Evaluation of spontaneous contamination of ocular medications

Background: In order to evaluate whether single-dose ophthalmic preparation s in 0.5-ml containers can safely be used within 24 h after the first openi ng, eigth different sterile ocular medications containing timolol, jaluroni c acid, diclofenac, ketotifen, pilocarpine, formocortal, formocortal-gentam ycin, and tetryzoline-feniramine (Farmigea, Italy) were opened and tested f or spontaneous bacterial contamination after exposure to air. Methods: Samp les (10 yl) were collected from exposed ophthalmic preparations after 0, 2, 4, 8 and 24 h. Results: No viable microorganisms were detected during and at the end of the evaluation period. In order to assess whether the residen t or pathogenic ocular bacterial population due to repeated handling might contaminate the medications, about 10(5) cells of different species (Staphy lococcus aureus, coagulase-negative staphylococci, Streptococcus pneumoniae , Streptococcus spp., Corynebacterium spp., Pseudomonas aeruginosa, Neisser ia spp., Acinetobacter spp., Haemophilus influenzae, Escherichia coliand Ca ndida albicans) were added to the containers and incubated at 37 degreesC o r at room temperature. Samples were collected and the number of viable bact eria was estimated. The antibacterial effect of the ophthalmic compounds va ried depending on the species considered. Tetryzoline-feniramine, pilocarpi ne, ketotifen and formocortal-gentamycin exhibited a frank bactericidal act ivity (< 100 survivors after 18-24 h of exposure) against the great majorit y of the species tested. Conclusion: These results indicate that the risk o f spontaneous contamination of ophthalmic preparations after their first op ening is low, and that all preparations tested exhibit an aspecific antibac terial activity. As a consequence, the safe usage of these ocular medicatio ns could be extended from the recommended 3 h to at least 24 h after the fi rst usage. Copyright (C) 2001 S.Karger AG, Basel.