Within the epidemic context of phase 3 in Mexico, the implementation of new treatments that have been shown to be beneficial for patients in other countries is an urgent need. Methylene blue (MB, the oxidized form, blue color) has been used in many different clinical medicine areas, ranging from malaria to orthopedics. Methylene blue absorbs energy directly from a light source and then transfers this energy to molecules of oxygen creating singlet oxygen (O2), which is the first electronic excited state of molecular oxygen (O2). Singlet oxygen is extremely electrophilic; thus, it can directly oxidize electron-rich double bonds in biological molecules and macromolecules. For this reason, methylene blue has been used as a photosensitizer in the treatment of cancer and the protection of serum from viral agents. Methylene blue can be reactivated using energy from a light source in the body until processed out through the kidneys.

Patients diagnosed with COVID-19 and confirmed positive with the virus by PCR will be treated with Prexablu for seven days. The administration is Sublingual 1 ml Prexablu once a day and PDT for 1 hour daily x 7 days. Days to clinical improvement to be evaluated for seven days considering temperature and other vital signs measurement, arterial oxygen saturation.

I. On day one and day seven a blood sample will be drawn to assess chemistry (including liver function tests), C reactive protein, IgG, IgM, IL-6, erythrocyte sedimentation rates like procalcitonin, ferritin levels, and the D dimer II. Daily PCR Swabs measuring cycle threshold (CT) will be collected (days 1 - 7) III. Daily 1ml Prexablu will be placed sublingual

1. Prexablu activated for 10 minutes with Low Level Light Therapy (670 nm light) before being placed sublingually.
2. Low Level Light Therapy (NocUlite device) will be placed on wrist for 50 minutes.

Inclusion Criteria:

• Patients over 18 years of age
• Of both sexes
• Confirmed case of Covid-19 (by RT-PCR) and CT less than 32 in the E
• That they go to the ER service due to COVID symptoms, and that they voluntarily agree to participate in the study by written the informed consent
• With at least 1 of the following symptoms: fever, headache, nausea, dyspnea, myalgia, vomiting, or diarrhea
• With chest X-ray without pneumonia criteria
• With SO2> 90
• No history of allergic reaction to methylene blue
• No history of treatment with medication with methylene blue negative interaction

Exclusion Criteria:

• Pregnancy and breastfeeding
• Preadmission anticoagulation
• Severe renal insufficiency (glomerular filtration rate <30 mL/min/1.73m2)
• Active chronic hepatitis
• Patients with history of allergic reaction or significant sensitivity to methylene blue
• Treatment with immunosuppressive agents
• Diagnosis of cancer at any stage and of any type.
• Pregnancy and breastfeeding
• Patients who plan to become pregnant during the study period or within 6 months after the end of the study period.
• Participation in another clinical trial with an experimental drug in the last 30 days.
• Other pathologies that, in the medical opinion, contraindicate participation in the study.
• Uncompensated comorbidities