Comparing Potency: Vyvanse vs Adderall
Neither medication is inherently "stronger" than the other—they have different potency ratios requiring dose adjustments when converting between them, with approximately 2.5 mg of Vyvanse being equivalent to 1 mg of Adderall. 1
Understanding the Potency Relationship
Conversion Ratios
- A 2.5:1 conversion factor (Vyvanse:Adderall) is used clinically, meaning 20 mg of Adderall converts to approximately 50 mg of Vyvanse 1
- When switching from Adderall XR 30 mg to Vyvanse, the recommended starting dose is 50 mg once daily, representing a conservative 1:1.67 conversion ratio that accounts for Vyvanse's prodrug metabolism 2
- This conversion ratio does not mean one drug is "stronger"—it reflects differences in their pharmacokinetic profiles and how they are metabolized 2
Pharmacological Differences That Affect Perceived Strength
Duration of Action:
- Vyvanse has a longer duration of effect (13-14 hours) compared to immediate-release Adderall, which may create the impression of greater strength due to sustained symptom control 3
- Adderall's effects typically wear off after 4-5 hours for immediate-release formulations, requiring multiple daily doses 4
- Vyvanse maintains consistent plasma concentrations throughout the day due to its prodrug mechanism 3
Mechanism of Action:
- Vyvanse (lisdexamfetamine) is a prodrug that must be enzymatically hydrolyzed in the blood to its active form, d-amphetamine 5, 3
- Adderall contains a mixture of amphetamine salts (75% dextroamphetamine and 25% levoamphetamine) that are immediately active 4
- Both ultimately increase dopamine and noradrenaline in the synaptic cleft through transporter inhibition 5
Clinical Efficacy Comparisons
Head-to-Head Evidence
- Direct comparison studies show Adderall had a small but statistically significant advantage over standard-release methylphenidate, with the strongest effects seen in global ratings 6
- No parallel-group, head-to-head trials directly compare Vyvanse to Adderall, making definitive superiority claims impossible 3
- Both medications demonstrate robust clinical efficacy with large effect sizes in treating ADHD core symptoms 3
Practical Clinical Considerations
- The lower dose of Adderall (7.5 mg) produced effects comparable to higher-dose Ritalin (17.5 mg), suggesting functional potency varies by specific dose comparisons 4
- Adderall was superior to lower-dose Ritalin when effects wore off at midday and late afternoon/early evening 4
- Vyvanse's prodrug formulation provides more consistent symptom control throughout the day without the midday "wearing off" phenomenon 3
Dosing Parameters
Maximum Approved Doses:
- Vyvanse: 70 mg daily maximum, started at 20-30 mg with 10 mg weekly increments 7, 1
- Adderall: 50 mg daily maximum, started at 10 mg with 5 mg weekly increments 7
Common Pitfall: Clinicians sometimes assume higher milligram amounts mean greater strength, but the 2.5:1 conversion ratio demonstrates this is not the case—50 mg of Vyvanse is therapeutically equivalent to 20 mg of Adderall 1
Side Effect Profiles
- Both medications produce comparable levels of clinically significant side effects 4
- Most common adverse events include decreased appetite, insomnia, dry mouth, headache, and irritability—typically mild to moderate and transient 3, 8
- Side effect profiles are consistent with CNS stimulant class effects regardless of which medication is used 3