Fat-globule size in a propofol emulsion containing sodium metabisulfite

Abstract

Purpose. The size distribution of fat globules from previously unopened, unexpired vials of Gensia Sicor's 1% propofol injectable lipid emulsion was studied. Methods. Fat globules in 20-mL samples from 50- and 100-mL vials of Gensia Sicor's 1% propofol emulsion containing 0.025% sodium metabisulfite were measured and counted by a laser-based, single-particle optical sensing technique. Measurements were performed during May 2001, June 2002, and October 2002, corresponding, respectively, to 17-21, 5-9, and 1-5 months before the vials' expiration dates, depending on the lot. Between measurements, the vials were stored at 4-22°C. It was assumed that the pH for all lots was 4.5-6.4. Two separate lots of the innovator propofol emulsion (AstraZeneca) containing EDTA and having a labeled pH of 7.0-8.5 were analyzed in October 2002 in a post hoc assessment as the vials neared their expiration date. Results. In May 2001, the volume-weighted percentage of fat globules with a diameter of >5 μm (PFAT5) was <0.05% for all seven Gensia Sicor lots. In four of the lots, PFAT5 increased significantly between May 2001 and June 2002. In all seven lots, PFAT5 increased significantly between May 2001 and October 2002. The two lots of the AstraZeneca product, tested two or three months before expiration, had low PFAT5 values. Conclusion. In samples from unopened, unexpired, and properly stored vials of Gensia Sicor propofol formulated at pH 4.5-6.4, PFAT5 increased over 18 months and in most cases exceeded 0.05% by the end of the study.