This PsychSnap was reviewed and updated December 2, 2025.
Gabriel is a 34 yo man with ADHD who has been stable on Adderall XR 30mg for 15 years. He can’t get the medication due to a shortage at the pharmacy. What else can you prescribe if Adderall XR is not available?
There are only two types of stimulants that are prescribed for ADHD – methylphenidate derivatives and amphetamine derivatives. These are different medications with different mechanisms of action. The 25+ stimulant pills, liquids, and patches that are available are sophisticated delivery systems that release methylphenidate or amphetamine derivatives at different speeds and for different durations. The immediate release formulations of methylphenidate (duration of 3-4 hours) and amphetamine (duration of 4-6 hours) both need to be dosed 2-3 times a day. Some longer acting formulations only need to be dosed once daily.
For a frequently updated, reliable guide to ADHD medications, see adhdmedicationguide.com. Currently, there are 16 formulations of methylphenidate, 13 formulations of amphetamines, and 5 non-stimulant medications for ADHD summarized in the 2-page handout.
All stimulants for ADHD are composed of varying amounts of the two enantiomers (dex/dextro (D) or levo (L)) of either methylphenidate or amphetamine. Both enantiomers of amphetamine are pharmacologically active, while only the d-enantiomer of methylphenidate is active. Amphetamines are approximately twice as potent as methylphenidate, meaning that Adderall (mixed amphetamine salts (75% D and 25% L amphetamine)) 10mg is roughly equivalent to methylphenidate 20mg.
For our patient who is taking Adderall XR 30mg daily:
The closest substitute for Adderall XR would be another amphetamine. Adderall XR 30mg has a double-pulsed release, with 50% (Adderall 15mg) released immediately, and 50% (Adderall 15mg) released 4 hours later. Adderall XR 30mg is essentially Adderall 15mg BID, if the second dose of the immediate release is taken 4 hours after the first dose. The XR pill is useful because people don’t need to remember to take a second dose of immediate-release at lunchtime.
The plasma level of a stimulant at a given time determines its clinical effect. If you want a stimulant to act for a longer period of time, the dose needs to be increased in proportion to the increased duration. To make the therapeutic effect of Adderall 15mg (which lasts 4-6 hours) last twice as long, you can prescribe Adderall 15mg BID (4 hours apart) or Adderall XR 30mg daily. You would not prescribe Adderall XR 15mg daily (which lasts 8-12 hours), because then the patient gets half the dose over twice the duration.
Psychotropic medications that are used in mood disorders do not require the same increase in dose based on an increased duration of action. In terms of therapeutic effect, venlafaxine 75mg is equivalent to venlafaxine XR 75mg and lithium 600mg is equivalent to lithium CR 600mg, though one form may be preferred due to side effects. The therapeutic benefits from lithium or antidepressants are due to downstream effects that occur over days to weeks.
If neither Adderall XR nor Adderall is available, there are newer and more expensive formulations of the same mixed amphetamine salts (75% D and 25% L). Adzenys XR is a long-acting, orally dissolving tablet with the same duration of action as Adderall XR. Adderall XR 30mg = Adzenys XR ODT 18.8mg due to differences in bioavailability.
Mydayis is a branded triple pulse release of Adderall. A third of the dose is released immediately, a third is released 4 hours later, and the last third is released 4 hours later. Taking Adderall XR 30mg in the morning and Adderall (immediate release) 15mg eight hours later produces plasma concentrations similar to Mydayis 45mg daily over 12-16 hours. The closest available Mydayis pill would be 50mg (vs 37.5mg).
If your head is spinning, that’s ok. The main point is that when your patients come to you on stimulant pills that you have never heard of before, you know that they are all derivatives of either amphetamine or methylphenidate, and that there are rational ways to switch between them within the class. You also know how to convert between Adderall XR and Adderall. Take a look at the summary table below to help with these conversions, and then we’ll cover Vyvanse and d-amphetamine.
Conversions between common amphetamine derivatives for treating ADHD
| Adderall | Adderall XR | Adzenys XR-ODT | Mydayis XR | Dextro-amphetamine | Dexedrine Spansules (ER) | Vyvanse (lisdexam-fetamine) | |
| Duration per dose | 4-6 h | 8-12 h | 8-12 h | 12-16 h | 4-6 h | 6-8 h | 10-14 h |
| Enantiomers | 75% D, 25% L | 75% D, 25% L | 75% D, 25% L | 75% D, 25% L | 100% D | 100% D | prodrug-> 100%D |
| Dose equivalence (approximate) | 5mg BID | 10mg | 6.3mg | 15mg | 4mg BID | 8mg | 26mg |
| Conversion Factor from Adderall XR (total dose) | 1 | 1 | Adderall x0.63 | Adderall x1.5 | Adderall x0.83 | Adderall x0.83 | Adderall x2.6 |
| Pill doses available (in mg) | 5, 7.5, 10, 12.5, 15, 20, 30 | 5, 10, 15, 20, 25, 30 | 3.1, 6.3, 9.4, 12.5, 15.7, 18.8 | 12.5, 25, 37.5, 50 | 5, 10 | 5, 10, 15 | 10, 20, 30, 40, 50, 60, 70 |
| Cost | $ | $ | $$$$ | $$$ | $ | $ | $$ |
Vyvanse (now generic!) is the brand name of lisdexamfetamine. While Adderall is composed of mixed amphetamine salts (75% D, 25% L), Vyvanse is a prodrug that is converted to 100% D-amphetamine. The molecule lisdexamfetamine (using the British spelling dexamfetamine) is d-amphetamine covalently bonded to L-lysine. It cannot cross the blood brain barrier. Put another way, if one were to crush and snort Vyvanse, there would be no euphoric effect. The same is not true for Adderall. When taken by mouth, Vyvanse is absorbed in the gut and hydrolyzed by red blood cells, releasing the pharmacologically active d-amphetamine molecule slowly over ~12 hours.
In addition to being longer-acting, Vyvanse is often experienced as being smoother, with fewer and more gradual ups and downs than Adderall XR. Adderall XR 30mg is (very) approximately Vyvanse 78mg. Rounding the Vyvanse dose to the closest available pill produces a dose ‘equivalence” of Vyvanse 70mg daily. Vyvanse at higher doses also has an FDA indication for binge eating disorder.
D-amphetamine is also available generically as immediate release dextroamphetamine (also called Dexedrine, Dextrostat), and dexedrine spansules (an extended release capsule). These medications could also be used as substitutes for Adderall. D-amphetamine is slightly more potent than Adderall with a similar duration of action.
Let’s return to Gabriel who can’t fill the Adderall XR 30mg prescription that has helped him throughout his adult life. If we learn from the pharmacist which stimulants in the same class (methylphenidate or amphetamine derivatives) are available, we can pick a reasonable substitute. If only specific doses of immediate release Adderall or dextroamphetamine are available, they can also be split or combined as necessary. Longer acting formulations should not be split.
Key Points
- There are two types of stimulants that are prescribed for ADHD – methylphenidate derivatives and amphetamine derivatives.
- To extend the duration of action of a stimulant, increase the dose in proportion to the increased duration. If you want Adderall 10mg to last twice as long, prescribe Adderall XR 20mg or Adderall 10mg BID, not Adderall XR 10mg.
- See adhdmedicationguide.com for a frequently updated guide to ADHD medications.
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