Background
Patients undergoing laparoscopic gynecological surgery are at high risk of postoperative nausea and vomiting (PONV). The aim of this study was to determine the effective dose of ramosetron, a 5-hydroxytryptamine type 3 receptor antagonist, for prophylaxis of PONV in this patient population.
Methods
In this prospective, randomized, double-blinded study, 180 patients received a single administration of either IV ramosetron 0.3 mg (R0.3 group), 0.45 mg (R0.45 group), or 0.6 mg (R0.6 group) immediately after the end of surgery. In all groups, ondansetron 8 mg was added to an intravenous patient-controlled analgesia (IV-PCA) fentanyl solution. The primary outcome was the incidence of PONV during the first 48 h after surgery. The severity of nausea, pain score, and adverse events were assessed. 
Results
The incidences of PONV were not different among three groups (35%, 38%, vs. 35%, P = 0.905). The severities of nausea, pain scores, and additional analgesic requirements were similar among the groups. The incidence of adverse events including dizziness, headache, and sedation were not different among the groups. However, more patients in R0.3 group required early IV-PCA discontinuation compared to those in R0.45 and R0.5 groups, primarily because of PONV and/or dizziness (24% vs. 9% and 5%, P = 0.038). 
Conclusions
Increased dose of ramosetron was not found to reduce the incidence of PONV in high risk patients undergoing laparoscopic gynecological surgery.

Dose-ranging study of ramosetron for the prevention of nausea and vomiting after gynecologic laparoscopic surgery: a prospective randomized study