Influence of container structures and content solutions on dispensing time of ophthalmic solutions

PURPOSE: To investigate the influence of container structures and content solutions on the time of dispensing from eye dropper bottles. METHODS: Eye dropper bottle models, solution models (filtrate water/surfactant solution) and a dispensing time measuring apparatus were prepared to measure the dispensing time. RESULTS: With filtrate water and pressure thrust load of 0.3 MPa, the dispensing time significantly increased from 1.1 ± 0.5 seconds to 4.6 ± 1.1 seconds depending on the decrease of inner aperture diameters from 0.4 mm to 0.2 mm (P < 0.0001). When using the bottle models with inner aperture diameters of 0.4 mm or larger, the dispensing time became constant. The dispensing time using surfactant solution showed the same tendency as above. When pressure thrust load was large (0.07 MPa), the solution flew out continuously with inner aperture diameters of 0.4 mm or larger and the dispensing time could not be measured. The inner aperture diameter most strongly explained the variation of the dispensing time in both the content solutions in the multiple linear regression analysis (filtrate water: 46%, R(2) = 0.462, surfactant solution: 56%, R(2) = 0.563). CONCLUSIONS: Among content solutions and container structures, the dispensing time was mostly influenced by the diameter of the inner aperture of bottles.