The Stability of Antibacterials in Polyethylene Glycol Mixtures

Abstract

The antibacterial activity of penicillin and bacitracin is rapidly destroyed in polyethylene glycol bases. Aminoacridine, neomycin, oxytetracycline and streptomycin are affected less. Attempts to improve the stability of incorporated penicillin by modifications to the base, such as reformulation, adjustment of pH to neutrality and heat treatment, were unsuccessful. Commercially available polyethylene glycols, particularly the lower molecular weight polymers, showed oxidising activity thought to be due to peroxides. Catalase and horse blood destroyed the oxidising activity of polyethylene glycol bases and prevented the destruction of added penicillin during a test period of 10 days. The addition of reducing agents, although apparently removing the oxidising activity when tested chemically, did not improve the stability of penicillin mixed with the treated bases. Since catalase did not completely protect aminoacridine, neomycin and oxytetracycline from inactivation by polyethylene glycol bases, it was concluded that other inactivating factors were operative