Stability‐indicating HPLC assays for the determination of piritramide and droperidol in PCA solution

Summary What is known and Objective:  A mixture of morphine and droperidol is a well-established antiemetic for reducing the risk of postoperative nausea and vomiting. A mixture of piritramide and droperidol has not yet been evaluated in this context. Our objectives were to develop a high-performance liquid chromatographic assay for piritramide and droperidol in 0·9% saline, and to establish their stability under defined storage conditions. Methods:  The separation and assay of both drugs were attempted by high performance liquid chromatography (HPLC) using a RP-select B column and a mobile phase of 57:43% v/v methanol-monosodium phosphate solution 0·05 M at a flow rate of 1·2 mL/min. UV detection at 205 and 246 nm for piritramide and droperidol were used, respectively. Results and Discussion:  The HPLC method was successful. Linearity was shown for piritramide from 0·075 to 0·013 mg/mL and for droperidol from 0·8 to 0·2 mg/mL. The intra- and inter-day relative standard deviation (RSD, %) was 0·27% and 0·54% for piritramide and droperidol, respectively. The two drugs were stable for at least 72 h when stored under ambient light at room temperature. What is new and Conclusion:  Seventy-five milligrams piritramide and 2·5 mg droperidol diluted to 50 ml with 0·9% saline should be suitable for clinical use. At this dilution, a Dipidolor® and Xomolix®, mixture, was stable when stored under ambient light exposure at room temperature for at least 72 h.