Effect of Doxycycline on clinical improvement and outcome in patients with COVID-19

INTERVENTION: Intervention 1: Intervention group: In addition to the national standard protocol and supportive therapies, they are treated with doxycycline capsules manufactured by Pars Behroozan company at a dose of 200 mg first day and then 100 mg every 12 hours daily with two glasses of water in a sitting position for 7 days. Intervention 2: Control group: They are treated with standard protocol including daily oxygen with the rate of 5 to 7 liters per minute, observance of hygienic principles and subcutaneous heparin produced by Caspian Pharmaceutical Company, 5000 units three times per day for 10 days. CONDITION: B34.2 Covid 19. ; Coronavirus infection, unspecified PRIMARY OUTCOME: Duration of hospitalization. Timepoint: Before the intervention and 5 days after the intervention. Method of measurement: Checklist. ICU admission. Timepoint: Before the intervention and 5 days after the intervention. Method of measurement: Checklist. INCLUSION CRITERIA: Age higher than 18 years Definitive diagnosis of Covid 19 Having informed satisfaction