1) Patients with hypersensitivity for tetracycline compound2) Patients showing SpO2 < 93% without oxygen inhalation3) Patients who are or have a possibility to be pregnant, or hope to be pregnant during the study.4) Patients with liver failure (AST and/or ALT >= the standard value)5) Patients with kidney failure (eGFR < 30 ml/min/1.73m2)6) Patients who had a COVID-19 vaccination7) Patients who are considered unsuitable for the study by the PI or sub investigators

1) Patients with hypersensitivity for tetracycline compound2) Patients showing SpO2 < 93% without oxygen inhalation3) Patients who are or have a possibility to be pregnant, or hope to be pregnant during the study.4) Patients with liver failure (AST and/or ALT >= the standard value)5) Patients with kidney failure (eGFR < 30 ml/min/1.73m2)6) Patients who had a COVID-19 vaccination7) Patients who are considered unsuitable for the study by the PI or sub investigators

1) Patients with hypersensitivity for tetracycline compound2) Patients showing SpO2 < 93% without oxygen inhalation3) Patients who are or have a possibility to be pregnant, or hope to be pregnant during the study.4) Patients with liver failure (AST and/or ALT >= the standard value)5) Patients with kidney failure (eGFR < 30 ml/min/1.73m2)6) Patients who are considered unsuitable for the study by the PI or sub investigators

1) Patients with hypersensitivity for tetracycline compound2) Patients showing SpO2 < 93% without oxygen inhalation3) Patients who are or have a possibility to be pregnant, or hope to be pregnant during the study.4) Patients with liver failure (AST and/or ALT >= the standard value)5) Patients with kidney failure (eGFR < 30 ml/min/1.73m2)6) Patients who are considered unsuitable for the study by the PI or sub investigators

1) Patients with hypersensitivity for tetracycline compound2) Patients showing SpO2 < 93% without oxygen inhalation3) Patients who are or have a possibility to be pregnant, or hope to be pregnant during the study.4) Patients with liver failure (AST and/or ALT >= the standard value)5) Patients with kidney failure (eGFR < 30 ml/min/1.73m2)6) Patients having history of gout or currently receiving treatment of gout or hyperuricemia7) Patients who are considered unsuitable for the study by the PI or sub investigators

1) Patients with hypersensitivity for tetracycline compound2) Patients showing SpO2 < 93% without oxygen inhalation3) Patients who are or have a possibility to be pregnant, or hope to be pregnant during the study.4) Patients with liver failure (AST and/or ALT >= the standard value)5) Patients with kidney failure (eGFR < 30 ml/min/1.73m2)6) Patients having history of gout or currently receiving treatment of gout or hyperuricemia7) Patients who are considered unsuitable for the study by the PI or sub investigators