Anti-inflammatories, antipsychotics and cancer drugs are among a host of medications that might inadvertently slow the growth of gut bacteria.

Many antibiotics can upset digestion, but it has not been clear to what extent other types of drug affect the gut’s bacterial balance.

Athanasios Typas at the European Molecular Biology Laboratory in Heidelberg, Germany, and his colleagues tested the effect of 835 non-antibiotic drugs on 40 common gut bacteria. Roughly one-quarter of the drugs restrained the growth of at least one bacterium, and nearly 5% affected at least ten. The authors also found that patients taking these non-antibiotics often have side effects similar to those reported for antibiotics.

The menagerie of microbes living in the gut is essential to human health. Identifying the drugs that affect specific gut bacteria could help efforts to develop new drugs and reduce the side effects of existing drugs, the authors say.