Stability of Butorphanol–Tropisetron Mixtures in 0.9% Sodium Chloride Injection for Patient-Controlled Analgesia Use

Tropisetron is an adjuvant for butorphanol used in intravenous patient-controlled analgesia (PCA) and has been reported to provide superior pain control. It is efficacious in reducing the incidence of postoperative nausea and vomiting. However, this admixture is not available commercially and stability data applicable to hospital practice are limited. This study aimed to describe the drug compounding and evaluates the long-term (up to 14 days) stability of butorphanol and tropisetron in 0.9% sodium chloride injection for PCA use. In this study, commercial solutions of butorphanol tartrate and tropisetron hydrochloride were combined and further diluted with 0.9% sodium chloride injection to final concentrations of butorphanol tartrate 0.08 mg/mL and tropisetron hydrochloride 0.05 mg/mL. The polyolefin bags and glass bottles were stored at 4°C and 25°C for up to 14 days. The drug stabilities were determined by visual inspection, pH measurement, and high-pressure liquid chromatography assay of drug concentrations. The data obtained for admixtures prepared and stored at temperatures of 25°C and 4°C show the drugs have maintained at least 98% of the initial concentration. All solutions remained clear and colorless over the 14-day period, and the pH value did not change significantly. The results indicate that admixtures of butorphanol tartrate 0.08 mg/mL and tropisetron hydrochloride 0.05 mg/mL in 0.9% sodium chloride injection solution were stable for 14 days when stored in polyolefin bags or glass bottles at 4°C and 25°C and protected from light. The infusion is feasible for manufacturing in pharmacy aseptic units and can be stored for up to 14 days for routine use in PCA infusions.