A US shortage of the new generic version of Vyvanse, an ADHD medication, is due in part to federal limits on production, according to an industry group representing generic drug makers.

Manufacturers haven’t been able to secure enough raw material “to launch their products at full commercial scale,” according to a letter from the Association for Accessible Medicines addressed to the Drug Enforcement Administration, which sets the limits on production that the industry must follow. These restrictions on obtaining the drug’s active ingredients have curbed generic manufacturing, and people and insurers are paying more for the branded drug as a …