Open-source online information channels have become increasingly important to the dissemination of medical information, including information about pharmaceuticals. We sought to determine the extent to which one prominent source of online information, Wikipedia, presented quantitative efficacy data about drugs. Using the Drugs@FDA website, we identified all new drugs approved by the Food and Drug Administration (FDA) from 1982 to 2020 and their associated Wikipedia pages, and used dummy variables to code for the presence of efficacy data, safety data, and usage data. Approximately 98% of 1201 drugs approved from 1982 to 2020 had Wikipedia pages. While most pages provided indirect indicia of efficacy, such as indication (98%) or mechanism of action (86%), fewer (21%) quantified evidence of benefit. Wikipedia drug pages were associated with indicia of high impact, including a median of more than 23,000 annual page views. Wikipedia is an important source of information that has the potential to shape public views about drug efficacy, but the absence of quantitative efficacy information in most pages limits public understanding of the benefits that drugs actually offer.