FDA finalizes recommendations for studying absorption of active ingredients in topically-applied OTC monograph drugs

Topical over-the-counter drug products applied to the skin, such as topical antiseptic or sunscreen, are often meant to be used repeatedly over time. People may wonder if these product are absorbed, and if so, what happens: for example, how much gets into the body or bloodstream, whether they’re safe to use, and whether there are any considerations for using these products in children or older individuals. 

While research indicates that some topical drugs can be absorbed into the body through the skin, this does not mean these drugs are unsafe, but this finding does call for further testing to determine the safety of repeated use and that once in the body the ingredient or product does not cause harm. The FDA has been working to better understand the level of this absorption and the resulting safety profiles for topical drugs,” said Janet Woodcock, M.D., director of the FDA’s Center for Drug Evaluation and Research. “Over the past several decades, collecting human absorption data to study potential risks of using a product according to the maximum levels of its directions for use has become a routine part of the application for new drugs before approval, and is also an important type of study for topical drug products marketed under the OTC drug monograph system. 

Today, in response to requests from industry for direction on the best way to collect these data for active ingredients seeking inclusion in an OTC monograph, we are issuing final guidance that provides recommendations on how to design and conduct these studies, known as Maximal Usage Trials, or MUsT trials. This information will help identify the need for further testing to assess potential safety concerns and help determine whether an adequate safety margin exists for an active ingredient to be included in a relevant OTC monograph.

For more information, please visit: FDA In Brief.