Nexium, manufactured and marketed by AstraZeneca, is a prescription heartburn medication, which was advertised as being more effective than Prilosec in clinical trials. However, those trials were misleading because they involved testing of Nexium at twice the level of Prilosec. At the time of the Nexium marketing campaign, AstraZeneca's patent on Prilosec was about to expire. The company marketed Nexium as more effective than Prilosec in order to boost sales of Nexium, which actually contained the same active ingredient and had a very similar molecular structure to Prilosec. Several lawsuits claim that the drug maker duped consumers into buying essentially the same drug at a much higher price.