Mydayis and Vyvanse are both once-daily amphetamine stimulants for ADHD, but they get their long duration two completely different ways: Mydayis uses a triple-bead delayed-release capsule, while Vyvanse relies on a prodrug that only becomes active after the body converts it. This guide compares how each delivers extended coverage, age approvals, dosing, and side effects.
This is general information, not medical advice. Both are Schedule II controlled substances.
Mydayis vs Vyvanse at a glance
| Mydayis (mixed amphetamine salts) | Vyvanse (lisdexamfetamine) | |
|---|---|---|
| Active drug | Same 3:1 dextro/levo-amphetamine mix as Adderall XR | Prodrug converted to dextroamphetamine |
| Delivery mechanism | Three-bead capsule (immediate + two delayed-release beads) | Prodrug conversion (gradual, not a mechanical release) |
| Duration | Up to 16 hours | Up to about 13-14 hours |
| FDA-approved for | ADHD (ages 13+) | ADHD (ages 6+), binge eating disorder (adults) |
| Initial US approval | 2017 | 2007 |
| Schedule | II | II |
What each is approved for
Mydayis is indicated for ADHD in patients 13 years and older. The label explicitly states it is not approved for children 12 and younger; an FDA review of pediatric studies in the 6-to-12 age group found it was not apparent that the lowest effective dose had been clearly identified in that younger population, which is part of why the approval stayed limited to teens and adults.
Vyvanse covers a broader age range for ADHD (6 and older) and carries the additional binge eating disorder indication in adults that Mydayis does not have.
How the two achieve long duration differently
Mydayis is built from three types of drug-releasing beads in a 1:1:1 ratio inside one capsule: one bead releases the amphetamine salts immediately after swallowing, and the other two are formulated to dissolve later, one in the stomach and one further down in the intestine. This staggered mechanical release is what stretches a single morning dose out to roughly 16 hours, the longest duration among common single-dose amphetamine ADHD products at the time of its approval.
Vyvanse contains lisdexamfetamine, which the label describes as inactive until enzymatically converted in the body into active dextroamphetamine. There’s no bead or coating involved; the gradual appearance of the active drug in the bloodstream comes from the rate-limited conversion process itself, which happens to produce a duration profile of roughly 13 to 14 hours for many patients, slightly shorter than Mydayis’s stated up-to-16-hour window.
Dosing
Mydayis capsules come in 12.5 mg, 25 mg, 37.5 mg, and 50 mg strengths, taken once daily in the morning upon waking. The label specifically warns against substituting Mydayis for Adderall XR on a milligram-per-milligram basis, despite containing the same four amphetamine salts, because the different release mechanisms give the two products different pharmacokinetic profiles even at a nominally equal dose.
Vyvanse is dosed once daily as well, starting at 30 mg for ADHD and titrating in 10 or 20 mg increments up to a maximum of 70 mg per day. For patients with severe renal impairment, the Vyvanse label caps the dose at 50 mg/day, and at 30 mg/day for end-stage renal disease.
Side effects
Both share the standard amphetamine-class side-effect profile: decreased appetite, insomnia, dry mouth, increased heart rate, and anxiety or jitteriness. Because Mydayis is intended to still be active well into the evening (up to 16 hours after a morning dose), some patients find its late-day stimulant effect makes falling asleep at a normal bedtime harder than with a shorter-acting product, a tradeoff directly tied to the extended duration that is its main selling point.
Who each might suit
Factors that may point toward Mydayis:
- A need for coverage that extends meaningfully into the evening (homework, driving, work commitments past a typical 12-hour stimulant window)
- Being 13 or older, since it is not approved for younger children
- Prior good response to Adderall’s amphetamine salt combination, with a need for a longer duration than Adderall XR provides
Factors that may point toward Vyvanse:
- Needing ADHD coverage starting at a younger age (6 and up)
- A co-occurring binge eating disorder diagnosis
- A preference for a drug whose reduced non-oral misuse appeal comes from its prodrug chemistry rather than a mechanical bead release, which can still theoretically be defeated by opening the capsule in certain ways
Frequently asked questions
Can Mydayis be substituted for Adderall XR at the same dose?
No. The label specifically warns against milligram-per-milligram substitution because Mydayis’s three-bead release mechanism gives it a different pharmacokinetic profile than Adderall XR, even with the same active salts.
Why isn’t Mydayis approved for children under 13?
FDA review of studies in children 6 to 12 found it was not apparent that the lowest effective dose had been clearly established in that age group, so the approval stayed limited to patients 13 and older.
Which lasts longer, Mydayis or Vyvanse?
Mydayis is described as lasting up to about 16 hours; Vyvanse’s effect is generally described as lasting around 13 to 14 hours for many patients. Individual response varies.
Does Vyvanse treat anything besides ADHD?
Yes, it’s also approved for moderate to severe binge eating disorder in adults. Mydayis has no comparable additional indication.
Are both controlled substances?
Yes, both are Schedule II under federal law.
Practical tips for either drug
- Take both first thing in the morning; because Mydayis can remain active up to 16 hours, a late morning dose risks pushing insomnia well past a reasonable bedtime.
- Don’t assume a Mydayis and Adderall XR dose in the same milligram number will feel the same; the label explicitly warns against that substitution given the different release mechanisms.
- Watch for appetite dips through the school or work day with either drug; a bigger breakfast before dosing and a substantial dinner once the effect fades helps offset lost midday calorie intake, especially in growing children.
- Keep either medication locked and tracked; both are Schedule II with documented abuse potential, and household misuse (by siblings, roommates, etc.) is a real, common concern flagged across amphetamine labels.
- Report any new chest pain, fainting, or shortness of breath immediately; both labels warn about sudden death risk in patients with underlying structural heart problems.
How insurance and cost typically compare
Both Mydayis and Vyvanse are generally more expensive brand-name options relative to generic mixed amphetamine salts or generic methylphenidate products, since as of recent years lisdexamfetamine (generic Vyvanse) has become more widely available, typically lowering its cost compared with brand Mydayis, which has fewer generic alternatives given its more complex three-bead delivery system. Insurance formularies often require a prior authorization or a documented trial of a cheaper stimulant first before covering either, a common utilization-management step across newer or more complex extended-release stimulant products.
Frequently asked questions (continued)
Is Mydayis more expensive than Vyvanse?
Generic lisdexamfetamine (generic Vyvanse) is often more widely available and less costly than Mydayis, which has fewer generic equivalents given its three-bead delivery system; actual cost depends heavily on insurance coverage and pharmacy.
Can I open a Mydayis capsule and sprinkle the beads on food?
Follow the specific instructions in the Mydayis label and consult the pharmacist; not all extended-release stimulant capsules are approved for this, and doing so without label support could alter the intended release profile.
Does either drug interact with antacids or stomach acid reducers?
Because Mydayis relies on beads designed to dissolve at different points in the digestive tract, changes in stomach pH from acid-reducing medications could theoretically affect its release pattern; discuss any acid reducer use with the prescriber.
References
- FDA. VYVANSE (lisdexamfetamine dimesylate) prescribing information.
- DailyMed. MYDAYIS (mixed salts of a single-entity amphetamine product) extended-release capsules, prescribing information.
- FDA. Mydayis pediatric labeling supplement approval letter (2019).
- Psychiatric News. FDA Approves Once-Daily ADHD Medication for Adults (2017).
- Medscape. FDA Clears Long-Acting ADHD Drug Mydayis (2017).