In vitro models.

The development of in vitro models is advancing rapidly, with the application of cell culture methods as an alternative to animals in toxicological screening; non-cellular systems are also being used. Any screening test, whether for detecting irritants, carcinogens or teratogens should be well validated against known animal studies. It should, for example, be able to correctly identify a teratogen as well as a non-teratogen. Various types of in vitro systems are utilised. Some validated test systems have been used for several years to detect genotoxins and are acceptable to many regulatory authorities. This is not the case for other in vitro systems, although some for skin irritation and corrosion are acceptable to some authorities. A non-comprehensive range of tests to measure responses in ocular, immune, cardiac, vascular, neurological, sensory, hepatic, testicular and embryological systems are described. Some tests are empirical and others much more closely mimic the animal model they represent. Some of the methods described are much closer to validation than others.