Chemical Stability of Ceftazidime Compounded in Saline, Glycerin and Dexamethasone-SP Solutions Stored at -20°C, 4°C and 25°C Over a 60 Day Period.

Background: Chronic cases of canine otitis externa (OE) often develop infections with Pseudomonas aeruginosa (PA). Given the organism's high level of resistance, veterinary surgeons often turn to compounded solutions. Limited data describing the stability and potency of compounded ceftazidime (CAZ) solutions are available, which may affect clinical outcome.

Hypothesis/objectives: To evaluate the chemical stability of compounded glycerin (GLY) and dexamethasone sodium phosphate (DEX-SP) CAZ solutions in three different storage temperatures over a 60-day period. Based on previous evaluations, CAZ concentrations would decrease with increased temperature and time.

Materials and methods: Ceftazidime was compounded at 10 mg/mL with 100 mL 0.9% sodium chloride (NA + CAZ), 100 mL glycerin +0.9% sodium chloride (GLY + CAZ) and 100 mL dexamethasone sodium phosphate +0.9% sodium chloride (DEX-SP + CAZ), stored at -20°C, 4°C and 25°C for 60 days. Mass spectrometry was used to analyse CAZ stability at specific time points (Day[D]0, D7, D14, D28, D60).

Results: Chemical stability of CAZ concentrations was affected by storage time, temperature and diluent. CAZ concentrations decreased over time with increased temperature; frozen CAZ concentrations remained stable over time for all solutions.

Conclusions and clinical relevance: Compounded CAZ stability varies by diluent, storage temperature and storage duration. NA + CAZ and DEX-SP + CAZ solutions are stable for ≤ 28 days refrigerated and retain potency for ≥ 60 days if stored frozen. These solutions offer alternative options for treatment of PA OE.