For the 4.4 million American children who have attention deficit hyperactivity disorder (ADHD), there will soon be another option for treatment. The Food & Drug Administration recently approved the first prodrug to treat the condition: lisdexamfetamine dimesylate (Vyvanse).
"The drug is designed to have a reduced abuse potential," said Marcia L. Buck, Pharm.D., FCCP, clinical pharmacy specialist at University of Virginia's Children's Hospital and associate professor of pediatrics in the schools of medicine and nursing. Since it requires oral ingestion to be converted to the active drug, the capsule contents are unlikely to be sought out for inhalation or injection, she explained. "Lisdexamfetamine is converted to dextroamphetamine and L-lysine in the GI tract. Although the exact mechanism is not well understood, the conversion is believed to be the result of first-pass metabolism in the gut lining and/or the liver."
"While it appears that this drug will be very similar to products already on the market, at this time there are no published studies comparing lisdexamfetamine to either dextroamphetamine or methylphenidate," explained Buck. But, she added, there may be situations in which it would be advantageous for a patient to have a medication supply that is not easily tampered with or has very little street value. In fact, in clinical studies, lisdexamfetamine produced a lower preference on the scale of "Drug Liking Effects" [DLE] among known substance abusers.
Lisdexamfetamine will be classified as a Schedule II controlled substance and is expected to launch during the second quarter of 2007. According to Buck, the recommended starting dose is 30 mg taken orally once daily in the morning. The dose may then be increased by up to 20 mg per day at weekly intervals, up to a maximum daily dose of 70 mg. "The capsules are available in 30-, 50-, and 70-mg strengths," she said.
Because Shire's leading ADHD product, Adderall XR, will lose its patent protection in two years, the company is hoping to transition patients currently taking Adderall XR over to lisdexamfetamine, which will maintain its patent until 2024.
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