Despite tremendous efforts to ensure the safety and effectiveness of newly marketed medications, a number of these have had significant problems after introduction of the drug to the market. Such problems highlight the practical limitations of clinical trials performed to obtain FDA approval for marketing. Pharmacoepidemiology research methodologies provide a powerful mechanism for exploring the determinants of drug safety and effectiveness in broad-based populations and can serve as a scientific foundation for outcome research. Using these methodologies, largescale postmarketing surveillance studies similar to the type described in the accompanying articles would constitute an important way of confirming and identifying the determinants of drug safety and effectiveness in large, diverse patient populations.

By Thaddeus H Grasela, Watkins WD, Hug CC Jr, McLeskey CH, Nahrwold ML, Roizen MF, Stanley TH, Thisted RA, Cynthia Walawander, White PF