2025 Volume 27 Issue 2 Pages 31-42
Objective: This study aimed to elucidate how the physical properties of containers and formulations of glaucoma eyedrops contribute to differences in squeezing force and drop volume among products within the same pharmacological class. This study seeks to generate valuable insights for product selection, patient guidance, and formulation improvement.
Design: Physical measurements of multiple glaucoma eyedrop products were made under various conditions, followed by comparative analyses of the data and the characteristics of each product's container and solution. The study determined how the product selection and instillation technique affected the squeezing force and drop volume.
Methods: Eyedrop products commonly used as first-line treatments were evaluated, including all brand-name drugs and high-usage generic drugs. Based on the clinical guidelines and NDB open data, 17 products were selected, consisting of prostanoid receptor-related drugs and beta blockers. Each product was tested at various angles to measure squeezing force and drop volume. These measurements were combined with basic container characteristics, including the material, design, and size, to compare and identify trends. Multivariate regression analysis was conducted to examine the factors affecting squeezing force.
Results: The squeezing force varied significantly among the products (0. 68-1. 57 times the average), whereas the drop volume exhibited relatively minor differences (0.79-1.12 times the average). Some products showed marked variability in squeezing force and drop volume between drops, depending on residual volume and container angle. Additionally, containers with smaller finger-contact areas, made of materials other than polyethylene, non-cylindrical designs, and formulations with higher viscosity were estimated to require greater squeezing force.
Conclusion: Squeezing force and drop volume vary significantly by product and instillation technique, which highlights the importance of understanding these differences when prescribing and guiding patients. Further systematic studies on other eyedrop products should be carried out to enhance appropriate drug use and inform the development of user-friendly formulations.
