Atomoxetine Dosing for a 90kg Adult Male with ADHD
Start atomoxetine at 40 mg once daily, then increase after a minimum of 3 days to the target dose of 80 mg daily, with the option to escalate to a maximum of 100 mg daily after 2-4 additional weeks if response is suboptimal. 1
Initial Dosing Protocol
- Begin with 40 mg once daily for adults and adolescents over 70 kg 1
- This starting dose applies regardless of the patient's specific weight above 70 kg 1
- The medication can be taken with or without food 1
- Administer as either a single morning dose or split into evenly divided doses (morning and late afternoon/early evening) 1
Dose Escalation Strategy
- After a minimum of 3 days, increase to the target dose of 80 mg daily 1
- If inadequate response after 2-4 additional weeks at 80 mg, escalate to the maximum dose of 100 mg daily 1
- No data support increased effectiveness at doses higher than 100 mg 1
- Clinical trials in adults used doses of 60,90, or 120 mg/day, though 120 mg exceeds current FDA-approved maximum 2, 3
Important Dosing Modifications
CYP2D6 considerations are critical for this patient:
- If the patient is taking strong CYP2D6 inhibitors (paroxetine, fluoxetine, quinidine), maintain the 40 mg starting dose for at least 4 weeks before increasing to 80 mg, and only if symptoms fail to improve and the initial dose is well tolerated 1
- Approximately 7% of the population are CYP2D6 poor metabolizers who require the same cautious dose escalation 4, 1
- CYP2D6 status significantly affects drug levels and side effect profile 4
Safety Monitoring Requirements
Before initiating treatment:
- Screen for personal or family history of bipolar disorder, mania, or hypomania 1
During treatment, monitor:
- Heart rate and blood pressure (modest increases are common but generally well tolerated) 4, 2
- Suicidality, clinical worsening, and unusual behavioral changes, especially during the first few months or at dose changes 4
- Common adverse effects include dry mouth, insomnia, nausea, decreased appetite, constipation, dizziness, sweating, dysuria, sexual problems, and palpitations 2, 3
Clinical Pearls
- Atomoxetine can be discontinued without tapering 1
- Capsules must be swallowed whole and should not be opened 1
- The drug carries negligible abuse potential and is not a controlled substance, making it particularly useful for patients at risk for substance abuse 2, 3
- Response rates in adult trials showed 28-30% mean reduction in ADHD symptom scores versus 18-20% with placebo 2, 3
- Withdrawal rates due to adverse events in adult trials ranged from 7.8-9.3% versus 2.4-4.3% with placebo 2, 3