Is 20 mg (Adderall) (amphetamine and dextroamphetamine) twice daily more common than 15 mg twice daily for an adult patient with Attention Deficit Hyperactivity Disorder (ADHD)?

Adderall Dosing in Adult ADHD: 20 mg BID vs 15 mg BID

20 mg twice daily is more common than 15 mg twice daily for adult ADHD treatment with Adderall (mixed amphetamine salts). The evidence consistently shows that 20 mg BID falls within the standard therapeutic range, while 15 mg BID is not a typical dosing increment used in clinical practice or research protocols.

Standard Dosing Patterns for Adult ADHD

The American Academy of Child and Adolescent Psychiatry recommends dextroamphetamine at a dosage of 5 mg three times daily to 20 mg twice daily for adults with ADHD 1. This establishes 20 mg BID as the upper end of the standard dosing range and a recognized therapeutic target.

Clinical trials consistently use 20 mg as a standard dose increment:

• Multiple studies initiated treatment at 20 mg/day with titration upward, establishing this as a foundational starting point 2
• The average effective dose in controlled trials was 54 mg/day administered in two daily doses, which translates to approximately 27 mg per dose—closer to 20-30 mg BID than 15 mg BID 3
• Long-term studies enrolled subjects starting at 20 mg/day for 1 week, with subsequent titration up to 60 mg/day 2

Why 15 mg BID Is Uncommon

15 mg twice daily does not align with standard tablet strengths or dosing increments. Adderall is manufactured in 5 mg, 10 mg, 15 mg, 20 mg, and 30 mg tablets. To achieve 15 mg BID, clinicians would need to prescribe either:

• One 15 mg tablet twice daily (which is actually a standard option)
• Three 5 mg tablets twice daily (unnecessarily complex)

However, the clinical trial literature and dosing guidelines do not reference 15 mg BID as a common therapeutic target. Instead, titration typically proceeds in 5-10 mg increments 4, moving from 10 mg BID to 20 mg BID, effectively skipping the 15 mg BID dose.

Evidence from Clinical Trials

Research demonstrates that lower doses are often subtherapeutic:

• One open-label study found a mean end dose for responders of only 10.77 mg/day (approximately 5 mg BID), but this represented a relatively low-dose approach with a 54% response rate 5
• In contrast, controlled trials using higher doses achieved 70% response rates with an average dose of 54 mg/day (approximately 27 mg BID) 3
• The most robust long-term data used a range of 20-60 mg/day, with no mention of 15 mg BID as a standard dose 2

Practical Dosing Algorithm

For adult ADHD, the typical titration follows this pattern:

1. Start at 5-10 mg once or twice daily 4, 1
2. Increase by 5-10 mg weekly based on response 4
3. Common therapeutic doses are 10 mg BID, 20 mg BID, or 30 mg BID
4. Maximum doses reach 40 mg for amphetamine salts in adults, though some patients may require up to 60-80 mg total daily dose 4, 1

The American Academy of Child and Adolescent Psychiatry explicitly recommends methylphenidate at 5 to 20 mg three times daily or dextroamphetamine at 5 mg three times daily to 20 mg twice daily, establishing 20 mg BID as a standard upper dosing target 1.

Clinical Considerations

20 mg BID represents a moderate-to-high therapeutic dose that is well-established in clinical practice:

• It falls within the 10-50 mg total daily dose range recommended for adults 1
• At 40 mg total daily dose, it provides robust symptom control for most patients
• It aligns with standard tablet strengths, simplifying prescribing and adherence

Common pitfall to avoid: Do not assume that 15 mg BID is a standard intermediate dose. The evidence supports titration in 5-10 mg increments, which naturally leads to 10 mg BID or 20 mg BID as therapeutic targets 4. If a patient requires a dose between these increments, consider 15 mg in the morning and 10 mg in the afternoon, or adjust timing rather than creating non-standard twice-daily dosing 4.