There has been growing interest in the interaction between the gut microbiome (genes of gut bacteria) and medications. Some medications are known to effect the gut in certain ways. For example, antibiotics tend to change the amount and types of bacteria in the gut which can cause side effects such as nausea and diarrhea. The drugs associated with lowering stomach acids such as PPIs (protein pump inhibitors), is associated with an increase in oral bacteria (that’s right…bacteria that’s found in the mouth) and potential pathogenic bacteria in the gut. There are interactions between the gut microbiome and medications.
Researchers studied the effects of 15 drugs on 25 strains of human gut bacteria and found a variety of drug-bacteria interactions. Some bacteria store the drug without chemically changing it while other bacteria chemically modify it to make it more or less bioactive. In other words, the gut bacteria can determine the amount of a drug (or an active drug metabolite) that is available to the body.
The opposite is also true. A particular drug can also affect a patient’s gut bacteria, both the number and function of that bacteria. For example, the build-up of a drug within a strain of bacteria can change the growth rate of those bacteria. Sometimes a drug can even change the molecules that are secreted by bacteria. This doesn’t sound like a big deal until you understand that the molecules can include hormones, neurotransmitters and molecules of inflammation that effect our physiology. There are clearly interactions between the gut microbiome and medications.
The drug variability can be due to either a person’s genetics or due to the person’s gut flora. Association studies have shown changes in the abundance of various gut bacteria in individuals with inflammatory bowel disease, irritable bowel syndrome and colorectal cancer. This has also been found in other systemic diseases such as cardiovascular, metabolic conditions, autoimmune and psychiatric disorders.
As you can see here, there is a complex bidirectional interaction between commonly used drugs and the gut microbiome. This means that among people who have the same disease, a particular drug can vary greatly in its effectiveness and adverse effects. Perhaps this will help us in finding interventions to modulate the gut microbiome and optimize effectiveness of treatment.
Reference: Klünemann, M et al. Bioaccumulation of therapeutic drugs by human gut bacteria. Nature 2021 Sep; 597:533
Weersma, R et al. Interaction between drugs and the gut microbiome. Gut 2020 Volume 69, Issue 8. gut.bmj.com