The Weber Effect and the United States Food and Drug Administration’s Adverse Event Reporting System (FAERS): Analysis of Sixty-Two Drugs Approved from 2006 to 2010

BACKGROUND: The United States Food and Drug Administration's (FDA) Adverse Event Reporting System (FAERS) consists of adverse event (AE) reports linked to approved drugs. The database is widely used to support post-marketing safety surveillance programs. Sometimes cited as a limitation to the usefulness of FAERS, however, is the 'Weber effect,' which is often summarized by stating that AE reporting peaks at the end of the second year after a regulatory authority approves a drug. Weber described this effect in 1984 based upon a single class of medications prescribed in the United Kingdom. Since that time, the FDA has made a concerted effort to improve both reporting and the database itself. Both volume and quality of AE reporting has dramatically improved since Weber's report, with an estimated 800,000 yearly reports now being logged into FAERS. OBJECTIVE: The aim of this study was to determine if current FAERS reporting follows the trend described by Weber. METHODS: Sixty-two drugs approved by the FDA between 2006 and 2010 were included in this analysis. Publicly available FAERS data were used to assess the 'primary suspect' AE reporting pattern for up to a 4-year period following each drug's approval date. RESULTS: A total of 334,984 AE reports were logged into FAERS for the 62 drugs analyzed here. While a few of the drugs demonstrated what could be considered 'Weber effect' curves, a majority of the drugs showed little evidence for the effect. In fact, the general AE reporting pattern observed in this study appears to consist simply of increasing case counts over the first three quarters after approval followed by relatively constant counts thereafter. CONCLUSIONS: Our results suggest that most of the modern adverse event reporting into FAERS does not follow the pattern described by Weber. Factors that may have contributed to this finding include large increases in the volume of AE reports since the Weber effect was described, as well as a concerted effort by the FDA to increase awareness regarding the utility of post-marketing AE reporting.