Prolactin levels in antipsychotic treatment of patients with schizophrenia carrying the DRD2*A1 allele.

Background: Hyperprolactinaemia induced by D(2) dopamine receptor antagonist antipsychotic medication can result in significant health problems.

Aims: To examine the role of DRD2 polymorphism on prolactin levels in patients treated with antipsychotic medication.

Method: Antipsychotic drugs with different degrees of D(2) receptor binding were given to 144 patients with schizophrenia. Serum prolactin levels were obtained and Taq1A DRD2 alleles were determined.

Results: Prolactin levels increased across medication groups reflecting increasingly tight D(2) receptor binding (clozapine, olanzapine, typical antipsychotics and risperidone). In the combined medication group, patients with the DRD2(*)A1allele had 40% higher prolactin levels than patients without this allele. In patients treated with clozapine (the loosest D(2) receptor binding agent), patients with the DRD2(*)A1allele had prolactin levels twice those of patients without this allele.

Conclusions: Patients with the DRD2A1 allele receiving antipsychotic medications had higher prolactin levels and were overrepresented among those with hyperprolactinaemia, suggesting greater functional D(2) receptor binding in this group.