The recent withdrawal of Cox-2 Inhibitors has generated debate on the role of information in drug diffusion: can the market learn the efficacy of new drugs, or does it depend solely on manufacturer advertising and FDA updates? In this study, we use a novel data set to study the role of learning in the diffusion of three Cox-2 Inhibitors—Celebrex, Vioxx and Bextra—before the Vioxx withdrawal. Our study has two unique features: first, we observe each patient’s reported satisfaction after consuming a drug.