What is the difference between Dexedrine (Dextroamphetamine) and Adderall IR (Amphetamine) in terms of dosing and duration of action?

Dexedrine vs Adderall IR: Key Differences

Dexedrine (dextroamphetamine) contains only the dextro-isomer of amphetamine, while Adderall IR contains a 3:1 ratio of dextroamphetamine to levoamphetamine, making Adderall slightly more potent per milligram with potentially broader receptor activity. 1

Composition Differences

• Dexedrine is pure dextroamphetamine, the more pharmacologically active isomer 2
• Adderall IR contains mixed amphetamine salts in a 3:1 ratio of dextroamphetamine to levoamphetamine, providing effects at both α- and β-adrenergic receptor sites 1, 3

Dosing Recommendations

Starting Doses

• Dexedrine IR: Start at 5 mg twice daily 2
• Adderall IR: Start at 5 mg once or twice daily, though the extended-release formulation (Adderall XR) typically starts at 10 mg once daily 4, 2

Titration Strategy

• Both medications should be titrated in 5 mg increments 5, 4
• Allow at least one week between dose increases to properly evaluate response 4
• Maximum recommended daily dose for both is 40-50 mg 5, 4

Duration of Action

• Dexedrine IR: Approximately 4-6 hours per dose, requiring twice-daily dosing 2
• Adderall IR: Approximately 4-6 hours per dose, similar to Dexedrine IR 1
• Adderall XR (for comparison): 12-hour duration with rapid onset within 1.5 hours, using a bimodal delivery system that releases half the dose immediately and half after 4 hours 6, 1

Clinical Efficacy Considerations

• Meta-analysis data suggests Adderall has a small but statistically significant advantage over standard methylphenidate, with the strongest effects seen in global ratings and clinician/parent assessments 7
• The mixed amphetamine composition in Adderall may provide more comprehensive norepinephrine release affecting both α- and β-adrenergic receptors compared to pure dextroamphetamine 3

Practical Prescribing Differences

Dosing Frequency

• Both immediate-release formulations typically require twice-daily dosing to maintain symptom control throughout the day 2
• Morning administration is critical for both to minimize sleep disturbances 4

Dose Equivalency

• Due to the 3:1 ratio in Adderall, some clinicians consider Dexedrine to require approximately half the dose of Adderall for equivalent effect, though this is not universally established 2

Common Pitfalls to Avoid

• Starting too high: Begin with the lowest recommended dose (5 mg) to minimize side effects and improve adherence 4
• Inadequate monitoring intervals: Rushing dose increases before allowing one week to evaluate response leads to unnecessary side effects 4
• Ignoring timing: Afternoon or evening doses of either medication will cause insomnia 4
• Exceeding maximum doses: When 40-50 mg daily is ineffective, switch to an alternative medication rather than continuing to escalate 4

Monitoring Requirements

• Check blood pressure and pulse at baseline and with each dose increase 4
• For adults on chronic stimulant therapy, monitor vital signs quarterly 4
• Assess weight at each visit due to appetite suppression effects 4
• Document clearly when prescribing above 40 mg that lower doses were inadequate 5