Clinical Pharmacology Corner: Maximal Usage Trials Draft Guidance

FDA Announces Availability of a Draft Guidance, “Maximal Usage Trials for Topical Active Ingredients Being Considered for Inclusion in an Over-the-Counter Monograph: Study Elements and Considerations”

On May 23, 2018, the U.S. Food and Drug Administration (FDA) announced the availability of a draft guidance for industry entitled "Maximal Usage Trials for Topical Active Ingredients Being Considered for Inclusion in an Over-the-Counter Monograph: Study Elements and Considerations." 

A Maximal Usage Trial (MUsT) is a standard approach to assessing the in vivo bioavailability of topical drug products. The draft guidance provides recommendations for the design and conduct of MUsT for topical active ingredients that are under consideration for inclusion in an over-the-counter (OTC) drug monograph. It outlines the critical study elements, data analysis, and considerations for special topic areas (e.g., pediatrics, geriatrics).

A critical safety consideration for topical drugs is whether applying the drug to the skin results in dermal penetration and systemic exposure to the active ingredient, and, if so, to what extent. The underlying goal of the MUsT is to evaluate systemic exposure levels under conditions relevant to real-world use that maximize the potential for dermal absorption. This information helps identify potential safety concerns and helps determine whether an adequate safety margin exists for an active ingredient to be included in a relevant OTC monograph or if additional safety data are needed. The FDA recognizes that more than one study design can provide the desired information and that many factors can influence the specific approach to be used. Study sponsors are encouraged to seek FDA’s feedback on their overall approach and the design of a MUsT. 

The “Maximal Usage Trials for Topical Active Ingredients Being Considered for Inclusion in an Over-the-Counter Monograph: Study Elements and Considerations” draft guidance is available athttps://go.usa.gov/xQmpv. Please refer to the draft guidance for more details. 

FDA is publishing the draft guidance to collect additional public comments. You may submit your comments to this draft guidance by July 23, 2018 to the Docket No. FDA–2018–D–1456 available athttps://www.regulations.gov. Your comments do make a difference and can impact the outcomes of FDA regulatory policy. Share your knowledge and experience, and make your voice count.