Comparison of Ramosetron With Ondansetron for Prevention of Intrathecal Morphine-Induced Nausea and Vomiting After Primary Total Knee Arthroplasty: A Randomized Control Trial

Spinal anesthesia with intrathecal morphine is a reliable, easy to apply, and cost effective method for controlling pain after total knee arthroplasty (TKA). However, postoperative nausea and vomiting (PONV) is a major concern. 5-Hydroxytryptamine receptor 3 (5-HT₃) antagonists like ondansetron and ramosetron are commonly used for preventing PONV, but the optimal choice remains unclear. We conducted a study to assess the effectiveness of ramosetron and ondansetron, hypothesizing that the longer acting ramosetron may be better than ondansetron in the first 48 hours after TKA, performed with spinal anesthesia and intrathecal morphine.

Patients were randomized preoperatively to either intravenous ondansetron (8 mg) or ramosetron (0.3 mg). The primary outcomes were the incidence rates of PONV. Secondary outcomes were the need for a rescue antiemetic (metoclopramide), pain score, patient satisfaction, and adverse drug reactions (ADRs) at 0-6, 6-12, 12-24, and 24-48 hours.

Ninety patients were evaluable; 45 patients/arm. Compared with ondansetron, ramosetron was associated with significantly lower incidence rates of nausea at: (1) 12-18 hours: 3/45 vs 11/45 (P = .016), (2) 18-24 hours: 1/45 vs 9/45 (P = .005), and vomiting at 18-24 hours: 1/45 vs 6/45 (P = .044). There were no significant differences in the use of rescue-antiemetic medicine, pain score, patient satisfaction, and ADRs.

Preoperative ramosetron provided more prolonged PONV prophylaxis than ondansetron after TKA in our setting, and had a similar ADR profile. Other trials are needed to confirm our results before ramosetron is adopted widely.