Risk of microbial contamination of unit-dose eyedrops within twenty four hours after first opening.

The purpose of this study was to evaluate the risk of microbial contamination of sterile, preservative-free, unit-dose ocular medications within 24 h after the first opening. Four different unit-dose ocular medications (cromolyn sodium, timolol, gentamicin sulfate, and betamethasone) in 1 mL containers, were tested. After opening, the preparations were stored in an acrylic protector with or without cap, at room temperature or in a refrigerator at 4 degrees C. Samples were collected for microbiological cultures at 0, 4, 10, 14, and 24 h after opening from the identical container. No bacteria or fungus was detected in the samples throughout the period of the study. Microbial air contamination of the experimental environment was also studied. The culture results of environmental microbial air contamination were positive for both bacteria and fungi. This study suggests that unit-dose eyedrops remain free of microbial air contamination for up to 24 h after the first opening.