What is the significance of the impact of antipsychotics on the gut microbiome?

A healthy balance among the many life forms that inhabit the human gut is vital not only to our gastrointestinal system but also to all our important physiological systems – the central and autonomic nervous system, the immune system, and the endocrine system. These disparate networks influence each other in multiple reciprocal ways. This commentary focuses on one specific aspect of these interconnections – how a class of therapeutic drugs, the antipsychotics (AP), affects the gut microbiome, and how that effect, in turn, influences AP efficacy and tolerability. AP drugs are the gold standard treatment for schizophrenia and are prescribed for all psychotic disorders (delusional disorder, depression, or mania with psychotic features, schizoaffective disorder, metabolic, or neurologic or toxic disorders that result in psychotic symptoms, such as delusions and hallucinations). Sometimes, at relatively low doses, AP are also prescribed for more everyday conditions, such as insomnia, severe anxiety, emotional trauma, eating disorders, or aggression. The gut microbiome is significantly impacted by these drugs, especially when they are taken orally. This is because many of the main indications for AP treatment require lifelong and relatively high daily drug doses. AP influence in the gut can, therefore, be substantial, prolonged, and cumulative [1]. While these influences pertain to treatment via the mouth and gastrointestinal system, AP does not need to be given orally. They can be administered through other routes, one of the most effective being monthly intramuscular injections that avoid first-pass metabolism through the liver and leave gut microbiota comparatively unchanged. Giving pills by mouth is the current clinical routine, although it has become evident that nurse-administered injections at regular time intervals are safe and effective. Such administration overcomes the problems of forgetfulness, deliberate non-adherence, and intentional overdose. Long-acting injections have been shown to result in better outcomes than orally taken drugs [2].