COMPARISON OF THIMEROSAL EFFECTIVENESS IN THE FORMULATION OF EYE DROPS CONTAINING NEOMYCIN SULFATE AND CHLORAMPHENICOL

Objective: This study was aimed to compare the preservative efficacy of thimerosal in eye drops formulation containing neomycin sulfate and chloramphenicol as the active agents.Methods: Determination of thimerosal concentration in combinations with chloramphenicol and neomycin sulfate was carried out using the agar diffusion method. Then the thimerosal ineffective and minimal concentration was formulated into eye drops, each with 0.5% neomycin sulfate and 0.5% chloramphenicol as the active ingredient. Evaluation of eye drops was carried out for 28 d, which included: visual observation, pH measurement, sterility, and effectiveness test.Results: Thimerosal at a minimum concentration of 0.001% remain to provide antibacterial activity against common eyes contaminants. Both eyes drops containing neomycin sulfate, and chloramphenicol resulted in clear solution, sterile, and stable in the pH and antibacterial potency,showed the efficacy of thimerosal’s role in eye drops at the lowest concentration. But, the thimerosal stability as a preservative agent was affected by the pH values of the eye drops solution. Therefore, the effectivity of thimerosal in chloramphenicol (pH 7.19-7.22) was better than neomycin sulfate (6.45-6.60). Compared with F0 (without thimerosal), the increasing of inhibitory diameter in F1 and F2 from both eyes drops formula exhibited the significant role of thimerosal as the preservative agent. The synergistic effect of the preservative agent in the formula produced a better product stability than the eye drop without thimerosal. Conclusion: Thimerosal at a minimum concentration of 0.001% exhibited effective concentration as a preservative in eye drops containing 0.5% neomycin sulfate and 0.5% chloramphenicol.