Most people stop thinking about a medicine once the treatment is finished and the packet disappears from the bathroom cabinet. But what happens inside the body may not end quite as quickly.
Research from scientists at the University of Tartu suggests that previous medication use could remain associated with the gut microbiome years later. The study was published in mSystems in 2025 and later highlighted by the Estonian Research Council, reports ScienceDaily.
Years later
The researchers used data from more than 2,500 Estonian Biobank participants, comparing prescription histories with information from stool samples.
Their analysis linked several types of medication to differences in the microorganisms living in the gut. For some drugs, these microbial patterns were detectable years after treatment had ended.
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The associations were not restricted to antibiotics. Antidepressants, beta-blockers, benzodiazepines and proton pump inhibitors were among the other medications identified.
Unexpected differences
Benzodiazepines stood out because their association with the microbiome was comparable to that observed with broad-spectrum antibiotics.
The researchers also found that medicines belonging to the same drug category did not necessarily show identical patterns. Diazepam and alprazolam, for example, were associated with different levels of disruption.
This distinction could matter when scientists investigate links between the microbiome, medication and disease.
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Medical history matters
A smaller group of participants provided follow-up samples, allowing researchers to examine what happened when certain medications were started or discontinued.
Those observations supported an association between medication use and changes in gut microbes.
Importantly, the findings do not establish that medicines taken years ago necessarily cause health problems today. Instead, the research highlights something scientists may need to consider when studying the microbiome: a person's previous medication history could influence what they find.
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This article is made and published by Mie Hermansen, who may have used AI in the preparation.