Stability of vancomycin in an extemporaneously compounded ophthalmic solution.

The stability of vancomycin 31 mg/mL (as the hydrochloride) in an artificial tears solution at -10, 4, 25, and 40 degrees C was studied. Vancomycin power was reconstituted with sterile water for injection to a concentration of 50 mg/mL. Artificial tears solution containing 0.3% hydroxypropyl methylcellulose, 0.1% dextran 70, 0.01% benzalkonium chloride, and 0.05% edetate disodium was used to produce a final concentration of 31 mg/mL. Triplicate solutions for each storage temperature and sampling time were prepared. The solutions were stored at -10, 4, 25, and 40 degrees C. Samples were taken initially and at 3, 7, 10, 21, 30, 45, and 60 days for visual inspection and analysis by high-performance liquid chromatography. All solutions remained clear and colorless at -10, 4, and 25 degrees C throughout the study period. By day 3, crystalline particles formed in the solutions stored at 40 degrees C. No substantial change in pH was observed at any time. At -10 degrees C, the solutions retained more than 90% of their initial vancomycin concentrations throughout the study period. The solutions retained a mean of at least 90% of the initial drug concentration for 21 days at 4 degrees C and for 7 days at 25 degrees C. For the solutions stored at 25 or 40 degrees C, less than 85% of the initial vancomycin concentration remained after 10 and 3 days, respectively. Vancomycin 31 mg/mL (as the hydrochloride) in an artificial tears solution was stable for 45 days at -10 degrees C, 10 days at 4 degrees C, and 7 days at 25 degrees C in the tears solution's original container.