An alternate approach for preservative testing of ophthalmic multiple-dose products.

The USP XIX Preservative Effectiveness Test when used alone to evaluate the preservative efficacy of ophthalmic multiple-dose products, does not provide sufficient information to detect a marginally preserved product. A modified testing procedure that incorporates kill rate determination and increased recoveries into the existing USP XIX method is proposed. This new procedure allows for a more quantitative evaluation of preservative effectiveness of formulations microbiologically challenged one or more times in the presence or absence of an organic load. The information provided by this test method will be helpful not only in formulating new products but also in evaluating new preservative test requirements.