Incidence of nausea and vomiting induced by oxycodone administered with prochlorperazine in Japanese cancer patients.

BACKGROUND Nausea and vomiting are the most frequent side effects of opioids and may cause the opioids to be discontinued. New methods for preventing opioid-induced nausea can improve cancer pain management. Oxycodone is one of the most frequently used opioid used in Japan because patients receiving oxycodone report less nausea and vomiting than do patients receiving morphine. The reported incidence of oxycodone-induced nausea varies widely, although the true incidence remains unclear. As a first step toward preventing oxycodone-induced nausea, we aimed to determine the incidence of and risk factors for oxycodone-induced nausea and vomiting. METHODS In this observational study, we analyzed a series of consecutive inpatients with cancer who received oxycodone with prochlorperazine as a preventive antiemetic agent. Oxycodone (5 mg) was administered either at 08:00 and 20:00 or at 09:00 and 21:00, and prochlorperazine (5 mg) was also given at the same times for 5 days. RESULTS Of the 145 enrolled patients, 138 were suitable for analysis. The incidence of nausea was 18.1%, and that of vomiting was 5.8%. The incidence of nausea was higher, but not to a significant degree, in women than in men (P=0.07). Furthermore, the incidence of vomiting in women was equal to that in men (P=0.28), whereas the incidences of both nausea (P=0.99) and vomiting (P=0.89) in elderly patients were equal to those in younger patients. In addition, the incidence of nausea (P=0.52) and vomiting (P=0.91) in patients with digestive system cancer was equal to that of patients with non-digestive system cancer. CONCLUSIONS The incidence of nausea induced by oxycodone with prochlorperazine was 18.1% in opioid-naïve Japanese inpatients. Female sex may be a risk factor for oxycodone-induced nausea. These results suggest that a clinical study would require 314 participants (157 in each group) to decrease the incidence from 18% to 8% (10% decrease) with a new preventive treatment (alpha error=0.05, beta error=0.2).