Equivalent Dosing: Adderall IR 10mg Twice Daily to Adderall XR
For an adult taking Adderall IR 10mg twice daily (total 20mg/day), the equivalent dose is Adderall XR 20mg once daily in the morning. 1, 2
Bioequivalence Evidence
Adderall XR 20mg once daily is bioequivalent to Adderall IR 10mg twice daily in both rate and extent of drug absorption for both d-amphetamine and l-amphetamine. 3, 4
- Pharmacokinetic studies demonstrate that a single 20mg dose of Adderall XR produces comparable plasma concentration profiles to two 10mg doses of immediate-release Adderall given 4 hours apart 3
- The extended-release formulation contains immediate-release beads that deliver the first 10mg upon ingestion, and delayed-release beads that release the second 10mg approximately 4 hours later, mimicking twice-daily dosing 4, 5
- Maximum plasma concentration (Cmax) and area under the curve (AUC) values are statistically equivalent between the two formulations 3
Duration of Action
- Adderall XR provides approximately 12 hours of symptom coverage from a single morning dose, compared to 8-10 hours total from twice-daily immediate-release dosing 4, 5
- Onset of action occurs within 1.5 hours, similar to immediate-release formulations 4
- A single morning dose of Adderall (at equivalent total daily dose) produces behavioral effects throughout an entire school/work day that are equivalent to standard twice-daily methylphenidate dosing 6
Administration Considerations
- Adderall XR should be taken once daily in the morning to minimize sleep disturbances 1, 2
- The capsule can be swallowed whole or opened and sprinkled on applesauce without affecting bioavailability—both fasted and fed states show equivalent absorption 3
- Once-daily dosing improves medication adherence by eliminating the need for midday doses and reduces potential for diversion 2
Titration After Conversion
- After converting to Adderall XR 20mg, allow at least one week to evaluate response before making further dose adjustments 1, 2
- If additional titration is needed, increase by 5mg weekly increments based on clinical response and tolerability 1
- The maximum recommended daily dose is 40-50mg for adults, though some patients may require up to 60mg with clear documentation 1, 7
Monitoring Parameters
- Check blood pressure and pulse at baseline and with each dose adjustment 1, 2
- Monitor for common side effects including appetite suppression, insomnia, and weight changes 1, 2
- Obtain weekly symptom ratings during any dose adjustments to assess therapeutic response 1
Common Pitfall to Avoid
Do not assume the patient needs a higher total daily dose simply because they are switching formulations—the 1:1 conversion (20mg IR total = 20mg XR) is pharmacokinetically validated and should be the starting point 3, 4. Only increase the dose if ADHD symptoms remain inadequately controlled after at least one week on the equivalent XR dose 1.