1,000 non-antibiotic drugs were tested against 40 representative gut bacterial strains and found that 24% of the drugs inhibited the growth of at least one bacterial strain in-vitro. These observations agree with the few clinical microbiome studies for which medication has been recorded to affect the gut microbiome.

Concentrations within the range of what is estimated to be found in the human gut for many drugs were used in this study; however, it was done in-vitro so more evidence is needed before conclusions can be made.