Georgios Schoretsanitis

Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology: Update 2017

Authors C. Hiemke1, 2, N. Bergemann3, H. W. Clement4, A. Conca5, J. Deckert6, K. Domschke7, G. Eckermann8, K. Egberts9, M. Gerlach9, C. Greiner10, G. Gründer11, E. Haen12, U. Havemann-Reinecke13, G. Hefner14, R. Helmer15, G. Janssen16, E. Jaquenoud17, G. Laux18, T. Messer19, R. Mössner20, M. J. Müller21, M. Paulzen11, B. Pfuhlmann22, P. Riederer6, A. Saria23, B. Schoppek24, G. Schoretsanitis25, M. Schwarz26, M. Silva Gracia12, B. Stegmann12, W. Steimer27, J. C. Stingl10, M. Uhr28, S. Ulrich29, S. Unterecker6, R. Waschgler30, G. Zernig23, 31, G. Zurek32, P. Baumann33

Risperidone-induced extrapyramidal side effects: is the need for anticholinergics the consequence of high plasma concentrations?

Antipsychotic drugs can induce various undesirable adverse motor reactions, such as extrapyramidal side effects (EPS). A widely accepted pharmacodynamic mechanism underlying EPS includes an increase in striatal D2-receptor occupancy. However, less is known about the pharmacokinetic background of EPS. The aim of this study was to analyze in-vivo possible pharmacokinetic patterns underlying biperiden-treated EPS in risperidone (RIS)-medicated patients. A large therapeutic drug monitoring database containing plasma concentrations of RIS and its metabolite 9-hydroxyrisperidone (9-OH-RIS) of 2293 adult inpatients and outpatients was analyzed. Two groups were compared: a group receiving RIS (n=772) and a group comedicated with biperiden (n=68). Plasma concentrations, dose-adjusted plasma concentrations (C/D) of RIS, 9-OH-RIS, and active moiety (AM) (RIS+9-OH-RIS) as well as ratios of concentrations for metabolite to parent drug (9-OH-RIS/RIS) were computed. We compared the plasma concentrations of the different compounds between the two groups considering the prescription of biperiden as an indirect report of EPS. The daily dosage of RIS did not differ between groups. No differences were detected in case of plasma concentrations and C/D of RIS and active metabolite between the groups. However, plasma concentrations of the AM were significantly higher in the comedicated group (P=0.032) and showed a trend in terms of the active metabolite 9-OH-RIS (P=0.053). Data indicate enhanced AM plasma concentrations of RIS in patients comedicated with biperiden as an EPS treatment. This might underscore an association between higher plasma concentrations of the AM and treatment-requiring EPS.

A systematic review and combined analysis of therapeutic drug monitoring studies for long-acting risperidone

ABSTRACT Introduction: This systematic review of therapeutic drug monitoring (TDM) identifies three long-acting injectable (LAI) risperidone formulations. Areas covered: Limited data is available on two formulations (RBP-7000 and in Situ Microparticle), but 20 TDM articles on the microsphere formulation were found. Risperidone TDM includes the serum concentrations of risperidone and its active metabolite, 9-hydroxyrisperidone, used for calculating: 1) the risperidone/9-hydroxyrisperidone (R/9-OH-R) ratio (a measure of CYP2D6; values >1 are indicative of a CYP2D6 poor metabolizer) and 2) the total risperidone concentration-to-dose (C/D) ratio (a measure of risperidone clearance with a normal value around 7 in oral risperidone). The weighted mean R/9-OH-R ratio was 0.48 (approximately twice that of oral risperidone TDM) in a combined analysis from 329 patients in 6 risperidone LAI studies without major confounders. The total C/D ratios from 297 patients in 6 risperidone LAI studies ranged from 7.4 to 9.7 ng/ml/mg/day with a weighted mean of 8.8 ng/ml/mg/day. Expert commentary: Clinicians using TDM for risperidone LAI microsphere formulation need to: 1) consider steady state to be reached ≥ 6 weeks after the first injection, 2) pay attention to a) co-medications with inducers/inhibitors, b) severe inflammations/infections, and c) hepatic/renal impairment, and 3) use Castberg’s recommendation to calculate risperidone dosing.

Body mass index (BMI) but not body weight is associated with changes in the metabolism of risperidone; A pharmacokinetics-based hypothesis.

