title: Stability of intravenous admixtures of aztreonam and ampicillin.
abstract: The stability of aztreonam and ampicillin in intravenous admixtures containing both drugs was studied. Each of the following drugs and combinations of drugs was added to both 5% dextrose injection and 0.9% sodium chloride injection: aztreonam 10 and 20 mg/mL, ampicillin sodium 5 and 20 mg/mL, aztreonam 20 mg/mL and ampicillin sodium 20 mg/mL, aztreonam 20 mg/mL and ampicillin sodium 5 mg/mL, aztreonam 10 mg/mL and ampicillin sodium 20 mg/mL, and aztreonam 10 mg/mL and ampicillin sodium 5 mg/mL. One of each of these admixtures was stored at 25 degrees C for 48 hours and 4 degrees C for seven days. At various storage times the admixtures were inspected for visual changes and 2-mL samples were examined microscopically for crystalline and particulate matter, tested for pH, and assayed by high-performance liquid chromatography. No visual changes were observed. In the two-drug solutions, pH was influenced by concentrations of the two drugs and stability of the drugs was influenced by the solution pH. The pH of single-drug aztreonam admixtures did not change during storage, but the pH of single-drug and two-drug admixtures containing ampicillin decreased. In single-drug admixtures, aztreonam loss under both storage conditions was less than 10% but ampicillin loss was more than 10% in 0.9% sodium chloride injection and more than 50% in 5% dextrose injection. The stability of ampicillin was increased in the presence of aztreonam, and the stability of aztreonam was decreased in the presence of ampicillin.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000667:Ampicillin / Q000032:analysis*; D000900:Anti-Bacterial Agents / Q000032:analysis*; D001398:Aztreonam; D002626:Chemistry, Pharmaceutical; D004355:Drug Stability; D004356:Drug Storage; D006863:Hydrogen-Ion Concentration; D007275:Injections, Intravenous; D009391:Nephelometry and Turbidimetry
chemical_list: D000900:Anti-Bacterial Agents; D000667:Ampicillin; D001398:Aztreonam