Evaluation of preservative effectiveness in ophthalmic drops by microbial challenge test

Abstract

Ophthalmic drops face the problem of microbial spoilage during their use and storage which affects consumer safety. Protection of these multiple dosage products against microbial contamination is usually achieved by addition of a suitable preservative, but sometimes some clinical hazards are observed even after addition of preservatives. The aim of present study was to evaluate and compare the effectiveness of different preservatives present in three ophthalmic drop samples collected from local market through microbial challenge test. The samples of ophthalmic drops were challenged with 3 bacterial and 2 fungal strains and results were periodically (0, 7, 14 and 28 days) investigated. The number of survive microorganisms were determined using standard microbiological dilution pour-plate method. More than 1 log reduction of microbial counts was observed in all samples at 7 day. Moreover, the log reductions in microbial count were significantly increased up to 28 day. Results showed that ophthalmic drop samples having different preservatives i.e. Benzalkonium chloride, Benzyl alcohal and Phenyl mercuric nitrate were effective against all the challenged microorganisms.  However, Phenyl mercuric nitrate was found to be most effective. Hence, from this study it is concluded that preservatives present in all tested ophthalmic drop samples are effective in preventing contamination of the product during their use and storage.