What is the recommended starting dose of dextroamphetamine (versus amphetamine salts) for a patient with Attention Deficit Hyperactivity Disorder (ADHD) or narcolepsy, with no significant medical history?

Starting Dose Recommendations: Dextroamphetamine vs Amphetamine Salts

For ADHD, start dextroamphetamine at 5 mg once or twice daily in patients ≥6 years old, or 2.5 mg daily in children 3-5 years; for narcolepsy, start dextroamphetamine at 10 mg daily in patients ≥12 years or 5 mg daily in ages 6-12, with both conditions requiring weekly titration in 5-10 mg increments until optimal response. 1

ADHD Treatment Dosing

Dextroamphetamine Starting Doses

• Children 3-5 years: Start at 2.5 mg daily, increase by 2.5 mg weekly until optimal response 1
• Children ≥6 years and adults: Start at 5 mg once or twice daily, increase by 5 mg weekly until optimal response 1
• Maximum dose rarely exceeds 40 mg/day total 1
• Administer first dose upon awakening, with additional doses (1-2) at 4-6 hour intervals 1

Mixed Amphetamine Salts (Adderall XR) Starting Doses

• Standard starting dose: 10 mg once daily in the morning 2
• Titration: Increase by 5 mg weekly increments up to maximum of 50 mg daily 2
• Extended-release formulation provides approximately 8-9 hours of coverage 3

Key Differences in ADHD Dosing

The FDA label for dextroamphetamine provides more granular age-based dosing compared to mixed amphetamine salts, with dextroamphetamine approved for children as young as 3 years (starting at 2.5 mg), while mixed amphetamine salts typically start at 10 mg for older children and adults 1, 2. Both medications demonstrate equivalent efficacy for ADHD core symptoms, with response rates approaching 93-100% when appropriately dosed 4, 5.

Narcolepsy Treatment Dosing

Dextroamphetamine for Narcolepsy

• Ages 6-12 years: Start at 5 mg daily, increase by 5 mg weekly until optimal response 1
• Ages ≥12 years and adults: Start at 10 mg daily, increase by 10 mg weekly until optimal response 1
• Typical therapeutic range: 5-60 mg/day in divided doses 1
• Evidence-based dosing: Studies demonstrate total daily doses of 60 mg for dextroamphetamine effectively reduce daytime sleepiness 2

Mixed Amphetamine Salts for Narcolepsy

The guidelines do not provide specific starting doses for mixed amphetamine salts in narcolepsy, though the American Academy of Child and Adolescent Psychiatry notes that dextroamphetamine, methylphenidate, and pemoline all significantly reduce daytime sleepiness at comparable doses 2.

Narcolepsy-Specific Considerations

Dextroamphetamine is conditionally recommended by the American Academy of Sleep Medicine for narcolepsy treatment, with clinically significant improvements in excessive daytime sleepiness and cataplexy, though common adverse effects include appetite loss, irritability, and weight loss 6, 7. The evidence quality is rated as very low, but clinical practice supports its use as an alternative to modafinil/armodafinil 8, 9.

Critical Implementation Details

Timing and Administration

• Avoid late evening doses to prevent insomnia 1
• Give first dose upon awakening 1
• Space additional doses 4-6 hours apart for immediate-release formulations 1
• Extended-release formulations should be given once daily in the morning 2

Titration Strategy

• Allow one week between dose increases to accurately assess response and side effects 1
• Reduce dose if bothersome adverse reactions appear (insomnia, anorexia) 1
• Monitor blood pressure, pulse, and weight at each dose adjustment 10
• Collect ADHD symptom ratings before each dose increase 10

Pre-Treatment Assessment

Before initiating either medication, assess for cardiac disease through careful history (including family history of sudden death or ventricular arrhythmia) and physical examination 1. Evaluate family history and clinically assess for motor/verbal tics or Tourette's syndrome 1.

Common Pitfalls to Avoid

• Starting too high: Beginning above recommended starting doses leads to unnecessary side effects and decreased adherence 10
• Inadequate titration time: Failing to allow one week between increases prevents accurate response assessment 10
• Missing side effect assessment: Not systematically evaluating for insomnia, appetite suppression, headaches, and cardiovascular effects at each visit 10
• Ignoring duration needs: Adults may require longer daily coverage than children; consider extended-release formulations for 8-12 hour coverage 3, 10
• Continuing escalation without benefit: If symptoms plateau at maximum dose, switch medication classes rather than exceeding recommendations 10

Evidence Quality Considerations

The FDA drug label 1 provides the most authoritative dosing guidance for dextroamphetamine, while guideline evidence for mixed amphetamine salts comes from the American College of Obstetrics and Gynecology 2. Both medications have demonstrated efficacy in reducing ADHD symptom severity, though the overall quality of evidence is rated as low to very low due to short study durations, restrictive inclusion criteria, and risk of bias from the subjective effects of amphetamines revealing treatment assignment 5.