The stability and compatibility of methylprednisolone sodium succinate in admixtures with cimetidine hydrochloride in 5% dextrose injection were determined. Admixtures containing methylprednisolone sodium succinate, in concentrations equivalent to methylprednisolone 0.4 or 1.25 mg/mL, and cimetidine 3 mg/mL (as the hydrochloride salt) were prepared in 5% dextrose injection 100 mL. Control solutions containing each drug alone at the same concentrations were also prepared. The admixtures were prepared in triplicate and were kept in polyvinyl chloride infusion containers at controlled room temperature (24 degrees C). Immediately after mixing and at 2, 4, 8, 12, and 24 hours, samples were removed and visually inspected, measured for pH, and assayed by stability-indicating high-performance liquid chromatography to determine the concentrations of methylprednisolone 21-succinate ester and cimetidine. No visual evidence of incompatibility was noted either with the unaided eye or a microscope. No substantial changes in pH occurred over the study period. The addition of cimetidine decreased the pH of the methylprednisolone sodium succinate control solutions from about 7.3 to about 5.6. The concentrations of methylprednisolone 21-succinate ester and cimetidine in both test and control solutions did not change significantly over the 24-hour study period. Methylprednisolone sodium succinate, in concentrations equivalent to methylprednisolone 0.4 and 1.25 mg/mL, was chemically stable and visually compatible in admixtures with cimetidine 3 mg/mL (as the hydrochloride salt) in 5% dextrose injection 100 mL at 24 degrees C for 24 hours.