At Oita University Hospital, we switched our usage of pemetrexed(PEM)from brand-name to generic drugs. We conducted a comparative study of the preparation efficiency and therapeutic safety with the brand-name product and examined the economic effect thereof. The incidence of adverse drug reactions was investigated retrospectively using electronic medical records for patients who received PEM brand-name and generic drugs at our hospital between April 2021 and December 2022. The preparation time per mg was significantly shorter in the generic group at 0.17(0.08-0.38)seconds compared to 0.34(0.15-0.94)seconds for the brand-name group(p<0.01). Regarding the safety comparison, none of the 13 eligible patients developed new hematologic or non-hematologic toxicities of Grade 2 or higher after switching to the generic product. The switch to generics had an economic impact of 7,369,278 yen during the study period. The results suggest that switching from brand-name to generic products is reasonable from the perspectives of therapeutic safety and economic benefits, as well as the expected improvement in preparation efficiency.