Consider the challenge to the preservative system.How great a challenge will there be?Should this test be designed (as suggested by CVMP and ISO guidance) to simulate normal use, and then challenged using current compendial preservative testing? If that is to be the case, then a significant logistical issue arises: as the product is intentionally packaged in a volume sufficient for only 28 days of use (generally 5 mL/unit) at the end of the 28 days there is very little left to test. This makes performing the test extremely challenging as the preservative test normally requires approximately 100 mL of sample.