A prospective study in healthy volunteers of the topical absorption of a 5% rifaximin cream.

Rifaximin, the active ingredient of an antibiotic cream, is a synthetic antibiotic derived from rifamycin and characterized by minimal absorption. In animals, no absorption was detected after topical application on the skin. The question as to whether there is detectable absorption in man by the same administration route is answered by this study in healthy volunteers. One gram of the cream containing 5% rifaximin was massaged on a sizable surface of skin prepared prior to application by mechanical abrasion. Rifaximin concentrations in blood and urine were then determined by means of HPLC-electrochemical-coulometrical detection. Concentrations in all samples being less than 2.5 ng/ml, the method's limit of detection, it is concluded that there is no detectable absorption in man. No adverse reactions were reported during this one day study. The results confirm studies performed in animals which showed that rifaximin is not absorbed and is well tolerated.