As a novel administration method of ivermectin (IVM) for scabies treatment, we proposed a "whole-body bathing method (WBBM)". In this method, the patients would bathe themselves in a bathing fluid containing IVM at an effective concentration. Previously, we demonstrated that WBBM could deliver IVM to the skin but not to the plasma in rats. In the present study, to assess the clinical validity of the method an arm bathing examination (first trial) and a whole-body bathing examination (second trial) were conducted in healthy volunteers. In both the first and second trials, after bathing in fluid containing IVM, the exposure in the stratum corneum was higher compared with that after taking IVM p.o. as reported previously. IVM was not detected in plasma at any sampling point after the whole-body bathing in the second trial. Furthermore no serious adverse events were found. These results in both trials suggest that WBBM can deliver IVM to the human stratum corneum without systemic exposure or serious adverse effects in healthy volunteers, and at concentrations that would be adequate for scabies treatment.

Scabies is an intensely pruritic ectoparasitic skin infestation caused by the mite Sarcoptes scabiei and affects over 130 million people and hampers quality of life. 1 Topical permethrin, which is included in the World Health Organization's list of essential medicine, is the standard treatment for scabies. 2 In recent years, permethrin and ivermectin (IVM) have become the most relevant treatment options for scabies. 3 Using external treatments is very laborious and must be applied completely to the whole body; scabies may recur if some areas are unpainted. 4 Conversely, although an oral preparation of IVM is convenient for treatment, it can cause some systemic adverse drug reactions such as liver dysfunction. 5 To address the problems mentioned above, as a novel external application, we devised a whole-body bathing for exposure to IVM (IVM-WBB) in which patients would simply be bathed in a fluid containing IVM. Previously, we demonstrated that IVM is delivered into the skin but not into the blood via IVM-WBB in rats 6 and healthy volunteers. 7 In healthy volunteers, no adverse drug reactions were observed and the maximum IVM concentration in the stratum corneum after IVM-WBB was much higher than that after oral IVM administration. 8 In this clinical trial, we aimed to examine the efficacy and safety of IVM-WBB in elderly patients with scabies. | ME THODS | Trial design and schedule of IVM-WBBA multi-institutional trial for elderly patients with scabies was conducted in cooperation with five hospitals and three nursing care facilities. The ethics committee of Tokyo University of Science (no. 12002) and each participating facility approved the trial. All trial procedures were conducted according to the Declaration of Helsinki. Figure 1 illustrates the schedule of IVM-WBB treatment and sample collection.