Compatibility of piperacillin sodium plus tazobactam with selected drugs during simulated Y-site injection

The compatibility of piperacillin sodium plus tazobactam with selected drugs during simulated Y-site administration was studied. A 5-mL sample of piperacillin sodium 40 mg/mL plus tazobactam 5 mg/mL (Zosyn) in 5% dextrose injection was combined with a 5-mL sample of each of 75 other drugs at concentrations used clinically. Each combination was prepared in duplicate in glass culture tubes, with the order of mixing being reversed between the duplicates; storage was in constant fluorescent light at 22 degrees C. The admixtures were examined visually in normal fluorescent light and in high-intensity light zero, one, and four hours after preparation. A turbidimeter was used to measure the turbidity of each drug combination at the same intervals. Samples showing visual or turbidimetric evidence of incompatibility were subjected to particle sizing and counting. The majority of the drugs tested were compatible with Zosyn injection; most combinations had a turbidity of less than 0.1 nephelometric turbidity unit. However, 24 drugs exhibited various incompatibilities, including increased turbidity, particulate formation and precipitation, and color change. Piperacillin sodium 40 mg/mL plus tazobactam in 5% dextrose injection was visually compatible with the majority of the drugs tested for up to four hours at 22 degrees C but incompatible with 24 drugs.