The severe acute respiratory syndrome caused by COVID-19 is now a global catastrophic event. Currently there is no approved drug or vaccine for the disease. Methylene blue (MB, oxidized form, blue color) has been used in many different areas of clinical medicine, ranging from malaria to orthopedics. Leucomethylene Blue (reduced form of MB, colorless) may be applied for the treatment of COVID-19 according to the scientific evidences.

Inclusion Criteria:

1. Confirmed case of Covid-19 (by RT-PCR, HRCT)
2. Admission to Intensive Care Unit
3. Need for intubation and mechanical ventilation (PaO2/FiO2 < 100-200)
4. Written informed consent

Exclusion Criteria:

1. Pregnancy and breastfeeding
2. History of G6PDH deficiency
3. Preadmission anticoagulation
4. Severe renal insufficiency (glomerular filtration rate <30 mL/min/1.73m2)
5. Medical records of cirrhosis
6. Active chronic hepatitis
7. Severe hepatic disease defined by GOT or GPT levels three times above the normal upper limit
8. Patients with history of allergic reaction or significant sensitivity to Methylene blue
9. Treatment with immunosuppressive agents
10. Use of other investigational drugs in the moment of inclusion