Here’s yet another reason why all of us need to be careful when seeking health information online: Safety warnings about prescription drugs may be out of date.

That’s the finding of a study published last week in the New England Journal of Medicine (NEJM).

For the study, a team of Harvard University researchers looked at 22 drug-safety warnings issued by the U.S. Food and Drug Administration (FDA) between January 1, 2011, and December 31, 2012, for a variety of diseases, including high blood pressure, leukemia and hepatitis C. They then examined both the accuracy and the timeliness of references to those drugs on Wikipedia for 60 days before and after the FDA announcements.

Wikipedia is the single leading source of health care information in the United States, according to the IMS Institute for Healthcare Informatics. The 100 top health-related English-language Wikipedia pages were viewed an average of 1.9 million times over the past year, and a strong correlation exists between page views and the use of particular prescription drugs.

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The IMS Health report also found that half of all physicians say they have turned to Wikipedia for information on various medical matters.

Anyone with Internet access can write and/or edit most Wikipedia entries, and tens of thousands of volunteers do so each year.

Wikipedia slow to respond

For the current NEJM study, the researchers found that, collectively, the 22 drugs triggered 13 million Google searches and 5 million Wikipedia page views during the period of the study. Not surprisingly, the data also revealed that those searches and page views spiked immediately after the FDA issued a safety warning. Google searches for the drugs increased 82 percent, on average, in the week after each announcement, and Wikipedia page-views increased 175 percent, on average, on the day of the announcement.

But did those consumers who went online find accurate information on the drug’s safety? Many times not, for the study also made the following findings:

Only 41 percent of the Wikipedia pages were updated with the new safety warning within two weeks of the FDA’s announcement.

Another 23 percent of the pages took more than two weeks to update (average length of time: 42 days).

Some 36 percent of the pages remained unchanged more than a year later.

Some drugs more likely to be updated than others

The researchers also found that commonly prescribed prescription drugs — those use to treat at least 1 million people in the United States — were significantly more likely to be updated within two weeks than less commonly prescribed drugs (58 percent vs. 20 percent).

As an example, the researchers point to the drug brentuximab vedotin (Adcetris), which is used to treat Hodgkin lymphoma. In January 2012, the FDA issued a black-box label warning that the drug had been linked to two cases of progressive multifocal leukoencephalopathy, a virus-caused neurological condition that can be a life-threatening for people with weakened immune systems. In the week after the warning, Google searches for the drug increased 50 percent, and Wikipedia page-views increased 141 percent.

“However,” write the researchers, “there was still no mention of the new black-box warning on Wikipedia 2 years later, a discrepancy that substantiates concerns raised by previous studies over the reliability of online drug information.”

Implications

The findings from the NEJM study have serious implications. A 2012 survey by the Pew Internet Project found that 72 percent of the 81 percent of Americans who use the Internet sought health information online, mostly through search engines such as Google or through websites such as Wikipedia. The study also found that 59 percent of those people were using the sites to determine whether or not symptoms they were having were something to worry about.

That’s 35 percent of all U.S. adults.

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If updated drug-safety warnings are not found on those sites, the patients may not connect their symptoms to an adverse drug reaction and may therefore delay seeking medical care.

The Harvard researchers recommend that the FDA improve consumer access to drug information by making its own website more consumer-friendly and by making better use of social media.

They also encourage more projects like one at the University of California, San Francisco, which offers academic credit to medical-school students who edit medical content on Wikipedia.

In the meantime, consumers who want the latest information about a prescription drug should make their first stop the FDA’s MedWatch site.

And, of course, talk with your doctor — although you may want to ask your doctor the source of his or her drug-safety information.

You can read the NEJM study on the journal’s website.