Modeling of prolactin response following dopamine D2 receptor antagonists in rats: can it be translated to clinical dosing?

Prolactin, flupenthixol decanoate and first episode schizophrenia - clinical and laboratory correlates

First-episode psychosis (FEP) patients are more sensitive to neuroleptic side-effects such as hyperprolactinemia. We examined the prolactin levels of previously minimally treated patients with first episode schizophrenia over their first year of treatment with flupenthixol decanoate and the relationship between prolactin levels, gender and clinical features of schizophrenia. Prolactin levels were assessed at three monthly intervals in 126 patients with first-episode schizophrenia in a single-site study conducted over 12 months during treatment with flupenthixol decanoate according to a fixed protocol. The mean prolactin level for the total sample was 11.91 ng/ml (standard deviation [SD]15.52) at baseline. Women had higher levels of prolactin than men at month 3, 6 and 12, reaching statistical significance at month 12 (p = 0.02). At 12 months more women than men had hyperprolactinemia (defined as more than 20 ng/ml for males, and as more than 25 ng/ml for females (p = 0.007). Using a mixed effect model, there was a significant association between prolactin change scores over 12 months and gender (p = 0.025) as well as Positive and Negative Syndrome Scale (PANSS) total scores (p = 0.001). In addition female gender (p = 0.04) and age (p = 0.02) correlated with the risk of hyperprolactinemia as categorical variable. In this study treatment with flupenthixol decanoate was associated with relatively low levels of hyperprolactinemia, likely owing to flupenthixol's relatively atypical mode of action, as well as to the low doses used in our study. We found an inverse correlation between total PANSS scores and prolactin levels, which could support the suggested theory of prolactin having antipsychotic properties. Our study confirms the importance of gender on the prolactin raising effects of antipsychotic treatment.

Modeling of prolactin response following dopamine D2 receptor antagonists in rats: can it be translated to clinical dosing?

Prolactin release is a side effect of antipsychotic therapy with dopamine antagonists, observed in rats as well as humans. We examined whether two semimechanistic models could describe prolactin response in rats and subsequently be translated to predict pituitary dopamine D₂ receptor occupancy and plasma prolactin concentrations in humans following administration of paliperidone or remoxipride. Data on male Wistar rats receiving single or multiple doses of risperidone, paliperidone, or remoxipride was described by two semimechanistic models, the precursor pool model and the agonist–antagonist interaction model. Using interspecies scaling approaches, human D₂ receptor occupancy and plasma prolactin concentrations were predicted for a range of clinical paliperidone and remoxipride doses. The predictions were compared with corresponding observations described in literature as well as with predictions from published models developed on human data. The pool model could predict D₂ receptor occupancy and prolactin response in humans following single doses of paliperidone and remoxipride. Tolerance of prolactin release was predicted following multiple doses. The interaction model underpredicted both D₂ receptor occupancy and prolactin response. Prolactin elevation may be deployed as a suitable biomarker for interspecies translation and can inform the clinical safe and effective dose range of antipsychotic drugs. While the pool model was more predictive than the interaction model, it overpredicted tolerance on multiple dosing. Shortcomings of the translations reflect the need for better mechanistic models.