Stability of admixtures of pethidine and metoclopramide in aqueous solution, 5% dextrose and 0.9% sodium chloride

Abstract

Objective: To study the stability of admixtures of pethidine and metoclopramide in aqueous solution, 0.9% sodium chloride and 5% dextrose preparations. Method: Aqueous mixtures of 1 ml of 50 mg/ml pethidine with 2 ml of 5 mg/ml metoclopramide were prepared in plastic syringes, while the 0.9% sodium chloride and 5% dextrose admixtures, each containing 7.35 mg/ml of pethidine and 0.15 mg/ml of metoclopramide, were prepared in infusion bags. The preparations were stored under light and dark conditions at 32°C for 48 h. Samples were collected at 0, 0.5, 1, 2, 4, 6, 8, 24, 32 and 48 h. A high-performance liquid chromatographic method was developed to separate and quantify both drugs. Results: All preparations were found to be physically and chemically stable for at least 48 h, as concentration changes were within 10% of their initial level, with no development of haze, precipitate or colour. Light appeared to have a negligible effect. Although pH changes were observed, they were inconsistent and were within the ranges in which the drugs are expected to remain stable. Pethidine and metoclopramide admixtures can, therefore, on stability grounds be used for the concomitant management of pain, nausea and vomiting.