Chemical stability and in vitro antimicrobial efficacy of diluted silver sulfadiazine powder and cream over a six‐month period

• Published in: Veterinary dermatology 2024-12, Vol.35 (6), p.704-715
• Main Authors: Lopresto, Christopher M., Palmeiro, Brian S., Cole, Stephen D., Xu, Xin, Dietrich, Jaclyn, Stefanovski, Darko
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - chemistry; Anti-Bacterial Agents - pharmacology; Anti-Infective Agents, Local - administration & dosage; Anti-Infective Agents, Local - chemistry; Anti-Infective Agents, Local - pharmacology; Antimicrobial activity; Antimicrobial agents; Colonies; dogs; Drug Stability; Drug Storage; E coli; Escherichia coli; Liquid chromatography; Mass spectroscopy; Methicillin; Microbial Sensitivity Tests; Otitis; Otitis externa; Powder; Powders - pharmacology; Proteus mirabilis; Pseudomonas; Pseudomonas aeruginosa; Shelf life; silver sulfadiazine; Silver Sulfadiazine - administration & dosage; Silver Sulfadiazine - pharmacology; Skin Cream - pharmacology; Staphylococcus; Staphylococcus pseudintermedius; Sulfadiazine; Sulfamethoxazole; Tandem Mass Spectrometry; Trimethoprim
• ISSN: 0959-4493; 1365-3164; 1365-3164
• DOI: 10.1111/vde.13289

Background Silver sulfadiazine (SSD) is commonly formulated into otic preparations to treat otitis externa, although evidence of stability and antimicrobial efficacy with long‐term storage is lacking. Objectives To evaluate the effect of storage time on chemical stability and in vitro antimicrobial activity of SSD diluted in sterile water, including two 1% suspensions using SSD pharmaceutical‐grade powder stored at room temperature (RT) in plastic or sterile glass bottles, and a 1:9 dilution using prescription SSD 1% cream stored at RT in a sterile glass bottle. Materials and Methods Liquid chromatography–tandem mass spectrometry (LC–MS/MS) assessed chemical stability. Trimethoprim/sulfamethoxazole‐susceptible and trimethoprim/sulfamethoxazole‐resistant strains of Staphylococcus pseudintermedius (SP), meticillin‐resistant (MR) SP, S. schleiferi (SS), MRSS, Pseudomonas aeruginosa, Proteus mirabilis and Escherichia coli evaluated by 24 h time–kill analysis assessed in vitro antimicrobial efficacy. Each assessment was performed at zero, one, three and six months of storage. Results LC–MS/MS showed no significant change in concentration over time for any suspension. When adjusted for time and species/strain, all SSD suspensions showed significant reductions in colony forming units (cfu)/mL at 24 h (p