d to use animals for pre-screening of potential drug candidates. For example, TOPKAT is a mathematical computer model based on physical and chemical structures and properties of a substance (10). This replacement procedure is used to determine the oral toxicity and possible skin and eye irritancy of a substance. The TOPKAT test is currently 75 to 100% accurate, and is regularly used by the Food and Drug Administration, the Environmental Protection Agency, and the United States Army. Computer simulations and multi-media presentations are often used to replace the use of animals for education purposes. Even though these simulations are available, it is very difficult, and in many cases still not possible, to simulate a hands-on experimental situation. In order to improve upon these programs, a huge amount of data from mostly in vivo studies has to be collected and applied to the programs.Physicochemical data, pH for example, are used in combination with structure-activity relationships to predict the biological effects of chemicals. One product, the Irritection Ocular Assay System, formerly known as Eytex or Skintex, uses a solution that is made up of proteins, glycoproteins, lipids, and low molecular weight components that self-associate to form a complex molecular matrix. The test works by mimicking the reaction of the cornea and human skin when exposed to a foreign substance. If a chemical has a potential to irritate the eye, then it will cause the solution to coagulate. At the present time, the test can determine the toxicity of over 5000 different materials (8). Many cosmetic companies, such as Avon, use this system to screen potential irritants without testing them on animals.Sometimes it is possible to conduct studies in lower organisms, such as invertebrates, plants and microorganisms, or in vertebrates at early stages of development. Some examples of this type of alternative are the Ames test and the LAL test. The Am...
