No, Do Not Increase the Dose Yet
You must wait a minimum of 3 days from initiation before increasing the atomoxetine dose from 40 mg. 111 Since the patient started only 2 days ago, it is too early to titrate.
FDA-Mandated Dosing Timeline
The FDA label for Strattera is explicit and unambiguous about the titration schedule:
- Initial dose: 40 mg daily (for patients >70 kg or adults)
- Minimum waiting period: 3 days before any dose increase
- Target dose: 80 mg daily after the minimum 3-day period
- Further increases: After 2-4 additional weeks at 80 mg, may increase to maximum 100 mg if response is suboptimal 111
Why This Waiting Period Matters
The 3-day minimum exists to assess tolerability, particularly for gastrointestinal side effects (nausea, abdominal pain) and initial somnolence, which are significantly more common when the dose is increased too rapidly 2. Rushing titration increases the risk of treatment discontinuation due to adverse events.
What to Do Tomorrow (Day 3)
On day 3, you can increase to 80 mg daily (the target dose), administered either:
Common Pitfall to Avoid
Do not judge efficacy at this early stage. Atomoxetine has an incremental response trajectory extending up to 24 weeks, with meaningful improvement often not apparent until 4-6 weeks at target dose 34. The most frequent dosing error in clinical practice is premature discontinuation or underdosing—real-world data show average adult doses of only ~60 mg/day despite the 80 mg target 3.
Keep the patient at 80 mg for at least 4 weeks before assessing whether further dose adjustment to 100 mg is needed 13.