Prolactin responses to domperidone in chronic schizophrenia

Review of serum prolactin levels as an antipsychotic-response biomarker

Antipsychotics acting as antagonists at dopamine D2 receptors concentrated in the striatum are the cornerstone of effective treatment of psychosis. Substantial progress in treating persons with schizophrenia could be achieved by the identification of biomarkers which reliably determine the lowest efficacious dose of antipsychotics. Prolactin levels have been considered a promising treatment-response biomarker due to dopamine’s regulation of serum prolactin levels through D2 receptors in the hypothalamic-pituitary pathway. Prolactin secretion in response antipsychotic administration is associated with the antipsychotics affinity for D2 receptors. This review assesses the available literature on the use of serum prolactin levels as an antipsychotic-response biomarker. Articles were identified through PubMed as well as the reference lists of full text articles available online. Relevant publications were summarized briefly to define the limitations and utility of serum prolactin levels as a tool for improving antipsychotic dosing. Serum prolactin levels in combination with prolactin-inducing potencies for each antipsychotic may help identify the lowest effective dose of antipsychotic medications. , In addition to the fact that prolactin secretion is dependent on serum antipsychotic levels and not brain levels, recent findings show that prolactin release is independent of the β-arrestin-2 pathway and GSK3β regulation, one branch of the pathway that has been implicated in antipsychotic efficacy. Therefore, serum prolactin is an indirect biomarker for treatment response. Further investigations are warranted to characterize prolactin-antipsychotic dose-response curves and systematically test the utility of measuring prolactin levels in patients to identify a person’s lowest efficacious dose.

Prolactin and psychopathology in schizophrenia: a literature review and reappraisal

Secretion of the anterior pituitary hormone prolactin can be significantly increased by antipsychotic drugs, leading to a range of adverse effects in patients with schizophrenia. However, there is evidence from a variety of studies that prolactin may also be related to symptom profile and treatment response in these patients, and recent work has identified variations in prolactin secretion even in drug-free patients. In this paper, a selective review of all relevant studies pertaining to prolactin and schizophrenia, including challenge and provocation studies, is presented. The implications of this work are discussed critically. A tentative model, which synthesizes these findings and argues for a significant role for prolactin in the development of schizophrenia, is outlined.

An abnormal relation between basal prolactin levels and prolactin response to 12.5 microg TRH i.v. in drug-naïve patients with first-episode schizophrenia

At doses lower than those needed to stimulate prolactin release directly, TRH almost completely antagonizes the inhibitory effect of dopamine on prolactin release. We have previously reported that prolactin response to administration of 12.5 microg TRH i.v. correlates with prolactin response to 0.5 mg i.m. haloperidol and negatively with 24-h urinary excretion of HVA in normal subjects, suggesting that the response reflects dopamine activity. An association between central dopamine hyperactivity and SANS scores relating to poverty of content of speech and inattention has been suggested by studies utilizing methylphenidate administration in patients with first-episode schizophrenia. The hypothesis that small plasma prolactin responses to administration of 12.5 microg TRH i.v. (Delta prolactin) correlate with SANS scores for these symptoms was tested in 19 drug-naïve patients with first-episode schizophrenia. Significant negative correlations were found between the response and scores relating to poverty of content of speech (r = - 0.55, p = 0.014) and inattention (r = - 0.52, p = 0.022), supporting the hypothesis of increased dopamine activity in association with disorganization symptoms. A significant positive correlation between basal prolactin levels and prolactin response to stimulation by 12.5 microg TRH was also found (r = + 0.61, p = 0.0058). Our previous study in normal subjects found a similar positive correlation between basal prolactin levels and prolactin response to stimulation by 200 microg TRH i.v., but not by 12.5 microg TRH i.v. As far as we know, this is the first study to report an abnormality in TRH-induced prolactin release in acute schizophrenia.

Determination of domperidone in human serum and human breast milk by high-performance liquid chromatography-electrospray mass spectrometry

A sensitive and selective method for the determination of domperidone in human breast milk and serum has been developed. The same method may be successfully applied to both matrices to a lower limit of quantitation of 0.5 ng/ml. Samples are processed by a liquid-liquid extraction, and analyzed by LC-ESI-MS in positive ion mode. There was no interference, on the domperidone quantitation, from over 30 drugs. Samples from patients, at various times post-dose, were analyzed and a large number showed significant levels of domperidone in the breast milk as well as in the serum.

Psychoneuroendocrinology of schizophrenia

The study of psychoneuroendocrinology of schizophrenia has yielded an extensive but inconclusive body of data. Investigations to date have been limited by several factors, including the confounding effects of neuroleptic drugs, methodological limitations, and lack of appreciation for the heterogeneity of the illness. Previously, the focus of research has been on the measurement of anterior pituitary hormones, guided by the assumptions that these hormones are regulated by the central nervous system (CNS) to a significant degree and that the unique anatomic relationship of the pituitary gland to the hypothalamus and the CNS is potentially relevant. Patients with schizophrenia do appear to have distinct endocrinologic profiles. However, although the hormonal differences between patients with schizophrenia and the general population appear to be subtle in magnitude. Nonetheless, investigation, and the exploration of the possible effect of gonadal and posterior pituitary hormones merits particular attention.