Comparison of prolactin concentrations between haloperidol and bromperidol treatments in schizophrenic patients

The antipsychotic drug, bromperidol, is a close structural analogue of haloperidol. These two drugs also have similarities in metabolic pathways and pharmacological properties. In the present study, the prolactin concentrations in plasma during bromperidol versus haloperidol treatments were compared in the same individuals. The subjects were 22 schizophrenic inpatients, who first received bromperidol 12 mg/day for at least 2 weeks followed by haloperidol 12 mg/day. The prolactin concentration in plasma during bromperidol treatment (median and range; 24 and 7-93 ng/ml, respectively) was significantly (P< .01) lower than during haloperidol treatment (32 and 8-102 ng/ml), although the difference was small. The mean (+/- S.D.) plasma concentration of bromperidol was significantly lower than that of haloperidol (20.8+/-8.0 vs. 28.0+/-13.1 nmol/l, P<.05). Prolactin concentrations during both treatment phases correlated well in individuals (r's=.813, P<.001), while no correlation was observed between plasma concentrations of haloperidol and bromperidol (r=.053, ns). These findings suggest that slightly higher prolactin concentration does not necessarily lead to increased risk of hyperprolactinemia during bromperidol treatment compared with haloperidol treatment. In addition, it is suggested that both drugs show similar pharmacodynamic response despite the difference in pharmacokinetics in the same individuals.