment.

1. 1. Hyperprolactinaemia occurs with nearly same prevalence in patients treated with risperidone and olanzapine.

2. 2. Hyperprolactinemia affects more younger people trated with olanzapine.

3. 3. Level of prolactin decreases with longer treatment with risperidone, but not with olanzapine.