Kami-kihi-to for COVID-19

Coronavirus disease 2019 (COVID-19) remains a global threat to human health because of its sporadic prevalence despite the development of COVID-19 vaccines and several drugs such as remdesivir and molnupiravir. Moreover, long COVID has become another global issue. No standard treatment has been established for long COVID. Therefore, finding quickly effective and low-priced drugs against COVID-19 and long COVID-19 and conducting clinical trials on these drugs remains crucial for global health. Drug repurposing is a well-known strategy for redeploying existing licensed drugs for newer indications, enabling the shortest possible transition from bench to bed side. Regarding existing licensed drugs for COVID-19, tetracycline has been administered since the beginning of 2020 due to its efficacy in inhibiting COVID-19 and its anti-inflammatory effects. Neuroinflammation associated with microglia in the central nervous system is considered one of the pathophysiologies of long COVID. Further, tetracycline is expected to be efficacious against long COVID because it inhibits microglial activity. Recently, minocycline has been efficacious against long COVID. Considering other existing licensed drugs for COVID-19, Kampo medicine, which is a traditional Japanese medicine, has been prescribed during the COVID-19 pandemic due to its efficacy in inhibiting severe acute respiratory syndrome corona virus 2 and its anti-inflammatory effects. Recently, Kampo medicine has been effective for long COVID. Multidrug treatment is effective because of the synergistic effects associated with the different mechanisms of action of the concerned drugs. Therefore, a combination of minocycline and Kampo medicine may be more efficacious against COVID-19 and long COVID.