What has a greater impact on an alcohol-based hand rub's antimicrobial efficacy: the content level of alcohol (70% vs. 90% by volume) or form of product delivery (gel vs. foam)?
Actually, neither format nor alcohol content is as important as the product's formulation, according to an award-winning poster presentation at the 2011 APIC Conference in Baltimore last month.
In a study funded and conducted by GOJO Industries, maker of Purell hand sanitizer products, researchers set out to challenge previous studies suggesting that gel and foam hand rubs are less effective than rinses, and that hand rubs should have at least 75% to 80% ethanol concentrations to meet global efficacy requirements. The Food and Drug Administration requires a minimum 2 log10 reduction from baseline after 1 application and 3 log10 reduction from baseline after 10 applications.
The researchers, led by Sarah Edmonds, MS, a clinical scientist with GOJO, applied 5 different alcohol-based hand rubs to 12 subjects:
Product A: 70% ethanol by volume, gel product.
Product B: 70% ethanol by volume, foam product.
Product C: 90% ethanol by volume, gel product.
World Health Organization-recommended formulation for an 80% ethanol rinse product.
WHO-recommended formulation for a 75% isopropanol rinse product.
After 1 application, with a log10 reduction of 3.58, Product A was statistically superior to Product C (3.12 log10 reduction) and the WHO-recommended formulations (3.07 and 3.12, respectively), while Product B's log10 reduction of 3.55 was statistically superior to the WHO-recommended ethanol formulation. After 10 applications, both Products A and B were statistically superior to the other 3 products by a fairly wide margin (log10 reductions of 3.50 and 4.00 vs. 1.80, 2.39 and 2.04, respectively).
The takeaways? Alcohol concentrations above 70% aren't necessary to guarantee a high level of efficacy, and gels and foams are fully capable of meeting FDA efficacy requirements for alcohol-based hand rubs, say the researchers.
They conclude that it's the formulation of the product -- its "recipe," so to speak -- not its alcohol content or delivery format, that matters when it comes to efficacy. "It is our experience that it is very important to formulate a product with the right set of excipients (inactive ingredients) to maximize the activity of the formulation," explains Ms. Edmonds. "We have found that some ingredients will enhance the activity of the active ingredient, alcohol, whereas other ingredients can cause the efficacy to decline." She recommends that users ask hand rub manufacturers for data showing their product works, not just that it has the recommended active ingredients.
The researchers also note that the test products' change in efficacy between 1 and 10 applications highlights "the importance of evaluating products after multiple uses."
Irene Tsikitas
