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What’s in that pill you just swallowed?

The label on the bottle lists the drug’s active and inactive ingredients, but new research concludes some of those “inactive” ingredients aren’t so inactive. Whether these extra substances, in everything from ibuprofen to antihistamines to antacids, add color, preservatives, or fillers, some of them can also interact with a medication’s biological target. That could potentially cause side effects, though the study didn’t determine whether the ingredients in fact do so.


Researchers from the University of California, San Francisco, and the Novartis Institute for BioMedical Research deployed computational methods and cellular experiments to see how current drug formulations stack up in terms of any unintended biological effects from these inactive ingredients, known as excipients, in both prescription and over-the-counter drugs. Using machine learning, they screened 600 common excipients against 3,000 targets typically used to identify potentially harmful side effects. 

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