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  1. Regulatory Science in Action

Prescription drug promotion in online character space limited (CSL) communications

Research by CDER investigators seeks to improve our understanding of the potential tradeoffs involved in promoting drugs using online character space limited communications.

The Federal Food, Drug, and Cosmetic Act and FDA’s regulations for prescription drug labeling and advertising include requirements for both the content and the prominence of risk information in promotional communications. The rise of online communications that have character space limitations, such as tweets and Google sponsored links, has led to questions about how to use these communications for prescription drug promotion while complying with applicable requirements for risk information. In 2014, FDA released the draft guidance for industry Internet/Social Media Platforms with Character Space Limitations — Presenting Risk and Benefit Information for Prescription Drugs and Medical Devices, which states:

“Regardless of character space constraints that may be present on certain Internet/social media platforms, if a firm chooses to make a product benefit claim, the firm should also incorporate risk information within the same character space limited communication. The firm should also provide a mechanism to allow direct access to a more complete discussion of the risks associated with its product.”

Because space is limited, some stakeholders have suggested that including a link to risk information in these communications may be sufficient. To address this question and others related to how these communications are presented, researchers in CDER’s Office of Prescription Drug Promotion (OPDP), within the Office of Medical policy, recently completed a study with the primary objectives of examining the effects of (1) including substantive risk information in the CSL communication itself versus only providing a link to risk information, and (2) including both risks and benefits versus describing only risks on the landing page to which the promotional communication links.

OPDP conducted four experimental studies (N=469 per study) to examine these questions. Participants who self-reported migraine (Studies 1 and 2) or being overweight (Studies 3 and 4) viewed a mock Google (Studies 1 and 3) or Twitter (Studies 2 and 4) search page. In each study, the researchers randomly assigned whether (1) the CSL communication (a tweet or Google sponsored link) included substantive risk information (see examples in Figure 1), (2) the landing page included benefit information, and (3) participants were instructed to browse the search page or instructed to search for information on the search page. Half the participants used a mobile device and half used a desktop or laptop computer. Participants viewed the search page twice: once without prompting to pay attention to the CSL communication and a second time with prompting.

Examples of the character-space-limited (CSL) communications used in the studies
Figure 1. Examples of the character-space-limited (CSL) communications used in the studies. OPDP researchers created mock CSL communications for each study. This figure shows the CSL communications (tweets) for a fictitious prescription drug for migraine.

Although the majority of participants across studies said they noticed the CSL communication, few clicked the link to additional information about the product the first time they saw it. Participants were more likely to recognize the substantial risk information after the first viewing if the substantial risk information was included in the CSL communication itself. However, the findings from the second viewing, when participants’ attention was focused on the CSL communication due to the instructions they received, add a potential caveat: if people are explicitly looking for information about the drug by reading the CSL communication, they may be less likely to click a link for further risk information if there is a substantial risk included in the CSL communication. Including the drug’s benefits on the landing page increased benefit recognition in all four studies, and in three of the four studies, benefit information on the landing page did not negatively affect participants’ recognition or perceptions of the risk information. The results provide a first look at the tradeoffs for consumer understanding of drug risks and benefits when drugs are promoted in CSL communications.

How has this work advanced the public’s health?
CDER researchers in OPDP and their collaborators are developing and applying rigorous experimental methods to advance our understanding of how consumers and healthcare providers perceive and respond to prescription drug promotion. The insights gained by this research can help inform guidance, enhance review of drug promotion, and ultimately help ensure that consumers and healthcare providers have the information they need to make informed health decisions.

Learn more about this study.






Device Type

Risk location

Risk-and-benefit landing page

Risk-only landing page

Risk-and- benefit landing page

Risk-only landing page


In CSL communication





On landing page only





Desktop/laptop computers

In CSL communication





On landing page only





Figure 2. Study design. Participants were randomly assigned to risk location, goal, and landing page conditions. Participants chose whether to participate on a mobile device or a computer.

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