PRL and hyperpituitarism: Chlorpromazine leads to hyperprolactinaemia in the beginning of treatment, a few hours after the first intramuscular or oral intake and persists throughout the whole therapy project [43]. Flupenthixol has been reported as a half-atypical antipsychotic and elevates serum prolactin levels 2-3 fold in the first month, but these levels normalize in a few months' period.