OBJECTIVE We sought to unravel the influence of body weight and body mass index (BMI), both consistently reported as pharmacokinetic relevant parameters, on metabolism of risperidone in a naturalistic sample. METHODS Conducting non parametrical tests we sought for correlations between plasma concentrations of RIS, 9-OH-RIS and AM and body weight and BMI in patients out of a therapeutic drug monitoring (TDM) database. Further, we stratified patients to three groups based upon BMI values and compared drug concentrations between groups. RESULTS Although body weight failed to correlate with pharmacokinetic parameters, BMI was positively correlated with plasma concentrations of the active metabolite (9-OH-RIS) (rs=0.121, p=0.002) and active moiety (sum of RIS+9-OH-RIS) (rs=0.128, p=0.001) as well as dose adjusted plasma concentrations of the active moiety (rs=0.08, p=0.04). The comparison of pharmacokinetic parameters between different BMI groups yielded lower plasma concentrations of 9-OH-RIS in patients with low BMI (<20kg/m2) and higher plasma concentrations of the active moiety in obese patients (BMI ≥30kg/m2) when compared with the control group (30>BMI≥20kg/m2). By comparing low vs. high BMI patients, the latter group showed higher 9-OH-RIS plasma concentrations. CONCLUSIONS AND LIMITATIONS Considerable alterations in metabolism of risperidone were detected when comparing obese and cachectic patients with the control group in alignment with the positive correlation between BMI values and plasma concentrations of the active metabolite and active moiety as well as dose adjusted plasma concentrations of the active moiety. We suggest changes in CYP2D6 or CYP3A4 activity or differences in P-glycoprotein function in obese patients with greater BMI as a plausible mechanism underlying these alterations.

Pharmacokinetic considerations in the treatment of hypertension in risperidone-medicated patients – thinking of clinically relevant CYP2D6 interactions

Background: Treatment of arterial hypertension in patients with severe mental illnesses often results in polypharmacy, potentially leading to drug-drug interactions. The objective of the study was to analyse the in vivo inhibitory potential of two antihypertensive drugs, amlodipine and metoprolol on CYP2D6 catalysed 9-hydroxylation of risperidone (RIS). Methods: A therapeutic drug monitoring database with plasma concentrations of RIS and 9-hydroxyrisperidone (9-OH-RIS) of 1584 patients was analysed. Three groups were considered; a group of patients receiving RIS without a potentially cytochrome influencing co-medication (control group, R0, n=852), a group co-medicated with amlodipine (RA, n=27) and a group, co-medicated with metoprolol (RM, n=41). Plasma concentrations, concentration-to-dose ratios (C/Ds) of RIS, 9-OH-RIS and the active moiety (AM), as well as the metabolic ratios were computed and compared using the Kruskal-Wallis test, the Mann-Whitney U test and the Jonckheere-Terpstra test to determine the means and different patterns of distribution of plasma concentrations as well as the concentration-to-dose ratios. Results: The median daily dosage of RIS did not differ between the groups (p=0.708). No differences were found in median plasma concentrations of RIS, 9-OH-RIS and AM. However, concentration-to-dose ratios for RIS, 9-OH-RIS and AM were significantly higher in the amlodipine group (p=0.025, p=0.048 and p=0.005). In the metoprolol group, the concentration-to-dose ratio for RIS was significantly higher than in the control group (p=0.017), while the C/D for 9-OH-RIS and AM was not. Conclusions and limitations: Our data show a potential pharmacokinetic interaction, most likely via CYP3A4 between amlodipine and RIS, reflected in significantly different C/Ds for RIS, 9-OH-RIS and AM. Although the interaction did not result in significantly higher plasma levels, changes in C/Ds and their distribution with regard to the median concentrations were observed.

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

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 (R0, n = 852), a group comedicated with valproate (VPA) (RVPA, n = 153), a group comedicated with lamotrigine (LMT) (RLMT, n = 46), and a group under concomitant medication with carbamazepine (CBZ) (RCBZ, 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.

Sertraline in pregnancy – Therapeutic drug monitoring in maternal blood, amniotic fluid and cord blood

RATIONALE This study is the first to measure and correlate sertraline concentrations in maternal blood, amniotic fluid and umbilical cord blood and account for distribution of the drug between these three compartments. METHODS Concentrations of sertraline were measured in six mother infant pairs at the time of delivery. Data are provided as median values, first and third quartiles as well as ranges. To account for the penetration ratio into amniotic fluid and cord blood, the concentration of sertraline in both environments was divided by the concentration in maternal serum. Daily doses were correlated with maternal serum- and umbilical cord blood-concentrations, and serum levels were correlated with levels in amniotic fluid. RESULTS The median daily dose of sertraline was 75mg (Q1: 43.75mg, Q3: 100mg; range 25-100mg). Amniotic fluid concentrations of sertraline strongly correlated with the daily dose (r=0.833, p=0.039) while neither maternal serum concentrations nor cord blood concentrations correlated with the daily dose (p>0.05). The median penetration ratio for sertraline into amniotic fluid was 0.57 (Q1: 0.28, Q3: 0.75; range: 0.22-0.88). The median penetration ratio into the fetal circulation, calculated on the basis of umbilical cord blood-concentrations, was found to be 0.36 (Q1: 0.28, Q3: 0.49; range: 0.17-0.65). CONCLUSIONS Sertraline concentrations in amniotic fluid gave evidence that maternally administered sertraline is constantly accessible to the fetus via amniotic fluid in a manner not previously appreciated. A relatively low penetration into fetal circulation may contribute to a sufficient safety profile of sertraline during pregnancy although in our study APGAR Scores were relatively low in three infants. Our data support the important role of therapeutic drug monitoring in maintaining the safety of pregnant women and exposed infants.

