Effect of freezing and microwave thawing on the stability of six antibiotic admixtures in plastic bags

Am J Hosp Pharm. 1982 Jan;39(1):104-8.


The stability of six antibiotics in intravenous fluids in polyvinyl chloride containers after freezing and microwave-thawing is reported. Tobramycin sulfate 160 mg, amikacin sulfate 1 g, ticarcillin disodium 3 g, clindamycin phosphate 300 mg, nafcillin sodium 1 g, and ampicillin sodium was also diluted in plastic bags of 0.9% sodium chloride injection 50 ml. For each antibiotic except ampicillin sodium, three bags were prepared and assayed immediately for antibiotic content. Two of the bags were frozen at -20 degrees C for 30 days and then thawed, one by exposure to room-temperature air and the other by microwave radiation. Each was assayed immediately and after 8 and 24 hours storage at room temperature. The third bag was not frozen, but was stored at room temperature and assayed at 8 and 24 hours. Five bags of ampicillin sodium were prepared-three in 0.9% sodium chloride, which were frozen at -20, -30, and -70 degrees C, and two in 5% dextrose, which were frozen at -30 and -70 degrees C. All ampicillin solutions were stored 30 days, assayed, microwave-thawed, and assayed again. All antibiotics except ampicillin retained 90% or more potency when microwave-thawed after storage at -20 degrees C for 30 days, and after subsequent storage at room temperature for 24 hours. Ampicillin sodium was stable in 0.9% sodium chloride when stored at -30 or -70 degrees C, microwave-thawed, and stored up to eight hours at room temperature. Ampicillin sodium was stable in 5% dextrose when stored at -70 degrees C and microwaved-thawed, but its potency declined to 70.5% after eight hours storage at room temperature.

MeSH terms

  • Anti-Bacterial Agents*
  • Bacillus subtilis / drug effects
  • Biological Assay
  • Drug Combinations
  • Drug Packaging
  • Drug Stability
  • Freezing*
  • Infusions, Parenteral
  • Microwaves*
  • Plastics


  • Anti-Bacterial Agents
  • Drug Combinations
  • Plastics