Clozapine affects the pharmacokinetics of risperidone and inhibits its metabolism and P-glycoprotein-mediated transport in vivo and in vitro: A safety attention to antipsychotic polypharmacy with clozapine and risperidone

Inflammation affects the pharmacokinetics of risperidone: Does the dose need to be adjusted during the acute-phase reaction?

BACKGROUND

Several studies have indicated that the plasma concentration of risperidone increases 3-5-fold during the acute-phase reaction (APR) of inflammation or infection. Psychiatric symptoms are present or deteriorate when the dose is lowered; thus, the complex effects of inflammation on the pharmacokinetics of risperidone need to be examined.

METHODS

We established a APR model in rabbits induced by lipopolysaccharide (LPS) and studied the effect of APR on pharmacokinetics, distribution and disposition of risperidone in vivo and in vitro.

RESULTS

Following intramuscular administration, the plasma exposures for risperidone and its active metabolite (9-hydroxyrisperidone) were increased approximately 6-fold on day 2 of inflammation. The exposure values did not change between day 2 and 5 of inflammation, nor did the metabolite-to-parent ratio before and during inflammation. Following oral administration, the increase of risperidone exposure was twice as high as that following intramuscular administration during APR. However, the concentration of risperidone and 9-hydroxyrisperidone in brain tissue was similar between the inflammatory and control groups. Moreover, the plasma protein binding (PPB) of risperidone and 9-hydroxyrisperidone associated with inflammation were all increased to >99 %. In addition, risperidone and 9-hydroxyrisperidone were not substrates of the key transporters, OATP1B3, OCT2, OAT3, MATE-1, or MATE-2 K. The expression of progesterone X receptor and P-glycoprotein was inhibited by LPS.

CONCLUSION

During APR, reduced expression of P-glycoprotein and increased PPB were responsible for increased exposure in plasma, while maintaining stable concentrations in the brain, and risperidone does not need to be dose-adjusted so as to achieve psychopharmacological outcomes.

Roles of selected non-P450 human oxidoreductase enzymes in protective and toxic effects of chemicals: review and compilation of reactions

This is an overview of the metabolic reactions of drugs, natural products, physiological compounds, and other (general) chemicals catalyzed by flavin monooxygenase (FMO), monoamine oxidase (MAO), NAD(P)H quinone oxidoreductase (NQO), and molybdenum hydroxylase enzymes (aldehyde oxidase (AOX) and xanthine oxidoreductase (XOR)), including roles as substrates, inducers, and inhibitors of the enzymes. The metabolism and bioactivation of selected examples of each group (i.e., drugs, “general chemicals,” natural products, and physiological compounds) are discussed. We identified a higher fraction of bioactivation reactions for FMO enzymes compared to other enzymes, predominately involving drugs and general chemicals. With MAO enzymes, physiological compounds predominate as substrates, and some products lead to unwanted side effects or illness. AOX and XOR enzymes are molybdenum hydroxylases that catalyze the oxidation of various heteroaromatic rings and aldehydes and the reduction of a number of different functional groups. While neither of these two enzymes contributes substantially to the metabolism of currently marketed drugs, AOX has become a frequently encountered route of metabolism among drug discovery programs in the past 10–15 years. XOR has even less of a role in the metabolism of clinical drugs and preclinical drug candidates than AOX, likely due to narrower substrate specificity.

Blood-brain barrier dysfunction in bipolar disorder: Molecular mechanisms and clinical implications

Bipolar disorder (BD) is a severe psychiatric disorder affecting approximately 1-3% of the population and characterized by a chronic and recurrent course of debilitating symptoms. An increasing focus has been directed to discover and explain the function of Blood-Brain Barrier (BBB) integrity and its association with a number of psychiatric disorders; however, there has been limited research in the role of BBB integrity in BD. Multiple pathways may play crucial roles in modulating BBB integrity in BD, such as inflammation, insulin resistance, and alterations of neuronal plasticity. In turn, BBB impairment is hypothesized to have a significant clinical impact in BD patients. Based on the high prevalence of medical and psychiatric comorbidities in BD and a growing body of evidence linking inflammatory and neuroinflammatory mechanisms to the disorder, recent studies have suggested that BBB dysfunction may play a key role in BD's pathophysiology. In this comprehensive narrative review, we aim to discuss studies investigating biological markers of BBB in patients with BD, mechanisms that modulate BBB integrity, their clinical implications on patients, and key targets for future development of novel therapies.