When metabolyzed in the body, inactive compounds can produce a therapeutically active ingredient, called “prodrug”. Countries must determine whether the patent on the compound covers the prodrug, and the extent to which claims relating to certain compounds should also be allowed to include their prodrugs¹¹³.

¹¹³ In the UK, for instance, it was held that sales of hetacillin, an acetone adduct of ampicillin which was immediately hydrolized in the body to ampicillin, infringed the ampicillin patent, because it was “ampicillin in disguise” (Grubb, 1999, p. 211).