To be placed on the market, a generic one does not need to provide evidence of its effectiveness and its non-toxicity, since "the active principle has already been the subject of these studies at the request of authorisation for the placing on the market of the original drug," says the national Agency of the drug. But if the active principle must be strictly the same, the excipients may change. The wildcard must, therefore, in addition to the quality of its manufacture, to prove its bioequivalence with the brand medicine. That is to say, to show that administered at the same dose and by the same route, it behaves the same way in the body.

This bioequivalence is measured according to three parameters: the fraction of the active principle absorbed, the maximum concentration in the blood and time to obtain it ; they should vary in a proportion of less than plus or minus 20% (10% when it comes to a drug with a narrow therapeutic", ...