What is the equivalent dose of Focalin XR (dexmethylphenidate) for a patient taking Mydayis (amphetamine and dextroamphetamine) 37.5 mg/day?

Equivalent Dose Conversion: Mydayis 37.5 mg to Focalin XR

For a patient taking Mydayis 37.5 mg/day, the equivalent starting dose of Focalin XR (dexmethylphenidate) is approximately 30-40 mg/day, divided into morning and early afternoon doses, recognizing that direct dose equivalence between amphetamine and methylphenidate classes is imprecise and requires clinical titration.

Rationale for Dose Conversion

Understanding the Medication Classes

• Mydayis contains mixed amphetamine salts (75% dextroamphetamine, 25% levoamphetamine) in a triple-bead extended-release formulation providing up to 16 hours of coverage 1
• Focalin XR contains only the d-threo enantiomer of methylphenidate (dexmethylphenidate), which is the pharmacologically active isomer, providing approximately 8-12 hours of coverage 1
• Amphetamines and methylphenidate work through different mechanisms: amphetamines act as substrates for monoamine transporters causing neurotransmitter release, while methylphenidate primarily blocks reuptake 2

Approximate Conversion Ratio

• The traditional conversion ratio suggests that methylphenidate is roughly half as potent as amphetamine on a milligram-per-milligram basis, meaning 2 mg methylphenidate ≈ 1 mg amphetamine 3
• Using this ratio, Mydayis 37.5 mg would convert to approximately 75 mg of methylphenidate equivalents 3
• However, because Focalin XR contains only the active d-isomer (versus racemic methylphenidate which is 50% active), the required dose is roughly half that of standard methylphenidate 4
• This yields an approximate Focalin XR equivalent of 30-40 mg/day 3, 1

Recommended Conversion Strategy

Initial Dosing Approach

• Start with Focalin XR 20 mg in the morning, with reassessment after 1 week 3
• If inadequate symptom control throughout the day, increase to 30 mg once daily in the morning 3
• Maximum FDA-approved dose for Focalin XR is 40 mg/day, which can be given as a single morning dose or split into morning and early afternoon doses 3

Titration Schedule

• Increase dose by 10 mg increments weekly as needed for symptom control 3
• Monitor for both efficacy (ADHD symptom control) and tolerability (appetite, sleep, cardiovascular effects) at each dose adjustment 3
• Target the lowest effective dose that provides adequate symptom coverage 3

Critical Considerations When Switching

Duration of Action Mismatch

• Mydayis provides 16 hours of coverage, while Focalin XR provides only 8-12 hours 1
• Patients may experience afternoon/evening symptom breakthrough when switching from Mydayis to Focalin XR 1
• Consider adding a late-afternoon immediate-release dexmethylphenidate 5-10 mg dose (no later than 2:00 PM) if evening coverage is needed 3

Side Effect Profile Differences

• Amphetamines (Mydayis) cause significantly more appetite suppression and sleep disruption compared to methylphenidate formulations 5
• Methylphenidate causes less insomnia, irritability, emotional lability, and anxiety compared to dextroamphetamine 5
• Patients switching from amphetamines to methylphenidate may experience improved sleep and appetite 3, 5

No Cross-Taper Required

• When switching between stimulant classes, cross-tapering is unnecessary 1
• Discontinue Mydayis and start Focalin XR the following morning 1
• Monitor closely during the first week for both symptom control and withdrawal/rebound effects 3, 1

Monitoring Parameters

First Week After Switching

• Assess ADHD symptom control using standardized rating scales (parent/teacher reports for children, self-report for adults) 3
• Monitor blood pressure and heart rate at baseline and weekly during titration 3
• Evaluate sleep quality, appetite, and weight 3, 5
• Document timing of symptom breakthrough to guide dosing adjustments 3

Ongoing Maintenance

• Monthly follow-up visits until symptoms stabilized on optimal dose 3
• Quarterly blood pressure and pulse checks once stable 3
• Regular assessment for emergence of tics, mood changes, or cardiovascular symptoms 3

Common Pitfalls to Avoid

• Assuming 1:1 dose equivalence between Mydayis and Focalin XR will lead to underdosing 3, 1
• Failing to account for the shorter duration of Focalin XR compared to Mydayis will result in evening symptom breakthrough 1
• Not monitoring for improved sleep and appetite when switching from amphetamines to methylphenidate misses important tolerability benefits 5
• Scheduling any methylphenidate dose after 2:00 PM increases insomnia risk 3
• Abandoning stimulants entirely if initial Focalin XR dose is inadequate, rather than properly titrating upward 3, 6