Can I take Vyvanse (lisdexamfetamine) if I have run out of my Adderall (amphetamine/dextroamphetamine)?

Do Not Substitute Vyvanse for Adderall Without Physician Authorization

You should not take Vyvanse as a substitute for your Adderall without explicit direction from your prescribing physician, even though both are stimulant medications used to treat ADHD. While these medications are pharmacologically related and both are first-line treatments for ADHD, they are distinct controlled substances with different dosing equivalencies, pharmacokinetic profiles, and regulatory requirements 1.

Why This Matters

Different Medications Require Different Prescriptions

• Vyvanse (lisdexamfetamine) and Adderall (amphetamine/dextroamphetamine) are separate controlled substances that require individual prescriptions
• Taking a medication not prescribed to you is both illegal and medically inappropriate, regardless of similarity in therapeutic class
• Your physician needs to authorize any medication changes to ensure proper dosing and monitoring

Pharmacological Differences

While both medications work through similar mechanisms (blocking reuptake and increasing release of dopamine and norepinephrine), they have important distinctions 1, 2:

Vyvanse is a prodrug:

• Lisdexamfetamine must be converted to dextroamphetamine in the blood by red blood cells before becoming active 2
• This conversion creates a delayed onset of approximately 1 hour compared to immediate-release amphetamines 3
• Peak effects occur around 3.5-4.4 hours after administration 2

Adderall contains mixed amphetamine salts:

• Immediate-release formulations act more rapidly
• Extended-release versions have different pharmacokinetic profiles than Vyvanse
• The ratio of dextroamphetamine to levoamphetamine differs from Vyvanse (which produces only dextroamphetamine)

Dosing Is Not Interchangeable

The doses are not equivalent on a milligram-per-milligram basis. For example, 30 mg of lisdexamfetamine is equivalent to approximately 8.9 mg of dextroamphetamine base 2. Taking an arbitrary dose of Vyvanse could result in:

• Underdosing: Leading to inadequate symptom control and functional impairment
• Overdosing: Risking cardiovascular effects (tachycardia, hypertension), agitation, insomnia, or more serious complications 2

What You Should Do Instead

Immediate Actions

1. Contact your prescribing physician immediately to report that you've run out of medication
2. Request an emergency prescription refill or authorization for early refill if appropriate
3. Do not take someone else's medication, including Vyvanse, even if offered by family or friends

If You Cannot Reach Your Physician

• Contact your pharmacy to see if they can provide an emergency supply (regulations vary by location)
• Seek care at an urgent care clinic or emergency department if you're experiencing significant functional impairment
• Be prepared to explain your medication history and current prescription

Clinical Context from Guidelines

Current ADHD treatment guidelines emphasize that medication adjustments and changes are common and expected in ADHD management 4, 1. The evidence shows that:

• More than 90% of patients respond to one of the stimulant medications when both methylphenidate and amphetamine classes are tried 4
• Switching between stimulant medications should be done systematically under physician supervision with appropriate dose titration 1
• If methylphenidate provides inadequate benefit, lisdexamfetamine is recommended as the next option, but this requires proper medical evaluation 1

Important Safety Considerations

Both medications carry risks that require monitoring:

• Cardiovascular effects (blood pressure, heart rate)
• Growth parameters in children
• Potential for misuse and diversion 5
• Drug interactions and contraindications

Your physician needs to evaluate these factors before authorizing any medication change, even between similar stimulants 1.

Bottom Line

Call your doctor today to address your medication shortage through proper medical channels. The similarity between these medications does not make self-substitution safe or appropriate. Proper ADHD management requires ongoing physician oversight, including medication selection, dosing, and monitoring 4, 1.