ABSTRACT
The objective of a challenge test is to determine the susceptibility of a product to microbial contamination. The United States Pharmacopoeia and British Pharmacopoeia tests are not intended to mimic the conditions which may lead to contamination during manufacture and use and may not predict performance of preservative systems in practice. The death rate of organisms has been shown to be affected by the growth medium and inoculum preparation procedure. The test length should be long enough to allow slow-growing organisms to emerge and on this basis a test period of 28 days may be too short. The chapter presents an approach to preservative testing of pharmaceuticals which describes the development of a laboratory test and comparison of test results with manufacturing experience of a product. It describes a different approach involving a repeat-inoculation test which was developed for application to cosmetics and toiletries and where the results were compared with preservative performance of manufactured products.
