In vitro cytotoxicity tests for the prediction of acute toxicity in vivo

Investigations of the use of in vitro cytotoxicity tests for the prediction of acute toxicity in vivo have been reviewed with particular emphasis on those studies that have been published during the past 5 years. Numerous cell types, endpoints and exposure periods have been used in cytotoxicity tests, although these appear generally to have little effect on the resulting correlation between in vitro IC₅₀ values and in vivo LD₅₀ values. The in vitro data correlate better with rodent parenteral (ip or iv) LD₅₀ values than with oral LD₅₀ values due to kinetic considerations. For certain groups of related chemicals (e.g. antitumour compounds, metal salts), and for some sets of unrelated chemicals, the in vitro data correlate very well with LD₅₀ values. However, while cytotoxicity tests are useful for screening chemicals for their intrinsic and relative toxicities, it is impossible to tell whether predictions based on cytotoxicity data alone would be sufficiently accurate for labelling and classifying a new chemical according to its likely acute toxicity in vivo. The in vitro endpoints need to be of greater relevance to the possible mechanisms of chemically-induced acute toxicity in vivo than most of those that are used at present.