The Food and Drug Administration (FDA) has expressed concerns about the therapeutic equivalence in two generics of methylphenidate HCl extended-release (Concerta), which is commonly prescribed to treat attention-deficit-hyperactivity disorder (ADHD)

The two generics are manufactured by Mallinckrodt and Kudco Ireland. After analyzing adverse event reports, an internal FDA re-examination of previously submitted data, and FDA laboratory tests of Mallinckrodt and Kudco Ireland products, the agency reported that the generic products may not produce the same therapeutic benefits for some patients as the branded version of methylphenidate HCl ER.

Methylphenidate HCl ER is designed to release the drug over a 10–12 hour period. However, the Mallinckrodt and Kudco products were shown to release the drug at a slower rate during the 7–12 hour range. A reduced release rate may lead to patients not achieving the desired therapeutic effect.

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As a result, the FDA has changed the therapeutic equivalence rating from AB to BX for the Mallinckrodt and Kudco products. The BX rating means that while products are still approved and can be prescribed, they are no longer recommended as automatic substitutes at the pharmacy for the branded version. Also, the FDA has modified its draft guidance for industry for bioequivalence testing for methylphenidate HCl ER tablets.

Mallinckrodt and Kudco have been requested to confirm the bioequivalence of their products within six months, or voluntarily pull their products off the market.

Janssen Pharmaceuticals, which manufactures the branded methylphenidate HCl ER, also has an agreement with generic manufacturer Actavis to market an authorized generic version. However, analysis of that product found it to be bioequivalent to the branded version.

This article originally appeared on MPR