Beyond "Psychotropic": Repurposing Psychiatric Drugs for COVID-19, Alzheimer's Disease, and Cancer.

Importance: "Psychotropic" drugs have widespread reach and impact throughout the brain and body. Thus, many of these drugs could be repurposed for non-psychiatric indications of high public health impact. Observations: The selective serotonin reuptake inhibitor (SSRI) fluvoxamine was shown efficacious as a COVID-19 treatment based on randomized controlled trials (RCTs), and a benefit of other antidepressants has been posited based on observational and preclinical studies. In this review, we illuminate features of SSRIs and other psychiatric drugs that make them candidates to repurpose for non-psychiatric indications. We summarize research that led to fluvoxamine's use in COVID-19 and provide guidance on how to use it safely. We summarize studies suggestive of benefit of other antidepressants versus COVID-19 and long COVID. We also describe putative mechanisms of psychiatric drugs in treating long COVID, Alzheimer's disease, cancer, and other conditions. Conclusion and Relevance: There is a potentially great clinical and public health impact of psychotropic drug repurposing. Challenges exist to such repurposing efforts, but solutions exist for researchers, regulators, and funders that overcome these challenges.