Study: Taking common drugs linked to impaired microbiome health and increased risk of obesity and intestinal infections
11/25/2020 // Virgilio Marin // Views

Researchers from the University Medical Center Groningen and Maastricht University Medical Center in the Netherlands have found that 18 common drug categories can negatively impact the gut microbiome, the total population of microbes present in the gut and their collective genetic material.

Many of these drugs, such as the diabetes drug metformin and the antidepressant selective serotonin reuptake inhibitors (SSRIs), can disrupt the healthy balance of beneficial and harmful gut bacteria. This can increase a person’s risk of intestinal infections and other health problems, including obesity, according to the researchers.

The findings of the study appeared in the journal Nature Communications.

Commonly used drugs impair gut microbiome

The researchers focused on 41 commonly used drug categories and analyzed more than 1,800 fecal samples from patients with either inflammatory bowel disease or inflammatory bowel syndrome (IBS), as well as healthy individuals to examine the effect of single medication use and combined medication use on the gut microbiome.

After comparing the gut microbial profiles of drug users to non-drug users, the researchers found the following drug categories to have the biggest impact on the gut microbiome:

  • Proton pump inhibitors (PPIs), which are used to treat peptic ulcers, acid reflux, infection with the bacteria Helicobacter pylori, dyspepsia and Barrett’s esophagus
  • Metformin, which is used to treat Type 2 diabetes
  • Antibiotics
  • Laxatives

People who took PPIs have abundant bacteria in their upper gastrointestinal tract and produce large amounts of fatty acids, according to the researchers. Meanwhile, metformin users had high levels of Escherichia coli, which can cause bacterial infections such as bacterial pneumonia and urinary tract infection.


The researchers also found an association between significant gut microbial changes and seven other drug categories. For example, SSRIs are associated with higher levels of the potentially harmful bacteria Eubacterium ramulus in people with IBS, and oral steroids are associated with higher levels of methanogenic bacteria, which can contribute to obesity and weight gain. (Related: Researchers discover gut bacteria that can render some drugs ineffective.)

The authors said that while it’s well-known that drugs can affect the gut microbiome, their study is important in that it presents which drugs have what effect and helps explain many of the side effects felt by patients.

“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,” said first author Arnau Vich Vila of the Department of Gastroenterology and Hepatology and the Department of Genetics at Groningen.

Antidepressants alter gut microbiome

Another study shows that antidepressants and other psychiatric drugs can negatively affect the quantity and composition of the gut microbiome. Irish-based researchers administered seven groups of rats with normal or slightly elevated levels of individual psychopharmaceuticals, including the SSRIs fluoxetine and escitalopram, and the mood stabilizers lithium and valproate.

After four weeks, the researchers examined the gut microbiome of the rats and found that some drugs consistently affected the number of certain bacteria. For instance, escitalopram and fluoxetine significantly inhibited the growth of isolated strains of bacteria such as E. coli, and lithium and valproate increased the numbers of Clostridium and other bacteria.

According to lead researcher Sofia Cussotto of the University College Cork, the study is the first to demonstrate that psychotropic drugs can negatively impact the gut microbiome in animals. The researchers are planning to conduct another study on human participants to test their findings.

Read more studies about the harmful side effects of drugs at

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