COVID-19, hydroxychloroquine and the importance of disease progression.

The COVID-19 pandemic struck swiftly and forcefully. The medical response both commercial and clinical achieved what it could with the resources it had. In addition, society changed old habits and developed new behavior patterns. It is appropriate to identify what lessons were learned from COVID-19 for the future. The most important observation for managing SARS-CoV-2 infections was the identification, but not necessarily appreciation, of the manner in which the virus acts over time in the host that it infects. Based on population densities, the ease with which people are mobile and the way that SARS-CoV-2 infected humans, other infectious diseases can easily become pandemics in the future. This review is not focused on a xenobiotic and its toxicant properties. Rather, the review describes the relationship between a therapeutic (hydroxychloroquine) and the progression of a disease (SARS-CoV-2) along with the timing and sequence of the various pathologies that the disease causes. While at first glance, this may appear to beyond the scope of toxicology, it is not. Toxicology is capable to address disease-induced pathologies because it can use the same skills and tools that it uses for pathologies that xenobiotics cause. Assessing the pathology caused by a disease concurrently with the pathology caused by the drug used to treat the disease, puts toxicology in a position to make a greater contribution to drug development. Repurposing toxicology, just as drugs were repurposed for the COVID-19 pandemic, will avoid missing or misusing a useful therapeutic agent just because the disease-initiated pathology was ignored or unappreciated.