In this report, we highly recommend the coadministration of first-generation serotonin receptor antagonists, dexamethasone, and aprepitant for chemotherapy-associated nausea and vomiting in patients with breast cancer receiving doxorubicin and cyclophosphamide (AC) chemotherapy. Aprepitant has an advantage of high efficacy rates for the treatment of nausea and vomiting; its disadvantages include the high cost and interactions with other drugs. Herein, we report the information provided by pharmacists regarding the effective timing of the coadministration of first-generation serotonin receptor antagonists and dexamethasone for nausea and vomiting in patients receiving AC chemotherapy for breast cancer. The primary end point was the proportion of patients who achieved a complete response (CR; no emesis or use of rescue therapy)in cycle 1 after receiving AC chemotherapy. A total of 46 patients were enrolled in this study between November 2010 and December 2011. The overall rate of CR (0-120 hours) was 85%. The rates of acute (0-24 hours) and delayed (24-120 hours)CR were 85% and 93%, respectively. These findings suggest that the information provided by pharmacists regarding the effective timing of the coadministration of first-generation serotonin receptor antagonists and dexamethasone is effective in patients who cannot be administered with aprepitant.