Onset of Atomoxetine's Therapeutic Effects

Introduction to Atomoxetine's Effects

The American Academy of Child and Adolescent Psychiatry notes that atomoxetine generally takes 6 to 12 weeks to demonstrate complete therapeutic effects, although some initial improvements can be observed as early as the first week of treatment 1, 2
The onset of action of atomoxetine differs significantly from stimulants, which have a much faster onset of effect (within 30 minutes to several hours) 1, 2, 3

It is essential to establish appropriate expectations with the patient and family regarding the probability of a gradual response that develops over time, as informed by the American Academy of Child and Adolescent Psychiatry 1, 2
Patients should be informed that they should not expect immediate improvement, as occurs with stimulants, according to the American Academy of Child and Adolescent Psychiatry 1, 2

The daily dose of atomoxetine may be divided into two equal doses (morning and evening) to reduce adverse effects, as recommended by the American Academy of Child and Adolescent Psychiatry 1, 2
If necessary, it can be administered only at night, according to the American Academy of Child and Adolescent Psychiatry 1, 2
Titration should follow a sequential approach based on weight, with a maximum recommended dose of 1.4 mg/kg/day or 100 mg/day, whichever is lower, as informed by the American Academy of Child and Adolescent Psychiatry 4

Approximately 7% of the population are slow metabolizers (CYP2D6), with significantly higher plasma levels and longer half-life, which can lead to increased adverse effects, according to the American Academy of Pediatrics 4
The American Academy of Pediatrics recommends against increasing the dose too rapidly, as initial somnolence and gastrointestinal symptoms may occur if the dose is increased too quickly 5