Relationship between plasma risperidone concentrations and clinical features in chronic schizophrenic patients in China

BACKGROUND

Prior studies have noted great variability in the plasma levels of risperidone (RIS). Plasma concentrations of RIS and its active moiety are highly variable and depend on absorption, metabolism, and other predictors of metabolic dysregulation; however, these factors are poorly understood and the association between metabolic change and change in psychopathology is uncertain.

AIM

To ascertain the characteristics of chronic schizophrenic patients treated with RIS, and to assess their relationship with plasma RIS levels.

METHODS

This was a descriptive cross-sectional study of 50 patients with a diagnosis of schizophrenic psychosis treated with RIS in a psychiatric service. The plasma concentrations of RIS and its metabolite 9-hydroxyrisperidone were determined by high performance liquid chromatography. The patients' demographic and clinical characteristics, and psychopathologies were assessed, and the associations between clinical variables and plasma levels of RIS were explored.

RESULTS

Male patients received higher doses of RIS than female ones, but plasma concentrations of RIS and risperidone + 9-hydroxyrisperidone (active moiety) were higher in female patients. Age and the mean scores of the general psychopathology subscale of the Positive and Negative Syndrome Scale (PANSS) were significantly positively correlated with plasma concentrations of risperidone + 9-hydroxyrisperidone adjusted for weight and dose in all 50 subjects. In male subjects, we found a statistically significant positive correlation between the concentrations of risperidone + 9-hydroxyrisperidone in plasma/(dose × kg) and age, mean PANSS negative subscale scores, mean PANSS general psychopathology subscale scores, and mean PANSS total scores.

CONCLUSION

Long-term use of RIS should be closely monitored in older patients and females to minimize the risk of high concentrations which could induce side effects.

Castration reduces potassium-stimulated norepinephrine release from superfused olfactory bulbs of male rats

In order to investigate the possible relationship among the olfactory bulb (OB), norepinephrine (NE) and gonadal steroids, we measured NE release from superfused anterior and posterior OB in intact and castrated male rats (Expt. I) as well as in castrated male rats implanted with either empty or testosterone filled silastic capsules (Expt. II). Both basal and potassium (K+ 30 mM)-stimulated release of NE was greater in posterior compared to anterior OB. All groups were responsive to the K+ stimuli showing increases in NE release. The degree of K(+)-stimulated release was significantly greater in intact compared to that of castrated rats. No differences in K(+)-stimulated release were observed between castrated and castrated plus testosterone-treated groups. These results demonstrate that castration of male rats significantly reduces OB noradrenergic responsiveness to K+ stimulation, an effect which was not restored following administration of silastic capsules containing testosterone.

Preferential increase in pituitary prolactin versus vasoactive intestinal peptide as a function of estradiol benzoate dose in the ovariectomized rat

Vasoactive intestinal peptide (VIP) is synthesized in various tissues, including the anterior pituitary gland, where it may stimulate the release of PRL. Because estrogen plays a central role in the regulation of PRL, it becomes important to determine the effects of this steroid on both pituitary VIP and PRL. To study this, pituitary VIP and PRL and plasma PRL were assayed in ovariectomized rats after treatment with estradiol benzoate (EB; 0.007, 0.07, 0.7, 7 or 70 microgram/rat). Pituitary and plasma TSH were also determined as well as VIP content in the medial basal hypothalamus, suprachiasmatic region, cerebral cortex, and jejunum. Oil-treated rats served as controls. Injection of 0.7 or 7 microgram EB resulted in a significant increase in pituitary PRL without changing plasma PRL levels or pituitary VIP content compared to values in the control group. Only treatment with 70 microgram EB produced a significant increase in both pituitary VIP and PRL as well as in plasma PRL compared to control values. EB treatment at any of the doses used had no significant effect on pituitary and plasma TSH or VIP content in any of the other tissues examined. These data show that pituitary PRL and VIP are differentially regulated in response to estrogen. The increases in pituitary VIP and basal plasma PRL after treatment with the highest dose of EB suggest that pituitary VIP may be involved in the development of estrogen-induced hyperprolactinemia. These data also show that the regulations of pituitary VIP and TSH are independent of each other in the estrogen-treated rat.