Lisdexamfetamine (L-lysine-d-amphetamine) is an inactive molecule prodrug (Vyvanse®) consisting of the psychostimulant d-amphetamine coupled with the essential amino acid L-lysine. Lisdexamfetamine was developed so that the psychostimulant is released and activated more slowly as the prodrug molecule is hydrolyzed—consequently cleaving off the amino acid-during the first pass through the intestines and/or the liver. Essentially, this makes lisdexamfetamine an extended-release formulation of d-amphetamine; however, the release characteristics are integral to the molecule itself, rather than simply the pill construction.

Vyvanse was developed by New River Pharmaceuticals, who were bought by Shire Pharmaceuticals shortly before lisdexamfetamine began being marketed. Vyvanse is FDA approved for the treatment of attention-deficit hyperactivity disorder in pediatric patients ages 6–12, and in adults. Vyvanse pills are available in dosages of up to 70 mg.

Unlike Adderall, which contains roughly 75% d-amphetamine and 25% l-amphetamine, lisdexamfetamine is a single-enantiomer amphetamine formula. Certain individuals exhibit a better clinical response to the mixed isomer preparation, thus they may continue to use Adderall XR or equivalent generics. A 25 mg Vyvanse capsule would be molecularly equivalent to a 10 mg Dexedrine Spansule (both the aforementioned pharmaceuticals are about 7.425 mg dextroamphetamine), although a 25 mg Vyvanse capsule is not commercially available (see dosage strengths below).

However, this molecular equivalence ratio does not imply that these respective doses of Vyvanse and Dexedrine XR (Spansule) are bioequivalent--the two formulations have slightly different pharmacokinetic profiles. That is, while the AUC for the aforementioned pharmaceuticals is equivalent, the peak exposure (Cmax) to the active compound dextroamphetamine is about 50% higher for Vyvanse than for Dexedrine XR.

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