Some widely used drugs alter the population of microbes in the gut, and a number raise the risk of antibiotic resistance, a new Dutch study shows.

The gut microbiome includes at least 1,000 species of bacteria and is influenced by a number of different factors, including medication. Research suggests that changes in the gut microbiome are associated with obesity, diabetes, liver diseases, cancer and neurodegenerative diseases.

“We already know that the efficiency and the toxicity of certain drugs are influenced by the bacterial composition of the gastrointestinal tract and that the gut microbiota has been related to multiple health conditions; therefore, it is crucial to understand which are the consequences of medication use in the gut microbiome,” said lead researcher Arnau Vich Vila, from the University Medical Center Groningen.

In this study, the researchers examined 41 commonly used drug categories and assessed 1,883 fecal samples from people who did and didn’t take the drugs, including some with irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).

Eighteen of the drug categories had major effects on the gut microbiome, and eight increased the risk of antimicrobial resistance.

The categories with the biggest impact on the microbiome were:

  • Proton pump inhibitors (PPIs), used to treat indigestion, peptic ulcer, H. pylori eradication, gastro reflux and Barrett’s esophagus.
  • Metformin, used to treat type 2 diabetes.
  • Antibiotics, used to treat bacterial infections.
  • Laxatives, used to treat and prevent constipation.

The gut microbiomes of PPI users had higher levels of upper gastrointestinal tract bacteria and increased fatty acid production, and metformin users had higher levels of potentially harmful E. coli bacteria.

Seven other drug categories were associated with significant changes in bacterial populations in the gut, according to the researchers.

For example, the use of SSRI antidepressants by people with IBS was associated with increased levels of the potentially harmful bacteria species Eubacterium ramulus.

Meanwhile, the use of oral steroids was associated with high levels of methanogenic bacteria linked with obesity and an increase in body mass index (an estimate of body fat based on weight and height).

The study was to be presented Wednesday at the UEG (United European Gastroenterology) annual meeting, in Barcelona. Such research is considered preliminary until published in a peer-reviewed journal.

“Our work highlights the importance of considering the role of the gut microbiota when designing treatments and also points to new hypotheses that could explain certain side-effects associated with medication use,” Vila said in a meeting news release.

More information

The American Gastroenterological Association has more on the gut microbiome.

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