Pregnancy exposure to citalopram – Therapeutic drug monitoring in maternal blood, amniotic fluid and cord blood

RATIONALE Aim of the study was to measure and correlate citalopram concentrations in maternal blood, amniotic fluid and umbilical cord blood to account for the distribution of the drug between these three compartments. METHODS Concentrations of citalopram were measured in twelve mother infant pairs at the time of delivery. Data are provided as median values, first (Q1) and third (Q3) quartiles as well as ranges. To account for the penetration ratio into amniotic fluid and cord blood, the concentration of citalopram in was divided by the concentration in maternal serum. Correlations between daily dosage, maternal serum concentrations and umbilical cord blood concentrations were computed for twelve patients. As amniotic fluid was only available for nine mother infant pairs, appropriate calculations are provided for these mother-infant pairs. RESULTS The median daily dosage of citalopram was 20mg (Q1: 10mg, Q3: 20mg; range 10-40mg). The relation between the daily dosage of citalopram and its concentrations in maternal serum was highly significant (r=0.667, p=0.018). Maternal serum concentrations and cord blood concentrations were positively correlated (r=0.790, p=0.002) with a median penetration ratio into the fetal circulation of 0.78 (Q1: 0.52, Q3: 1.16, range 0.46-1.66). The median penetration ratio into amniotic fluid was 1.8 (Q1: 1.07, Q3: 2.64; range 0.52-6.97). CONCLUSIONS Citalopram concentrations in amniotic fluid and cord blood give evidence that maternally administered citalopram is constantly accessible to the fetus via amniotic fluid. A high correlation between maternal serum concentrations of citalopram and umbilical cord blood concentrations highlights a predictive role of quantifying drug concentrations in maternal serum for assessing drug concentrations in the fetal circulation. Findings support the important role of therapeutic drug monitoring in maintaining the safety of pregnant women and exposed infants.

TDM in psychiatry and neurology: A comprehensive summary of the consensus guidelines for therapeutic drug monitoring in neuropsychopharmacology, update 2017; a tool for clinicians*

Abstract Objectives: Therapeutic drug monitoring (TDM) combines the quantification of drug concentrations in blood, pharmacological interpretation and treatment guidance. TDM introduces a precision medicine tool in times of increasing awareness of the need for personalized treatment. In neurology and psychiatry, TDM can guide pharmacotherapy for patient subgroups such as children, adolescents, pregnant women, elderly patients, patients with intellectual disabilities, patients with substance use disorders, individuals with pharmacokinetic peculiarities and forensic patients. Clear indications for TDM include lack of clinical response in the therapeutic dose range, assessment of drug adherence, tolerability issues and drug–drug interactions. Methods: Based upon existing literature, recommended therapeutic reference ranges, laboratory alert levels, and levels of recommendation to use TDM for dosage optimization without specific indications, conversion factors, factors for calculation of dose-related drug concentrations and metabolite-to-parent ratios were calculated. Results: This summary of the updated consensus guidelines by the TDM task force of the Arbeitsgemeinschaft für Neuropsychopharmakologie und Pharmakopsychiatrie offers the practical and theoretical knowledge for the integration of TDM as part of pharmacotherapy with neuropsychiatric agents into clinical routine. Conclusions: The present guidelines for TDM application for neuropsychiatric agents aim to assist clinicians in enhancing safety and efficacy of treatment.

Effect of smoking on risperidone pharmacokinetics – A multifactorial approach to better predict the influence on drug metabolism

PURPOSE To disentangle an association between tobacco smoking, smoking habits and pharmacokinetic patterns such as plasma concentrations of risperidone (RIS), its active metabolite 9-hydroxyrisperidone (9-OH-RIS) and the active moiety, AM, (RIS+9-OH-RIS) in a naturalistic sample. METHODS Plasma concentrations, dose adjusted plasma concentrations (C/D) of RIS, 9-OH-RIS and AM in patients out of a therapeutic drug monitoring (TDM) database were compared between smokers (n=401) and non-smokers (n=292). RESULTS Daily dosage of risperidone differed significantly with smokers receiving higher doses than patients in the control group (p=0.001). No differences were detected in plasma concentrations of the active moiety, RIS and 9-OH-RIS (p=0.8 for AM, p=0.646 for RIS and p=0.538 for 9-OH-RIS). However, dose corrected concentrations (C/D) of metabolite (C/D 9-OH-RIS) and active moiety (C/D AM) differed between significantly between groups (p=0.002 and p=0.007). After stratifying smokers to a group of moderate smokers (<20cigarettes/day) (RS1, n=109) and a group of heavy smokers (≥20cigarettes/day) (RS2, n=135), the comparison between non-smokers and both groups only showed lower values of C/D for 9-OH-RIS (p=0.011) for the group of moderate smokers while other pharmacokinetic parameters did not differ. CONCLUSIONS Apart from the well-known induction of CYP1A2 activity by polycyclic aromatic hydrocarbons, smoking might exert an effect on other CYP isoenzymes as well. A possible interpretation proposes a slight inducing effect of smoking on risperidone metabolism most likely via CYP3A4.