Mice and rats constitute 99% of the experimental animals used in the Merck Group. Other animal species are only used when preliminary scientific testing and experience shows the results from experiments on rats and mice to be invalid. Legal regulations require drugs in development to be safety tested on a rodent species (rats or mice) and on a non-rodent species (dog, pig, monkey). In this way, potential side effects can be identified and included in the benefit-risk assessment of a substance prior to first-inman use. In all experiments, the safety of human beings is our top priority.
