USA – FDA Finalizes Maximal Usage Trials Guidance for Topical OTC Drugs

The US Food and Drug Administration (FDA) on Thursday finalized guidance on conducting maximal usage trials (MUsT) to support the inclusion of an active ingredient in an over-the-counter (OTC) monograph.

MUsTs are conducted to determine the in vivo bioavailability of topical drugs and can help FDA understand the potential for systemic exposure to a topically applied active ingredient.

The guidance finalizes a draft version released for comment in May 2018 and comes just days after an FDA studypublished in JAMA found that all four sunscreen active ingredients tested were systemically absorbed under maximal usage conditions, demonstrating the need for more testing of topically applied OTC drug products.

According to FDA, the MUsT guidance was developed in response to comments it received from industry on its draft and final guidances on demonstrating safety and effectiveness for nonprescription sunscreens that called on the agency to provide more detailed guidance on MUsTs…