6.2. Supplementary Material

Quantification of risperidone and 9-OH-risperidone

Blood was asked to be drawn just before drug administration (trough concentration) at steady state (> 5 elimination half-lives under the same drug dose). Risperidone and 9-OH-risperidone concentrations were determined by HPLC with ultraviolet detection (HPLC/UV) [53]. The method was validated according to DIN 32645 (Deutsche Industrie Norm 32645, described in guidelines of GTFCh (Society of Toxicology and Forensic Chemistry) in consideration of ISO 5725 (International Organization for Standardization) [54], FDA (US Food and Drug Administration) guidances[55]and ICH (International Conference on Harmonization) requirements [56]. The laboratory regularly runs internal quality controls and participates in external quality assessment schemes by INSTAND (Düsseldorf, Germany, The limit of detection (LOD) defined as signal to noise ratio of 3:1, was 5 ng/ml for both risperidone as well as 9-OH-risperidone. The inter-day precision, determined as duplicates on three different days, at 5 ng/ml was 5.56 % of mean and 5.21 % of mean, respectively. Usually twice the limit of detection is accepted as limit of quantification (LOQ). However, the analytical process using HPLC with ultraviolet detection (HPLC/UV) also detects both, risperidone and 9-OH-risperidone values below the LOQ, and we decided to include these defined values into our analysis. The HPLC revealed true values above 0, i.e. the detected values were true values above zero. If we would have omitted theses values, this would have led to the fact that patients with RIS or 9-OH-RIS values below the LOQ were excluded from the analysis, what – to our understanding would have led to an incomplete analysis of the plasma concentrations.

Table 4: Median plasma and dose-adjusted(C/D) concentrations (range) and metabolic ratios of risperidone in different daily dosage groups (<6mg/day and ≥6mg/day)

Daily dosage RIS (mg/day) / <6mg/day / P values / ≥6mg/day / P values
ADR / no ADR / ADR / no ADR
number / 80 / 257 / 17 / 141
RIS (ng/mL) / 3.15 (0.4-57.0) / 3.1 (0.2-58.0) / 0.892 / 6.4 (1.0-46.0) / 7.4 (0.3-115.0) / 0.452
9-OH-RIS (ng/mL) / 16.0 (0.4-87.0) / 13.0 (0.3-73.1) / 0.065 / 26.0 (5.4-61.0) / 27.0 (1.0-142.0) / 0.499
RIS+9-OH-RIS (ng/mL) / 20.65 (1.8-91.7) / 19.0 (2.0-108.8) / 0.224 / 34.4 (16.3-96.0) / 39.8 (5.5-218.0) / 0.623
9-OH-RIS/RIS / 4.43 (0.07-32.5) / 3.6 (0.08-125.0) / 0.983 / 2.79 (0.14-26.0) / 4.33 (0.04-53.33) / 0.297
C/D RIS (ng/mL)/(mg/d) / 1.25 (0.1-28.5) / 1.07 (0.05-19.33) / 0.983 / 1.06 (0.17-7.67) / 1.0 (0.05-19.17) / 0.291
C/D 9-OH-RIS (ng/mL)/(mg/d) / 5.0 (0.2-29.0) / 4.25 (0.08-42.0) / 0.026 / 4.33 (0.9-10.17) / 4.16 (0.17-23.67) / 0.79
C/D RIS+9-OH-RIS (ng/mL)/(mg/d) / 7.1 (0.9-33.0) / 6.0 (0.5-44.67) / 0.164 / 5.73 (2.72-16.0) / 5.5 (0.92-36.33) / 0.933

RIS: plasma concentration of risperidone, 9-OH-RIS: plasma concentration of 9-OH-Risperidone, RIS+9-OH-RIS: plasma concentration of active moiety, 9-OH-RIS/RIS: metabolic ratio, C/D RIS, C/D 9-OH-RIS and C/D RIS+9-OH-RIS: dose adjusted plasma concentration of the aforementioned parameters

Figure 1: Significantly higher dose adjusted serum concentrations for the active metabolite, 9-OH-RIS, were found in the group of patients that complained ADRs.

‘Place figure 1 about here’