What is the equivalent dose of 70 mg lisdexamfetamine (Vyvanse) in serdexmethylphenidate/dexmethylphenidate (Azstarys)?

Dose Equivalence: Vyvanse 70mg to Azstarys

There is no established direct dose equivalence between Vyvanse (lisdexamfetamine) 70mg and Azstarys (serdexmethylphenidate/dexmethylphenidate), as these are fundamentally different stimulant classes—amphetamine-based versus methylphenidate-based medications.

Understanding the Challenge

Converting between amphetamine and methylphenidate formulations is not straightforward because:

• Different mechanisms: While both block monoamine reuptake, they have distinct pharmacological profiles and individual patient responses vary significantly 1
• No validated conversion ratios exist: The evidence shows approximately 70% of patients respond to either methylphenidate or amphetamines alone, but nearly 90% respond if both classes are tried, indicating these are not interchangeable 2
• Individual variability: Response to stimulants is unpredictable and not dose-dependent in a linear fashion across medication classes 1

Practical Approach to Switching

When switching from Vyvanse 70mg to Azstarys, start with Azstarys 39.2/7.8 mg (equivalent to 30 mg dexmethylphenidate) and titrate based on clinical response.

Rationale for Starting Dose:

• Azstarys comes in three strengths: 26.1/5.2 mg, 39.2/7.8 mg, and 52.3/10.4 mg (equivalent to 20,30, and 40 mg dexmethylphenidate respectively) 3
• The middle dose (39.2/7.8 mg) provides a reasonable starting point when switching from a high-dose amphetamine formulation
• Azstarys provides 13-hour duration of action with rapid onset 4, comparable to Vyvanse's extended duration

Titration Strategy:

1. Week 1: Start Azstarys 39.2/7.8 mg once daily in the morning
2. Week 2-3: Assess response using ADHD rating scales and side effect monitoring
3. Adjust:
   • If inadequate response and tolerating well → increase to 52.3/10.4 mg
   • If excessive side effects → decrease to 26.1/5.2 mg
   • If optimal response → maintain current dose

Critical Monitoring Points:

Common side effects to monitor (more frequent with Azstarys than other methylphenidate formulations):

• Decreased appetite (62.4%)
• Insomnia (28.7%)
• Irritability/aggression (26.1%)
• Weight decrease (21.1%)
• Mood swings (13.9%) 5

Important caveats:

• Do not assume equivalent efficacy—methylphenidate may be more or less effective than amphetamines for this individual patient
• The 70mg Vyvanse dose suggests either high symptom severity or tolerance; be prepared that the patient may require the maximum Azstarys dose (52.3/10.4 mg)
• Monitor blood pressure and heart rate at each visit 3
• Assess for signs of abuse potential, though Azstarys' prodrug design may reduce this risk 3, 6

Growth monitoring in children: If switching a pediatric patient, monitor height and weight Z-scores, though changes are typically not clinically significant (mean Z-score changes of -0.20 for weight and -0.21 for height at 12 months) 7.