PT - JOURNAL ARTICLE AU - Qasem M. Abu Shaqra AU - Rania M Al-Groom AU - Aseel Q Abu Shaqra TI - Antimicrobial Effectiveness in Eye Drops: Limited sterility Versus Reduction in Microbial Count. AID - 10.5731/pdajpst.2019.009845 DP - 2020 Jan 01 TA - PDA Journal of Pharmaceutical Science and Technology PG - pdajpst.2019.009845 4099 - http://journal.pda.org/content/early/2020/01/15/pdajpst.2019.009845.short 4100 - http://journal.pda.org/content/early/2020/01/15/pdajpst.2019.009845.full AB - Eye drops are sterile preparations intended for instillation into the eye. All major pharmacopoeias require these products to pass the antimicrobial effectiveness test (AET). This test is similar to that used for oral dosage form despite the fact that both product categories differ in their microbiological specifications. The eye drops might pass the official requirements of the AET but in practice, contaminants introduced into the preparation might not be killed prior to its next use by the patient and this may compromise ocular health. The objective of this work was to investigate the possible application of a limited sterility testing in a multi-challenge test that mimics more closely actual life use of eye drops. The AET was performed on 12 brands of eye drops and results were compared with the suggested pass criteria of various pharmacopoeias. The multi-challenge test was designed and used to demonstrate the ability of each tested product to kill the entire challenge organism population within a few hours. The results demonstrated that all products investigated were in compliance with the AET acceptance requirements of the United States Pharmacopoeia <51> and the "B" criteria of the European Pharmacopoeia <5.1.3>. Only 2 of the tested products did not comply with the no recovery term of Ph Eur <5.1.3> 'A' criteria. Products repeatedly challenged with Pseudomonas aeruginosa ATCC 9027 (103 CFU ml-1) were found to be self-sterilizing within 2 h of each inoculation. In conclusion, all tested products passed the acceptance criteria of the USP <51>, class B of the Ph Eur <5.1.3> and the multi-challenge test. The size of the challenge organism population in the AET seems to be severe for eye drops and the pass criteria of the BP Appendix XVI is the most stringent. The no recovery term given in the Ph Eur <5.1.3> should be defined to a specified range.