On February 23, the FDA approved Shire and New River’s Vyvanse (lisdexam- fetamine dimesylate) for the treatment of ADHD in children. Vyvanse is the molecule dextroamphetamine (trade names Dexedrine and Dextrostat) attached to the amino acid lysine. After this inactive “pro-drug” is absorbed through the GI tract into the bloodstream, the liver hydrolyzes the molecule, cleaving off the lysine and producing the active drug d-amphetamine. This delivery system slows the release of d-amphetamine, so that the concentration peaks at 3.5 hours instead of 3 hours, which is when plain d-amphetamine reaches its maximum concentration (see Dexedrine prescribing information, accessed at http://www.fda.gov/cder/foi/label/2006/ 017078s040lbl.pdf). While classified as a Schedule II controlled substance as exist- ing stimulants, Vyvanse produces no high if snorted, and a 100 mg dose made drug abusers less buzzed than a 40 mg dose of Dexedrine. However, at 150 mg of Vyvanse there were no differences between the two on the “drug likeability scale.” (See the manufacturer’s Web site at www.vyvanse.com.)
TCPR’s Take: Vyvanse is not in pharmacies yet, so it is too early to judge whether there are any clinical advantages. If it is truly less abusable, this would be its primary advantage. The cynic in TCPR notes that Vyvanse is timed to be marketed shortly before Adderall XR goes off patent. Since Shire makes both drugs, watch for shenanigans such as “shortages” of Adderall XR just as Vyvanse hits the shelves.
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