Frozen fortified antibiotic in ophthalmic solutions stability during 2 months

Purpose: Fortified antibiotic ophthalmic solutions are regularly administered as an immediate treatment for bacterial keratitis. The fortified antibiotics were used to be self-prepared by nurses. To solve this problem, pharmacy staff studied the stability of three 5% solutions of vancomycin, amikacin and ceftazidim, prepared in aseptic conditions from parenteral antibiotic solutions. Methods: Solutions were frozen at -20°C. Portions of each solution were examined before storage and over a 75-days period. Ceftazidim and amikacin were dilute in 0,9% sodium chloride and vancomycin in 5% dextrose. Over a 75 days period, physical, pharmacological (absorbance spectra) properties and sterility of each stock solution were studied. Results: The pH of amikacin (6,51), ceftazidim (6,47) and vancomycin (3,77) remained stable during the 75 days period. Osmolarities also remained stable (367, 488 and 351 mOsm/L). There were no significant differences in the concentration, osmolarity and pH of the three antibiotic solutions before storage and after 75 days of freezing. Over a 75 days period, stability of amikacin, ceftazidim and vancomycin remained constant; no contamination was detected before storage and after 75 days. Conclusions: Topical fortified antibiotic solutions can be stored 75 days at -20°C (15 days quarantine). After, these eye-drops should be stored at 4°C and should be discarded after 3 days.