From the FDA Drug Label
The extent of bioavailability of the sustained-release capsule was similar compared to the immediate-release tablet. Following administration of three 5 mg tablets, average maximal dextroamphetamine plasma concentrations (Cmax) of 36. 6 ng/mL were achieved at approximately 3 hours. Following administration of one 15 mg sustained-release capsule, maximal dextroamphetamine plasma concentrations were obtained approximately 8 hours after dosing.
To convert Adderall XR to IR, the key concept is that the extent of bioavailability of the sustained-release capsule is similar to the immediate-release tablet.
- The dosage of the sustained-release capsule is higher than the immediate-release tablet, with one 15 mg sustained-release capsule being compared to three 5 mg tablets.
- The time to maximal concentration is different, with the IR tablets reaching maximal concentration at approximately 3 hours and the XR capsule at approximately 8 hours. Based on the information provided, the conversion can be considered as a 1:1 ratio in terms of dosage, but the frequency of administration will need to be adjusted due to the difference in time to maximal concentration, with the IR tablets typically administered more frequently than the XR capsule 1.
From the Research
When converting from Adderall XR to Adderall IR, the total daily dose typically remains the same, but is divided into multiple doses throughout the day, with careful consideration of the potential increased risk of adverse cardiovascular events, as evidenced by the increased blood pressure and heart rate associated with amphetamine use 2.
Key Considerations
- The conversion should maintain the same total daily amphetamine exposure while accounting for the different release mechanisms of XR and IR formulations.
- Patients should take their first IR dose in the morning and subsequent doses no later than mid-afternoon to avoid sleep disruption.
- The dosing schedule should be supervised by a healthcare provider who can adjust the schedule based on individual response, tolerance, and specific needs.
- Monitoring for side effects during this transition is crucial, including changes in heart rate, blood pressure, appetite, or sleep patterns, as amphetamines have been associated with increased blood pressure, heart rate, and withdrawals due to adverse effects 2.
Dosing Example
For example, if a patient takes 20mg of Adderall XR once daily, they would typically convert to 10mg of Adderall IR taken twice daily, with doses separated by 4-6 hours.
Important Factors
- The pharmacokinetic properties of long-acting stimulant formulations, including the rate and extent of absorption, variability, dose proportionality, bioequivalence, and potential for accumulation, should be considered when selecting a long-acting stimulant 3.
- Certain factors, such as individual variability in pharmacokinetics, can contribute to increased variability in outcomes and potentially affect the efficacy and safety of the medication.