INTRODUCTION Dapsone induces methemoglobinemia by oxidant stress; ethyl pyruvate (EP) is an antioxidant and radical oxygen species scavenger. This study was conducted to evaluate the effect of EP on methemoglobinemia induced by dapsone. METHODS Male Sprague-Dawley rats were divided into an EP group and a control group. Rats in the EP group were administered dapsone (40 mg/kg) via the stomach and then EP (40 mg/kg) was injected intraperitoneally. Rats in the control group were administered dapsone followed by Ringer's lactate solution. Methemoglobin concentrations were measured at 90, 180, and 360 min after dapsone administration. RESULTS Methemoglobin concentrations were not different between time points in the control group. However, in the EP group, the methemoglobin concentrations were significantly lower than those of the control group at 90 and 180 min, but this difference was no longer apparent at 360 min. CONCLUSION A single intraperitoneal dose of EP was able to reduce methemoglobinemia induced by dapsone for a short period of time, but this effect was not sustained.