Typically how long does it take for 20 mg of vyvanse (lisdexamfetamine) to start working?

No studies exist on : onset & duration of action of Vyvanse (lisdexamfetamine) in teens. In children 6-12, the average time for onset is 1.5 hours & duration is 13 hours. Vyvanse (lisdexamfetamine) is inactive till the d-amphetamine is cleaved from what becomes lysine. Times vary depending on how fast a patient metabolizes the drug. Your dose will be titrated weekly by 10-20 mg. for optimal effect, unless side effects occur.Check BP & heart rate often.