Duration of Action for Adderall IR
Adderall IR (immediate-release) provides clinical benefits for 3 to 5 hours after oral dosing in adults with ADHD. 1
Pharmacokinetic Profile
The immediate-release formulations of amphetamine-based stimulants, including Adderall IR, have a brief duration of action that necessitates multiple doses throughout the day to maintain symptom control. 1
Key timing characteristics:
- Onset of action: Effects begin within 30 minutes to 2 hours after ingestion 1
- Peak plasma concentration: Approximately 3 hours after dosing 2
- Duration of therapeutic effect: 3 to 5 hours 1
- Plasma half-life: Approximately 11-12 hours for dextroamphetamine 1, 2
Important Clinical Distinction
The therapeutic effects of amphetamine stimulants are concentrated within the absorption phase, meaning symptom control disappears well before the medication leaves the plasma. 1 This phenomenon explains why the clinical duration (3-5 hours) is substantially shorter than the plasma half-life (11-12 hours). 1, 2
Practical Dosing Implications
Due to the short duration of action, Adderall IR requires multiple daily doses (typically 2-3 times per day) to maintain improvement throughout the day for school, work, and after-school activities. 1
Common pitfall: Clinicians may mistakenly assume the 11-12 hour half-life translates to all-day coverage, but therapeutic effects end after only 3-5 hours, requiring additional doses for sustained symptom control. 1
Extended-Release Alternative
For patients requiring longer duration of coverage, Adderall XR provides 12 hours of symptom control with once-daily morning dosing, eliminating the need for multiple daily doses and in-school administration. 3, 4 The extended-release formulation uses a biphasic delivery system with immediate-release and delayed-release beads to achieve this prolonged effect. 5