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.