Aim: To evaluate the antiemetic efficacy and safety of olanzapine in Japanese women with nausea and/or vomiting refractory to the standard antiemetic regimen. 

Methods: We retrospectively reviewed the medical records of consecutive female patients with early breast cancer who underwent highly emetogenic chemotherapy at our hospital from January 2009 to March 2013. Patients with grade 2 or 3 nausea and/or vomiting despite receiving standard antiemetics (5-hydroxytryptamine3 receptor antagonists and dexamethasone 20 mg on day 1, and 4 mg dexamethasone on days 2 and 3) in the first chemotherapy cycle received an additional 2.5–10 mg olanzapine from days 1 to 3 in the subsequent cycles. We assessed patient characteristics, olanzapine dose, nausea and vomiting grades before and after adding olanzapine, and adverse effects. 

Results: We reviewed 20 patients with poor control in the first chemotherapy cycle, despite receiving standard antiemetics, who received olanzapine from the second cycle. Nausea and vomiting improved in 75% and 70% of cases, respectively, despite poor control during the first cycle, while an additional 10% of cases achieved a complete response (no emesis, no rescue) in the second cycle. No grade 3/4 adverse events were noted, but 50% and 30% of subjects complained of grade 1/2 drowsiness and dizziness, respectively, prompting a reduction in the olanzapine dose. Efficacy was retained at the lower dose. 

Conclusion: Olanzapine has excellent antiemetic efficacy in Japanese women with chemotherapy-induced nausea and vomiting refractory to standard antiemetics. The 
recommended dose of olanzapine for Japanese women appears to be lower than for Caucasians.