Therapeutic Drug Monitoring (TDM) of children and adolescents with tic disorders treated with tiapride

Tiapride is used off-label as first-line treatment for children and adolescents with tic disorders in German speaking countries. Standardized TDM data were collected from 2007 to 2014 within the Competence Network Therapeutic Drug Monitoring in Child and Adolescent Psychiatry (www.tdm-kjp.com) to investigate the correlation between dosage, serum concentration, effectiveness and adverse drug reactions (ADRs) of tiapride. Additionally, information about a possible age- and diagnosis-specific therapeutic reference range should be obtained as the therapeutic reference ranges for tiapride are only available for adult patients with dyskinesia (1000 to 2000 ng/ml). In the 49 paediatric patients (mean age = 12.5 years, 84% male), a positive correlation (r = 0.76; p <.001) was found between tiapride dose (mean = 353.6 mg) and serum concentration (mean = 1324.0 ng/ml) with marked interindividual variability, but no relationship between serum concentration and effect (83.3% profit) nor ADRs. No patient suffered from severe ADRs and only a few patients had mild or moderate ADRs (n = 13). ROC analysis revealed a sensitivity of 80% from a concentration of 897 ng/ml in regard to the therapeutic response. These results suggest that the lower therapeutic reference range in adolescent patients with tic disorders could be about 900 ng/ml.