Pharmacokinetic Drug-Drug Interactions of Mood Stabilizers and Risperidone in Patients Under Combined Treatment

Georgios Schoretsanitis, Ekkehard Haen, Gerhard Gruender, Benedikt Stegmann, Koen R. J. Schruers, Christoph Hiemke, Sarah E. Lammertz, Michael Paulzen*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Background: The combination of anticonvulsant mood stabilizers with antipsychotic drugs may lead to clinically relevant drug-drug interactions. The objective of the study was to identify pharmacokinetic interactions of different mood stabilizers on the metabolism of risperidone (RIS) under natural conditions. Methods: A large therapeutic drug monitoring database containing plasma concentrations of RIS and its metabolite 9-hydroxy-RIS (9-OH-RIS) of 1,584 adult patients was analyzed. Four groups (n = 1,072) were compared: a control group without a potentially cytochrome interacting comedication (R-0, n = 852), a group comedicated with valproate (VPA) (RVPA, n = 153), a group comedicated with lamotrigine (LMT) (R-LMT, n = 46), and a group under concomitant medication with carbamazepine (CBZ) (R-CBZ, n = 21). Dose-adjusted plasma concentrations (C/D ratio) for RIS, 9-OH-RIS and active moiety (AM) (RIS + 9-OH-RIS), as well as metabolic ratios (RIS/9-OH-RIS) were computed. Results: Groups did not differ with regard to the daily dosage (P = 0.46). Differences were detected for the distributions of the C/D ratios for RIS, 9-OH-RIS and AM(P = 0.003, P <0.001 and P <0.001, respectively). Differences remained significant after conducting a Bonferroni correction (P = 0.0125). Pairwise comparisons of the concomitant medication groups with the control group revealed significant differences; RIS C/D ratios were significantly higher in the VPA and the LMT group than in the control group (P = 0.013; P = 0.021). However, these differences did not remain significant after Bonferroni correction. In contrast, CBZ-treated patients showed lower dose-adjusted plasma concentrations of 9-OH-RIS (P <0.001) as well as the AM (P <0.001) than the control group; this difference survived the Bonferroni correction. Conclusions: The data give evidence for pharmacokinetic interactions between RIS and different anticonvulsant mood stabilizers. Carbamazepine decreased serum concentrations of 9-OH-RIS and the AM when compared with the control group. In case of VPA and LMT, findings were less significant; hints for a weak RIS metabolism inhibition by LMT of unclear clinical significance were found.
Original languageEnglish
Pages (from-to)554-561
JournalJournal of Clinical Psychopharmacology
Issue number6
Publication statusPublished - Dec 2016


  • therapeutic drug monitoring
  • risperidone
  • carbamazepine
  • valproic acid
  • lamotrigine cytochrome P450
  • interaction
  • pharmacokinetics

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