In the modern era of the aging society, the number of bedridden elderly patients is increasing gradually, and many of them are troubled by pressure ulcers (decubitus ulcers), which are often serious, resulting in refractory skin ulcers. 1,2) Various dosage forms have been developed to treat skin ulcers such as pressure ulcers. [3][4][5][6] We also prepared a patch with a tamarind gum-sucrose hydrogel containing silver sulfadiazine, and demonstrated that the formulation displayed a better effect than Geben ® cream. 7,8) Generally, a pressure ulcer goes through the stages of an period of infection and necrosis, an agglutination period, and a proliferation period of granulation and epidermis in that order until cure. To each stage, many formulations, including ointments, creams, films and dressings, have been developed. [9][10][11][12][13][14] Ointments containing minocycline, which exhibited controlled release, were reported recently because minocycline is highly effective against pressure ulcer bacteria.15) Many formulations applied to pressure ulcers possess an antibacterial function 6,7,11,12,14,15) or potential to enhance the proliferation of granulation or epidermis. 4,[16][17][18] Namely, substances with such abilities and high safety can be candidates as agents for the treatment of pressure ulcers.We focused on the liquid obtained by hydrothermal extraction of Sasa veitchii (CARR.), named Kumazasa extract (KE), because the extract has been reported to exhibit various biological functions such as antibacterial action, anti-ulcer property, cell repair function and anti-tumor action. [19][20][21][22][23] It was reported that the active ingredients associated with antiinflammatory, anti-ulcer and anti-tumor functions might be polysaccharides, which are the major components of KE. 23,24) In this study, a deep skin ulcer model was induced by skin removal and subsequent frostbite as a pressure ulcer-like model in rats, 8) and used in the in vivo studies. For the formulations, chitosan (CS) was adopted as the polymer support for solid components in KE, named EXT, because CS has been found useful to protect other types of wound, 25,26) probably due to its antibacterial, immune-enhancing function etc.27-31) Naturally dried and freeze-dried chitosan films containing KE were developed as different types of dosage forms. The film types of formulations are considered to be excellent for usability. In the present studies, KE alone, the films and other clinically used formulations were examined for in vivo efficacy using the deep skin ulcer model, and histological analyses were performed for some formulations. MATERIALS AND METHODS MaterialsLiquid obtained by hydrothermal extraction of Sasa veitchii (CARR.), named Kumazasa extract (KE), which was composed of water (50%, w/w) and residual components, named EXT (50%, w/w), was supplied by Hoshi Pharmaceutical Co., Ltd. (Japan). Chitosan 1000 (deacetylation degree of 80%; viscosity grade 1200 cP at 0.5% at 20°C) was purchased from Wako Pure Chemicals Industries, Ltd., and use...