Some ingredients labeled as inactive may actually interact with a drug's biological target, according to a recent study published July 24 in Science.
Inactive ingredients usually add preservatives, fillers or color. The study, conducted by researchers from the University of California San Francisco and the Novartis Institutes for BioMedical Research, used machine learning to screen 600 of these additives against 3,000 targets.
The researchers found that 38 approved inactive ingredients exhibited 134 previously unforeseen activities against biological targets. Five of these ingredients showed signs of possible toxicity on the tissue level, and research suggests that two of them — thimerosal and cetylpyridinium — could potentially rise to potent levels in the body.
The study did not indicate what side effects these biological reactions may cause.