This study investigated whether gemcitabine, adsorbed onto activated carbon particles (GEM-AC), increased the concentration of gemcitabine at the injection site and in the regional lymph nodes in an experimental animal model and a clinical study. The adsorption isotherm for GEM-AC was defined, and the concentration and distribution of gemcitabine in rats (n = 50) and in patients with pancreatic cancer (n = 8) was investigated. Drug concentrations in plasma, tumour samples, lymph nodes and at the injection site were measured after GEM-AC or gemcitabine solution (GEM-Sol) were subcutaneously injected into the left hind foot pad in rats, or into pancreatic tumours in patients. These experiments showed that GEM-AC was selectively delivered to the regional lymph nodes and the injection site, from which it slowly released greater amounts of gemcitabine to maintain the free concentration of gemcitabine at a relatively high level for a long period of time. The administration of GEM-AC might enhance the anticancer effects of gemcitabine.