title: Importance and challenges of studying marketed drugs: what is a phase IV study? Common clinical research designs, registries, and self-reporting systems.
abstract: The new drug application database submitted to the US Food and Drug Administration for drug approval (phases I-III or phases 1-3) is limited both in scope and size. Although randomized controlled trials, the hallmark of phase III trials, are the gold standard for the drug-approval process, they invariably have a number of limitations, including relatively small sample sizes, selective populations, short follow-up, the use of intermediate (surrogate) endpoints (almost always), and limited generalizability. The challenges of monitoring drugs once approved are also numerous. After approval by the Food and Drug Administration, marketed drugs undergo continued scrutiny, and this scrutiny is increasing because of problems that have surfaced with some drugs after their approval. Postmarketing research includes a variety of study designs and the use of registries and self-reporting of drug side effects. Along with this has come great confusion about what postmarketing research is and what a phase IV study is. Among the important strengths of phase IV research are the exposure of a broader range of patients to the drug under study, resulting in more "real-world" information about the drug's safety and efficacy, and consideration of a broader range of clinical endpoints. As a result, phase IV, or postmarketing research, has become an integral part of the drug evaluation process for a wide range of agents. The authors discuss the different types of study designs that are common under the phase IV terminology and provide some examples. They also discuss the use of registries and self-reporting of adverse events using the MedWatch System.
authors.affiliation: University of Alabama at Birmingham, Division of Prev. Medicine, 1717 11th Ave S, MT638, Birmingham, AL 35205-4731, USA.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Glasser
authors.forename: Maribel
authors.initials: M
authors.lastname: Salas
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Delzell
mesh_terms: D016907:Adverse Drug Reaction Reporting Systems; D017327:Clinical Trials, Phase IV as Topic / Q000379:methods*; D016208:Databases, Factual; D064420:Drug-Related Side Effects and Adverse Reactions; D006801:Humans; D011358:Product Surveillance, Postmarketing / Q000379:methods*; D012042:Registries; D012107:Research Design; D014481:United States; D014486:United States Food and Drug Administration