Subjects
The study was based on routine TDM data collected at the Center for Psychopharmacology, Diakonhjemmet Hospital (Oslo, Norway) over the period April 2005 - August 2021. Sample information was extracted from the standard TDM requisition forms, including concomitant medication, time interval between last dose and sampling, and daily dosage. The recommended sampling time interval for atomoxetine is 4-8 hours, in concordance with the Norwegian harmonization project for ADHD-drug laboratory analysis14 and selected to coincide with primary therapeutic effect. The study criteria were serum samples of atomoxetine without (i ) use of enzyme inducers (carbamazepine, phenytoin and phenobarbital) and/or (ii ) use of CYP2D6 inhibitors (paroxetine, fluoxetine and bupropion) and (iii) availableCYP2D6 and CYP2C19 genotype records. The outcome measures of interests were (i ) dose-adjusted serum concentration (C D-1 ratio), (ii ) unadjusted serum concentrations, (iii ) daily dose, and (iv ) risk of having undetectable serum concentration of atomoxetine.
The study was approved by the Regional Committee for Medical and Health Research Ethics (REK-235205), and did not require informed patient consent, as only historical, anonymized data were included without the potential to cause any harm.