ABSTRACT
Objective: In this study, pharmaceutical properties were compared between the original and generic ophthalmic solutions containing betamethasone.Methods: The squeeze force, drop weight, surface tension, pH, kinematic viscosity, and total number of drops were measured. The drop volume was calculated from the drop weight and specific gravity. Information on preservatives contained in each product was collected from package inserts.Results: There was a significant difference in the squeeze force between the original and generic drugs. The pH and kinematic viscosity did not differ between the drugs. The drop volume was in the range of 30.3 to 47.2 μL, and the surface tension ranged between 33.7 and 65.2 mN/N. The total number of drops was approximately 100 in the original drug, being the lowest.Conclusion: The results of this study showed that the squeeze forces of all generic products but RINBETA PF, which was contained in a specific container, were smaller than that of the original product. The drop volumes of 2 generic products were ≥ 15-μL smaller than that of the original product, but they were within the permissible range. The maximum difference in the surface tension was approximately 33 mN/N, suggesting that drug solution relatively frequently overflows from the eyes. The total number of drops for all generic products was greater than that for the original product, suggesting that the former can be used at a higher frequency. Based on these results, pharmacists must select products in accordance with individual patients.