Chemical compatibility of cefmetazole sodium with ranitidine hydrochloride during simulated Y-site administration

The stability of cefmetazole sodium and ranitidine hydrochloride was studied under conditions simulating administration via a Y-injection site into a primary infusion line. Cefmetazole sodium was reconstituted with both 0.9% sodium chloride injection (50 mL or 100 mL) and 5% dextrose injection (50 mL) to produce premixing concentrations of cefmetazole 10 and 20 mg/mL. Ranitidine hydrochloride injection was diluted with 50 mL 0.9% sodium chloride injection to give premixing concentrations of ranitidine 1 mg/mL. To simulate Y-site administration, 2 mL of cefmetazole was mixed with 2 mL of ranitidine in a 10-mL glass test tube. All study mixtures were prepared in triplicate and stored at room temperature (22-23 degrees C) under normal fluorescent room lighting. Samples of these admixtures were inspected for visual changes and tested for pH. The concentrations of two drugs were immediately determined by stability-indicating high-performance liquid chromatographic assay methods after mixing and at 1, 2, and 4 hours. No visual changes were observed. The pH in the admixtures was influenced by concentrations of the two drugs. The pH of each single-drug solution did not change during the study period. On the other hand, the pH of any admixtures of cefmetazole and ranitidine solutions prepared with 0.9% sodium chloride or 5% dextrose injection, decreased. Cefmetazole in any of the admixtures with ranitidine retained greater than 95% of its original concentration for 4 hours.(ABSTRACT TRUNCATED AT 250 WORDS)