Stability of carbenicillin and oxacillin frozen in syringes.

The stability of carbenicillin disodium and oxacillin sodium following storage in syringes for three months at -20 C was studied. Employing a spectrophotometric assay, it was found that carbenicillin (2500 mg/ml) and oxacillin (200 mg/ml) remained stable in both glass and plastic syringes for three months when frozen at -20 C. Stability was not altered by storage in either glass or plastic, nor by the size of the syringe used. Although the results were favorable, additional evidence is necessary before the practice of freezing reconstituted carbenicillin and oxacillin in syringes is advocated.