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.
Keywords: adjunctive treatment; hyperprolactinemia; schizophrenia; terguride.