Therapeutic drug monitoring of children and adolescents treated with aripiprazole: observational results from routine patient care.

Although aripiprazole is one of the most used antipsychotics, knowledge about serum concentrations in children and adolescents is scarce and age-specific therapeutic ranges have not been established yet. Data of a routine therapeutic drug monitoring service were analyzed in order to evaluate the relationship between dose and serum concentration of aripiprazole in children and adolescents. The study also aimed to evaluate whether the therapeutic reference range defined for adults with schizophrenia (100-350 ng/ml) is applicable for minors. Data from 130 patients (aged 7-19 years) treated with aripiprazole for different indications in doses of 2-30 mg/day were evaluated. Patient characteristics, doses, serum concentrations and therapeutic outcome were assessed by standardized measures. A positive mean correlation between body weight-corrected daily dose and aripiprazole concentration was found (rp = 0.59, p < 0.001) with variation in dose explaining 35% of the variability in serum concentrations. Girls had on average 41% higher dose-corrected concentrations than boys (244.9 versus 173.4 mg/l; p = 0.006). Aripiprazole concentrations did not vary with co-medication (p = 0.22). About 70% of all measured serum concentrations were within the recommended therapeutic range for adults. Using a calculation method in all responding patients with an ICD-10 F2 diagnosis for a rough estimation of a preliminary therapeutic window also demonstrated a similar therapeutic range of aripiprazole in minors (105.9-375.3 ng/ml) than for adults. If confirmed in larger samples and more controlled study designs, these data may contribute to the definition of a therapeutic range of aripiprazole concentrations in children and adolescents.

Therapeutic Drug Monitoring in Children and Adolescents Under Pharmacotherapy With Olanzapine in Daily Clinical Practice.

BACKGROUND: The relationship between daily dose, serum concentrations, and clinical outcomes of olanzapine as well as the influencing factors thereof in children and adolescents treated for different psychiatric disorders were investigated in daily clinical practice. In addition, it was examined whether the current recommended therapeutic range (TR) for adult patients with psychotic disorders is valid for minors. METHODS: The Competence Network for Therapeutic Drug Monitoring (www.tdm-kjp.com) routinely collects demographic and clinical outcome data as well as serum concentrations of children and adolescents treated with psychotropics. The therapeutic effect is documented using the Clinical Global Impression Scale subscale for Global Improvement. Adverse drug reactions (ADRs) are assessed using the Udvalg for Kliniske Undersogelser-Side Effect Rating Scale. RESULTS: One hundred fifteen patients (mean age = 15.9 years; range = 10.4-18.8 years; 40.9% male) were included. The majority (72.1%) was cotreated with other psychotropic drugs. A positive medium linear relationship (r = 0.619; P < 0.001) between olanzapine dose (mean = 11.64 mg/d) and serum concentration (mean = 35.65 ng/mL) was found with a marked interindividual variability of serum concentrations. Neither relationship between olanzapine serum concentration and treatment response (clinical benefit documented in 80%) nor ADRs (documented in 53.3%, in 7.5% judged as severe) was detected. Most of the patients with psychotic and eating disorders (68.8% and 71.8%, respectively) had an olanzapine serum concentration within the TR suggested for adults. CONCLUSIONS: There are several limitations of this study because of the naturalistic design, and our results should therefore be interpreted with caution. As most of the patients showed a clinical benefit under olanzapine concentrations within the TR for adults and only a minority had severe ADRs, it is reasonable to conclude a similar TR for children, adolescents, and adults.

Relationship Between Daily Dose, Serum Concentration, and Clinical Response to Quetiapine in Children and Adolescents with Psychotic and Mood Disorders.

Introduction In child and adolescent psychiatry, therapeutic drug monitoring (TDM) is strongly recommended. However, therapeutic ranges (TR) are defined only for adults. The objectives of this naturalistic study were to assess the relationships between serum quetiapine concentration, daily dose, and clinical outcomes as well as the determinants of pharmacokinetic variability. Furthermore, it was elucidated whether the recommended TR for adult patients with psychotic disorders is valid for children and adolescents. Methods TDM was performed in 180 pediatric patients treated with quetiapine. Psychopathological changes were assessed by the Clinical Global Impression - Improvement scale (CGI-I). Adverse drug reactions (ADRs) were assessed by using a short form of the Udvalg for Kliniske Undersogelser (UKU) side effect rating scale. Results A weak positive linear relationship between daily dose (mean 349.9±248.9 mg/day) and serum concentration of quetiapine (rs=0.496, p<0.001) was found (mean age 15.6±1.9 years, 45.6% male, 31.1% monotherapy), but no relationship between serum concentration and clinical outcome was found. Dose variation accounted for only 12.5% (rs2=0.125) of the variability of serum concentrations. No effects by gender, age, body weight, smoking habits, and co-medication were found. The majority of patients with psychotic (67.8%) and mood disorders (74.5%) showed a serum concentration below the suggested lower limit (100 ng/mL) of the TR for adults. Discussion There are several limitations of this study because of the naturalistic design, and our results should therefore be interpreted with caution. Notwithstanding, our data suggest that the lower limit of the TR for quetiapine is lower than the limit in adult patients.

