By: Theresa M. Michele, M.D.
All drugs have some risk — even over-the-counter (OTC) drugs available without a prescription — and the FDA is always taking steps to help ensure their safety. When you take a pill, you generally expect that some of the active ingredient gets into your body, but what about when you apply a topical product to the skin? How much of the product gets absorbed through the skin and enters the bloodstream, and is it safe? At the FDA, we’ve been working to better understand the absorption and safety profile of topical OTC products such as sunscreens and topical antiseptics. We are particularly interested in learning how these products affect vulnerable populations such as children, the elderly, and pregnant and breastfeeding women.
Until recently, there was little data available to demonstrate the extent to which topical OTC drugs are absorbed into the bloodstream after application, and whether there are any long-term consequences of this. In fact, many topical OTC products were first marketed when these products were thought not to be absorbed through the skin and when there were no effective methods available to measure absorption. Now, better measurement tools are available, and research indicates that topical drugs can indeed be absorbed into the body through the skin.
Consequently, the FDA has been generally encouraging manufacturers to collect data on the potential risks of a topical drug when used according to the maximum limits of the product’s instructions, what we call Maximal Usage Trials or MUsT studies. Most recently we included MUsT studies among the list of safety and efficacy studies recommended for sunscreen active ingredients being evaluated under a new marketing pathway established by the Sunscreen Innovation Act in a final guidance for industry in November 2016. Now we are issuing draft guidance that, when finalized, will provide recommendations to industry on how to design and conduct MUsT studies for topical active ingredients that are under consideration for inclusion in an OTC monograph.
The draft guidance includes discussions about how to study the topical active ingredient’s effects on specific subgroups of vulnerable patients like children and the elderly. The studies require a relatively small sample of patients for a short period of time and should not be overly burdensome. In fact, this draft guidance reflects the same safety and efficacy standards that have applied to all drug products marketed under the OTC Monograph System for more than 40 years.
Absorption studies have contributed significantly to the FDA’s knowledge of the safety of topical prescription products. Applying a similar level of safety research to active ingredients being considered for inclusion in an OTC monograph to that which currently exists for prescription products can help the FDA determine whether these ingredients should be included in OTC products marketed without approved applications.
Theresa M. Michele, M.D., is the Director of the Division of Nonprescription Drug Products, Office of New Drugs, at the FDA’s Center for Drug Evaluation and Research