PURPOSE: We aimed to study the stability and the in vitro antibacterial potency of ceftazidime and vancomycin eyedrops against Pseudomonas aeruginosa and Staphylococcus aureus, respectively, under different storage temperatures and light conditions. METHODS: Solutions of ceftazidime 50 mg/ml and vancomycin 50 mg/ml were prepared by reconstituting with balanced salt solution (BSS) and stored at 4 degrees C and at 24 degrees C with and without exposure to light. The minimum bactericidal concentrations against P. aeruginosa and S. aureus were measured to evaluate the antimicrobial potency over a 4-week period. Changes in the pH values and physical characteristics of the solutions were recorded over the same period of time. RESULTS: The antibacterial potency of ceftazidime decreased significantly from days 3 and 7 onwards at storage temperatures of 24 degrees C and 4 degrees C, respectively, but was not affected by light exposure. The pH value progressed from acidic to alkaline, peaking at day 3, in all solutions. The antibacterial potency of vancomycin remained stable during the 4-week period, but its pH showed a slight progression from acidic to less acidic, in all solutions. CONCLUSIONS: Ceftazidime eyedrops in BSS appear to remain effective against P. aeruginosa for > or = 7 days when stored at 4 degrees C, but were less effective when stored at 24 degrees C. Loss of antibacterial potency coincides with the appearance of visual and olfactory signs of degradation. The transient rise in pH at day 3 is a matter of possible concern, however, as it may affect patient tolerance. By contrast, vancomycin eyedrops in BSS can be safely used for > or = 4 weeks, stored at either 4 degrees C or 24 degrees C.
PURPOSE: We aimed to study the stability and the in vitro antibacterial potency of ceftazidime and vancomycin eyedrops against Pseudomonas aeruginosa and Staphylococcus aureus, respectively, under different storage temperatures and light conditions. METHODS: Solutions of ceftazidime 50 mg/ml and vancomycin 50 mg/ml were prepared by reconstituting with balanced salt solution (BSS) and stored at 4 degrees C and at 24 degrees C with and without exposure to light. The minimum bactericidal concentrations against P. aeruginosa and S. aureus were measured to evaluate the antimicrobial potency over a 4-week period. Changes in the pH values and physical characteristics of the solutions were recorded over the same period of time. RESULTS: The antibacterial potency of ceftazidime decreased significantly from days 3 and 7 onwards at storage temperatures of 24 degrees C and 4 degrees C, respectively, but was not affected by light exposure. The pH value progressed from acidic to alkaline, peaking at day 3, in all solutions. The antibacterial potency of vancomycin remained stable during the 4-week period, but its pH showed a slight progression from acidic to less acidic, in all solutions. CONCLUSIONS:Ceftazidime eyedrops in BSS appear to remain effective against P. aeruginosa for > or = 7 days when stored at 4 degrees C, but were less effective when stored at 24 degrees C. Loss of antibacterial potency coincides with the appearance of visual and olfactory signs of degradation. The transient rise in pH at day 3 is a matter of possible concern, however, as it may affect patient tolerance. By contrast, vancomycin eyedrops in BSS can be safely used for > or = 4 weeks, stored at either 4 degrees C or 24 degrees C.