When you buy some Tylenol or NyQuil, you probably know — or find out easily from looking at the label — that these products contain acetaminophen. But knowing the names of active ingredients in an over-the-counter drug isn’t the same as knowing how those ingredients will interact with other drugs or what could happen if you take too much. A new study looks at the apparent disconnect between reading a label and understanding the potentially dangerous implications of what you’re taking.

For the study, published in the Journal of Public Policy & Marketing, researchers from UCLA, UC Irvine, and Cal State Sacramento compared the average college undergrad’s understanding of OTC drugs with that of current nursing and medical students who presumably have some education on common drug ingredients and interactions.

The researchers hypothesized that the wide availability and ubiquitous advertisement of OTC drugs leaves many consumers with the impression that these products are relatively harmless. They cite a 2012 study that found that buyers of these drugs often believed they could determine on their own how much they should take, regardless of directions on the label.

But this naive attitude toward drugs can put the user at risk.

“A consumer who takes a cold medicine containing, for instance, acetaminophen, may see nothing wrong with taking an additional medicine that also contains acetaminophen,” write the study’s authors. “But in that case, he or she will likely ingest at least 1300 mg of acetaminophen, and if those doses are repeated every 4-6 hours, the consumer will take in at least 5200 mg of acetaminophen per day, well over the limit.”

Overuse of acetaminophen can result in damage to your liver and is particularly dangerous for small children.

The first test in the study was an open-ended thought task in which participants — one group of undergrad business majors, the other nursing students — were presented with common OTC drugs or brands and asked to write down the thoughts that came to mind. They were then asked a series of multiple choice questions about their knowledge of OTC drugs.

In terms of the multiple choice questions, it’s no surprise that the nursing students outperformed the others, with an average score nearly double that of the novice undergrads.

But the real difference between the two groups is highlighted when looking at the list of thoughts they jotted down. Nursing students were three times as more likely to write down the active ingredient and twice as likely to mention potential risk, though both groups seemed to have the same impression that OTC drugs are generally safe.

In a second test, subjects were shown retail packaging (front and back) of pairs of OTC drugs and asked to assess whether someone who had taken both drugs might be at risk. They were also asked to determine whether two paired products were similar.

“[N]ovices failed to use active ingredients as a diagnostic or relevant attribute when assessing the risk of taking two OTC drugs together, only experts did this,” reads the study. “Novices seemed to hold the naive belief that OTC drugs were relatively risk-free because they viewed double doses of the same active ingredient as about the same in terms of health risk as single doses of two different ingredients.”

What if you make the active ingredient more noticeable and prominent on the packaging through some sort of burst or icon?

A third test repeated the previous test but with more obvious displays of the main active ingredient in each product.

Alas, while the novice test subjects were indeed more readily able to identify when two products had similar or different ingredients, the more prominent labeling “was relatively ineffective on its own at improving risk assessments among novice consumers… Even after they saw the active ingredient icons, these consumers continued to naively believe that taking two OTC drugs with the same active ingredient was about as safe as taking two OTC drugs with different active ingredients.”

The researchers say their results suggest that merely calling out the active ingredients without providing context or education for the consumer may not have the desired effect. Perhaps drug labels need to be more explicit, not just in highlighting the active ingredients, but in more explicitly stating the importance of avoiding concurrent use of two similar drugs.

“Programs to educate the public on the risks of double-dosing must clearly emphasize that even over-the-counter medications can be dangerous when combined or misused,” write the researchers. “More broadly, this study suggests that it is vitally important for practitioners and policymakers to address safety issues by first working to understand what is at the root of the consumer’s misunderstanding.”

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