Relationship between clozapine dose, serum concentration, and clinical outcome in children and adolescents in clinical practice.

Information on dose- and concentration-related clinical effects of clozapine treatment in children and adolescents is scarce. This study aimed to examine the relationship between dose, serum concentration, and clinical outcome as well as the influencing factors thereof in paediatric patients treated with clozapine. Data from a routine Therapeutic Drug Monitoring (TDM) service between 2004 and 2014 were studied in 68 patients, aged 11-18 years. Severity of illness, therapeutic effectiveness and adverse drug reactions (ADRs) were assessed by standardized means. A relationship between the daily dose (mean 319 mg, 4.9 mg/kg) and serum concentration (mean 387 ng/ml) of clozapine was found with the variation in dose explaining 30 % of the variability in clozapine serum concentrations. Also gender contributed to the variability, however, no influence of age or concomitant medications was detected. Furthermore, a significant association was found between clozapine serum concentration and the occurrence of ADRs. Patients without ADRs had a lower mean serum concentration than those with mild (261.4 vs 407.3 ng/ml, P = 0.018) and moderate ADRs (261.4 vs 416.3 ng/ml, P = 0.028). As clozapine was estimated to be effective in lower blood concentrations, guidance on a possibly lower therapeutic range of clozapine serum levels in paediatric patients is provided. With ADRs increasing under higher concentrations, TDM is strongly recommended in paediatric clozapine therapy for individualized dosing. Dose adjustment in females also might be reasonable according to gender-related differences in serum concentrations. However, regarding the limitations of this study results should be validated in larger studies with more standardized designs.

Interaction of valproic acid and amitriptyline: analysis of therapeutic drug monitoring data under naturalistic conditions.

Amitriptyline (AMI) and valproic acid (VPA) are common psychotropic drugs which are frequently used in psychiatry and also administered in neurology or anesthesia in the absence of a psychiatric indication. On the basis of the case of a 73-year-old man with therapy-resistant major depressive episode who experienced anticholinergic delirium after adding VPA to AMI, we retrospectively analyzed therapeutic drug monitoring data of the years 2008 to 2010. We assessed cases receiving a combination of AMI and VPA, and obtained a control sample of AMI patients without VPA which were matched for sex, age, daily dose, and comedication. Both samples were compared regarding the serum levels of AMI and nortriptyline (NOR) as well as the ratio of NOR and AMI with the Mann-Whitney U test. The combination of AMI and VPA led to a remarkable increase of AMI and NOR serum levels. When comparing 33 patients who received comedication with VPA versus 33 matched controls, the total concentration by combining mean AMI and NOR serum levels (237.1 [119.9] vs 126.4 [52.8] ng/mL) and NOR/AMI ratio (1.300 [0.905] vs 0.865 [0.455]) was significantly higher. Both AMI and VPA are widely prescribed drugs. A combination of both is common for psychiatric or neurologic patients. A cautious dosing of AMI with VPA comedication is advisable, and therapeutic drug monitoring should be performed because this combination may lead to a remarkable increase of AMI and NOR serum levels.

The relation between dosage, serum concentrations, and clinical outcome in children and adolescents treated with sertraline: a naturalistic study.

OBJECTIVE: This naturalistic therapeutic drug monitoring (TDM) study aimed to evaluate the relationship between dosage, serum concentration, and clinical outcome in children and adolescents treated with the serotonin reuptake inhibitor sertraline for different indications. METHODS: Steady-state trough serum concentrations were analyzed in 90 subjects, treated with 25-200 mg sertraline per day. Therapeutic efficacy was assessed by the Clinical Global Impression Improvement subscale and side effects by the Udvalg for Kliniske Undersogelser-Side Effect Rating Scale. RESULTS: In the study population, children were administered higher body weight normalized daily doses than adolescents. The relationships between sertraline daily dosage and serum concentrations (rs = 0.67, P < 0.0001) as well as between body weight normalized daily doses and serum concentrations (r = 0.62, P < 0.0001) were linear. In the whole patient group, no correlation between serum concentrations and either the therapeutic effect or side effects could be observed, neither significant effects of gender, age, concomitant medications, or smoking habits. When analyzing just the patients with depression, those with side effects had significantly higher sertraline serum concentrations than those without (44.8 ng/mL versus 22.3 ng/mL, P = 0.01). In general, occurrence of side effects was significantly more frequent in patients with psychiatric comedication (37.9%) than those without (11.5%, P = 0.002). DISCUSSION: As this study has the typical limitations of naturalistic studies, the results should be interpreted cautiously. From the data, it is not possible to suggest an age-specific therapeutic window for children and adolescents. However, as the intraindividual variability of sertraline serum concentrations is known to be low, TDM may certainly help to predict serum concentrations after dose adjustment, to assess pharmacokinetic drug-drug interactions influencing serum concentrations and the patient's compliance, finally allowing for personalizing dose through TDM.