Inactive ingredients may not be so inactive

Most medications have two main components: The active compounds, and then “inactive ingredients” that add color, preservatives, or serve as fillers. Catch is, these ingredients aren’t always so inactive, a new study finds.

UCSF researchers teamed up with Novartis’ biomedical research arm used machine learning to screen 600 inactive ingredients, and found that 38 act on physiologically relevant targets in unforeseen ways, STAT’s Elizabeth Cooney writes. Five ingredients showed potential toxicity, and two — thimerosal and cetylpyridinium — could reach potent levels in the bloodstream.

Such substances are not just confined to medicines: They can be found in food additives like the sweetener aspartame, and show up in food and drinks in higher levels than they do in drugs.