Could your pills be making you ill?
Commonly used drugs such as antibiotics and laxatives may heighten the risk of intestinal infections, obesity and other conditions linked to the bacteria in the gut, according to the latest research.
A new study, presented at the largest and most prestigious conference on gastroenterology in Europe, has revealed that 18 commonly used drug categories extensively affect the bacteria living in the gut. Eight different categories of drugs were also found to increase antimicrobial resistance mechanisms in study participants.
Researchers found that the changes observed in the gut microbiota (the communities of microbes that live in the gut) as a result of these medications could increase the risk of intestinal infections, obesity and other serious conditions linked to the gut microbiota.
The cutting-edge Dutch research looked at 41 commonly used drug categories. It found that the categories with the biggest impact included proton pump inhibitors, which are used to treat conditions such as dyspepsia (indigestion), as well as antibiotics, laxatives and metformin, a medication used in the treatment of type 2 diabetes.
The research was presented at the recent conference in Barcelona of the United European Gastroenterology group, a professional non-profit organisation combining all the leading European medical specialists and national societies focusing on digestive health.
"We have been studying the role of the gut microbiota for the last few years in the context of health," explained lead researcher Dr Arnau Vich Vila, a computational biologist specialising in the study of human gut microbiota at the Department of Gastroenterology and Hepatology of the University Medical Centre of Groningen in the Netherlands.
"Our group is interested in inflammatory bowel disease.
"We noticed that many factors influence the composition of the gut microbiota and that diet is one of these factors.
"We focused on medication as it has been shown that the gut microbiota interacts with different drugs, and that it has an influence on the body's response to different medications or therapies.
"We wanted to investigate the effects of specific drugs on the microbiota, and we focused on four different types of medications.
"We found links between the medication and the changes in the gut microbiota," he said, adding that one of the most significant results arose from the group's research into the effects of proton inhibitors.
"When a patient took this type of medication we found bacteria in the gut that is normally not there," Dr Vich Vila recalled.
"This is not good because this new composition of bacteria in the gut is more like the bacterial composition that we see in certain disorders, such as gut infections."
What it means, he added, is that there needs to be an awareness, firstly that medications could potentially have this kind of negative effect and secondly that this effect could be driven by the interaction between the gut microbiota and the medication.
"Some proton inhibitors can be bought in the supermarket or the pharmacy without prescription, so people should be aware that they use this medication on the advice of their doctor."
Doctors too, he emphasised, needed to consider whether such therapies were needed and also when to stop the treatment "because they may not be aware of these effects, which we are only now discovering."
More attention also needed to be paid to the gut microbiota by the pharmaceutical sector, he declared.
However, Dr Vila emphasised, more studies needed to be carried out. He said: "We have to be careful with interpreting this result. It's still early-stage research, but it's building on previous research in the same area so I think there's some consistency in what we are seeing.
"However, we have to be careful about drawing conclusions as further research needs to be carried out."
The findings have significant implications for our knowledge about the totality of the effects that drugs have on patients, observed Dr Niall Hyland, senior lecturer in the Department of Physiology at UCC and a faculty member at APC Microbiome Ireland.
It is an internationally renowned facility in Cork that investigates the behaviour of the microbiota, or the human gastrointestinal bacterial community.
"This research has major implications, because what it is beginning to reveal to us is the effect that drugs have on patients beyond what we expect them to have.
"Science was already aware that antibiotics target bacteria, which means they help treat infection," he said.
"However, now this latest study seems to suggest that other drugs, which we might not associate with having an effect on bacteria in the body, actually affect them."
There was now a possibility, he warned, that when we take other drugs to treat different conditions - drugs which, without our knowledge up to now, were possibly affecting bacteria in the gut - it could potentially contribute to the increasing problem of antibiotic resistance.
However, there was a positive to all of this, he added. Scientists were constantly searching for new antibiotics, so if some drugs previously believed to be non-antibiotic in nature, actually did prove to have antibiotic microbial properties, it could help researchers identify new anti-microbial strategies.
Some drugs traditionally used to treat psychiatric disorders, for example, have been found to act like antibiotics, killing the microbes in the gut, explained Dr Ger Clarke, lecturer in the Department of Psychiatry and Neuro-behavioural Science at UCC, and a faculty member of APC Microbiome Ireland.
"It is only really now that there is momentum in this area. There has been work done here in UCC showing that drugs which are commonly used, like anti-depressants and anti-psychotics, could kill certain bacteria.
"We also found they changed the composition of gut microbiota in rodents," he said, adding that some years ago a scientist at APC Microbiome Ireland investigated the effects of an anti-psychotic drug used to treat schizophrenia.
"This drug caused a lot of weight-gain in patients. But the research found that the drug changed the microbiota into a state that was likely to promote weight-gain.
"Some of the effects we experience in the use of drugs in psychiatry could be down to the effects they're having on our gut microbes.
"Now there is a lot of research ongoing, involving the testing of drugs for antibiotic-like properties. This is an area that is really coming to the fore and has a lot of momentum."
Dr Hyland said that some of APC Microbiome's work in other studies has shown that probiotics and prebiotics can affect the way the body metabolises drugs. "This is something that people need to think about when they are prescribing a medication for a patient."
For example, he said, a GP might need to ask if a patient was taking probiotics or prebiotics because these may affect the way they respond to a drug.
"If an elderly person is taking a number of different drugs - for example, antibiotics, medication for obesity and a laxative - it is worth considering whether the combined effect of these medications on the gut microbiota could account for any side effects the patient may experience. This is a very new and evolving area."
Scientists, said Dr Hyland, had always thought about drug interaction "in terms of how our body as a whole reacts, without giving due consideration to how the bacteria in our gut contribute".
Anyone involved in drug development would now have to consider how a new drug interacts with the gut microbiota, he explained.
Essentially, scientists must go back and work out exactly what happens when a patient takes a drug, said Dr Clarke.
"What I would have traditionally taught students is that there is a clinical pathway from the prescription of the drug to the patient response.
"In other words, how a drug acts depends on how the body processes the drug and what impact the drug has on its site of action, for example the brain or another organ.
"Within that framework we have routinely thought about our gut microbes. However, when you think about it, most drugs are taken orally so the first things it encounters are the bugs in the gut - so we really do need to think about the interaction between bugs and drugs."