Dose Equivalency Between Adderall XR 20mg and Strattera
There is no direct dose equivalency between Adderall XR 20mg and Strattera (atomoxetine) because they are fundamentally different medication classes with distinct mechanisms of action, pharmacokinetics, and efficacy profiles. 1, 2
Why Direct Conversion Is Not Possible
Atomoxetine is significantly less effective than amphetamine-based stimulants like Adderall XR, making any "equivalent" dose inherently problematic. 2 Research demonstrates that atomoxetine has medium-range effect sizes of approximately 0.7 compared to stimulants, and is explicitly positioned as second-line treatment after stimulant failure or contraindication. 3
- Adderall XR works within hours to days, while atomoxetine requires 6-12 weeks to achieve full therapeutic effect. 1, 3
- Stimulants achieve 70-80% response rates when properly titrated, whereas atomoxetine shows lower response rates. 4, 3
- Atomoxetine was significantly less effective than extended-release mixed amphetamine salts in head-to-head trials. 2
Standard Atomoxetine Dosing Protocol
If switching from Adderall XR 20mg to atomoxetine, start with the standard atomoxetine dosing protocol rather than attempting dose equivalency:
- Starting dose: 40 mg once daily for adults and patients over 70 kg. 1, 3
- Titration schedule: Maintain initial dose for minimum 7-14 days, then increase to 60 mg daily after 1 week, then 80 mg daily. 1, 3
- Target dose: 80 mg/day for adults over 70 kg (the recommended target despite real-world underdosing at ~60 mg/day). 1, 5
- Maximum dose: Lesser of 1.4 mg/kg/day or 100 mg/day. 1, 3
Critical Transition Considerations
When transitioning from Adderall XR to atomoxetine, use a cross-taper approach to maintain symptom control during the 6-12 week atomoxetine onset period:
- Start atomoxetine 0.5 mg/kg/day (approximately 40 mg) while continuing full-dose Adderall XR for 1 week. 6
- Week 2: Increase atomoxetine to 1.2 mg/kg/day (approximately 80 mg) while reducing Adderall XR to half-dose. 6
- Week 3 onward: Continue atomoxetine monotherapy at 80-100 mg/day. 6
- Maintain target dose for 4-6 weeks minimum before judging efficacy. 1, 5
Setting Appropriate Expectations
Patients must understand that atomoxetine will not provide the same degree or rapidity of symptom control as Adderall XR. 1, 3
- Expect gradual improvement over 6-12 weeks rather than immediate effect. 1, 3
- Approximately 43% of methylphenidate non-responders subsequently responded to atomoxetine, suggesting variable individual response. 1
- Common adverse effects include nausea, vomiting, fatigue, decreased appetite, abdominal pain, and somnolence. 1
When Atomoxetine Is Appropriate
Consider atomoxetine over continuing Adderall XR only in specific clinical scenarios:
- Substance abuse history or concerns about stimulant diversion (atomoxetine is uncontrolled). 3, 2
- Comorbid anxiety disorders (atomoxetine may be better tolerated). 3, 2
- Comorbid tics or Tourette syndrome. 2
- Patient preference to avoid controlled substances. 2
- Intolerable stimulant side effects despite trials of multiple stimulant formulations. 1, 3
Monitoring During Transition
- Obtain baseline and monitor blood pressure, heart rate, height, and weight at follow-up visits. 1
- Monitor closely for suicidal ideation, especially during first few months or dose changes (FDA black box warning). 1, 2
- Use standardized ADHD rating scales to track symptom response throughout the 6-12 week titration period. 3