Therapeutic drug monitoring in children and adolescents using quetiapine for the treatment of schizophrenia and other psychotic disorders – results of a pharmacovigilance study

Despite quetiapine is increasingly used ‘off-label’ in children and adolescents, knowledge on its efficacy and safety is rare and no age-specific therapeutic reference ranges (TRR) have yet been established. The aim of this study was to elucidate whether the TRR described for adults is applicable in minors. Furthermore, the relationship between daily dose, serum concentration and clinical outcome of quetiapine in children and adolescents were investigated.

Data from 77 patients, recruited within the multicentre TDM-VIGIL study*, aged between 12 and 17 years were evaluated. Patient characteristics, medication data, doses, serum concentrations and therapeutic outcomes were assessed using standardised measures.

A positive correlation was observed between weight-adjusted daily dose and serum concentration (r _s = 0.580, p < 0.001), with dose variation explaining 34% (r _s ²= 0.34) of the variability in quetiapine concentrations. Generally, good clinical effectiveness, comparable to results described in adults, was observed and most patients (88.9%) experienced no or mild adverse drug reactions. A positive relationship between serum concentration and therapeutic effect was found (r _s = 0.238, p = 0.006). 38.5 % of all serum concentrations were within the recommended TRR described for adults (100-500 ng/ml). A rough calculation method hinted on a considerably lower TRR for minors (14– 290 ng/ml) compared to adults.

This study may contribute to the definition of a TRR for quetiapine in minors, yet further controlled studies with larger sample sizes are needed to verify and strengthen preliminary results.

Publication History

Article published online:
12 March 2024