The Anatomy of a Formula—Antiperspirant Sticks, Soft Solids and Gels

By: Eric S. Abrutyn, TPC2 Advisors Ltd., Inc.

Posted: May 4, 2009, from the May 2009 issue of Cosmetics & Toiletries.

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Additives
The fourth category of AP ingredients is comprised of miscellaneous additives. Miscellaneous additives represent a catch basin for functionally optional ingredients. Examples include: talc, corn starch, silica, fragrances, antioxidants, chelating agents, colorants, botanicals (that are usually tied to a specific claim) and odor-controlling agents.

Commercial Products
The last several years have seen relatively few changes in AP solid formulations. The changes that have occurred mainly center around exchanging the AP actives and the percentages used, along with the addition of other ingredients to allow for extended claims beyond wetness control. Some recent claims and associated technologies are shown in Table 2.

In addition, Formulas 1–7 give examples of approximate compositions of commercial AP/deodorant solid formulas and the procedures used to make them. These formulas were taken from sources of public domain and are estimates of the ingredient percentages and procedures used, to provide readers with a starting point for their own formulation work. It is suggested that readers perform a patent search to ensure they are not infringing on any existing and protected technologies.

Tackling Development Issues
Some unusual barriers exist in the formulation of APs. First, since AP solids are considered drugs in the United States and are fully or partially regulated globally, there are rigid requirements relating to the selection of actives, percentage of actives allowed, and testing, manufacturing and labeling. As an example, aluminum-only actives can be used at up to 25% concentration and aluminum-zirconium actives can be used at up to 20% concentration, based on an anhydrous basis.

Additional regulations include required testing for the percentage of wetness protection in commercial antiperspirant products via prescribed FDA protocols and statistical analyses. In addition, commercial antiperspirants must be manufactured in an FDA registered facility and operated under prescribed Good Manufacturing Procedures, and the FDA final monograph for antiperspirants strictly regulates advertising and labeling claims and communication to the consumer.