Test systems to identify reproductive toxicants

Experience with drugs and other xenobiotics indicates that both animal test ing and epidemiological studies are necessary to provide adequate data for an estimation of risks that might be associated with exposure to a chemical substance. In this review, the pros and cons of test systems for reproduct ive toxicity are discussed. Usually, several studies are performed to cover the different phases of the reproductive cycle. In the preclinical develop ment of drugs, the three so-called 'segment testing protocols' have been us ed for several decades now. More recently, new testing concepts have been a ccepted internationally which include more flexibility in implementation. S everal examples of compounds with the potential for reproductive toxicity a re presented in more detail in a discussion of some pitfalls of the tests f or fertility (phthalates and fluoroquinolones), teratogenicity (aciclovir a nd protease inhibitors) and postnatal developmental toxicity (fluoroquinolo nes), In addition, important aspects of kinetics and metabolism as a prereq uisite for a rational interpretation of results from toxicological studies are briefly discussed. In vitro assays are useful for supplementing the rou tinely used in vivo approaches or for studying an expected or defined effec t, but they are not suitable for revealing an unknown effect of a chemical on the complex reproductive process.