Hyperprolactinemia is a frequent consequence of treatment with
antipsychotics. Earlier studies have indicated that
terguride, which is a partial
dopamine agonist, reduces the
prolactin levels that are induced by prolactinemia. Thus, we examined the dose effects of adjunctive treatment with
terguride on the plasma concentrations of
prolactin in patients with elevated
prolactin levels resulting from
antipsychotic treatment.
Terguride was concomitantly administered to 20 schizophrenic patients (10 males and 10 females) receiving
paliperidone and
risperidone. The dose of
terguride was 1.0 mg/day. Sample collections for
prolactin were conducted before
terguride (baseline) and 2-4 weeks after administration. The samples were obtained after the morning dose of
terguride. The average (± standard deviation) plasma
prolactin concentration during
terguride coadministration was significantly lower than the baseline concentration in females (82.3±37.1 ng/mL versus 56.5±28.5 ng/mL, P<0.01) but not in males (28.8±18.0 ng/mL versus 26.2±13.1 ng/mL, not significant). Additionally, a significant correlation between the ratio of
prolactin reduction and the baseline
prolactin concentration was identified in males (r s=-0.638, P<0.05) but not in females (r s=-0.152, not significant). Many patients complained of various adverse events following
terguride administration, such as
insomnia, agitation, and/or the aggravation of
hallucinations. This study suggests that additional treatment with
terguride decreases the
prolactin concentrations in females experiencing high
prolactin levels as a result of
antipsychotic treatment. However, its utility for
schizophrenia may be diminished because of its low tolerability.