The fixed combination of fortified vancomycin and amikacin ophthalmic solution--VA solution: in vitro study of the potency and stability.
OBJECTIVE
We compared the in vitro potency and stability of a fixed combination of vancomycin and amikacin solution (VA solution) with amikacin or vancomycin solution.


METHODS
Solutions of 2% amikacin (20 mg/mL) and of 5% vancomycin (50 mg/mL) and VA solution (each 1 mL contained 20 mg of amikacin and 50 mg of vancomycin) were prepared from parenteral antibiotics by reconstituting them with sterile injection water and refrigerated (4 degrees C) in the dark. Triplicate 5-mL portions of each solution were tested before storage and 7 and 14 days after preparation for potency of antimicrobial activity by the disk diffusion method and for stability.


RESULTS
There were no significant differences in the diameter of zones of inhibition of VA solution compared with amikacin or vancomycin solution within a 2-week period. Visual inspection revealed that all solutions remained clear, colorless, and particle-free at 4 degrees C throughout the study period. For osmolarity, the VA solution was much higher than that of either amikacin or vancomycin solution at all tested times and more near the well-tolerated range of human eyes. There were no significant differences at days 0, 7, or 14 for either vancomycin, amikacin, or VA solution. For pH, the VA solution was higher than that of vancomycin solution (nearly equal to that of amikacin solution) at each time and more near the level of normal tear film. The pH did not differ significantly for either vancomycin, amikacin, or VA solution at all tested times.


CONCLUSIONS
The vancomycin and amikacin ophthalmic solutions can be mixed together with the same potency and stable physical properties. It may be useful in the treatment of bacterial keratitis pending clinical trials to determine its effectiveness and safety.
Lin
Jane-Ming
JM
Department of Ophthalmology, China Medical University Hospital, Taichung, Taiwan.
Tsai
Yi-Yu
YY
Fu
Ya-Lin
YL
D000583:Amikacin / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004338:Drug Combinations; D004355:Drug Stability; D006863:Hydrogen-Ion Concentration; D008826:Microbial Sensitivity Tests; D009883:Ophthalmic Solutions / Q000494:pharmacology; D009994:Osmolar Concentration; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000254:growth & development; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000254:growth & development; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000254:growth & development; D014640:Vancomycin / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D009883:Ophthalmic Solutions; D014640:Vancomycin; D000583:Amikacin