The therapeutic efficacy of quercetin in combination with antiviral drugs in hospitalized COVID-19 patients: A randomized controlled trial

Eur J Pharmacol. 2022 Jan 5:914:174615. doi: 10.1016/j.ejphar.2021.174615. Epub 2021 Dec 2.


In this study, the therapeutic efficacy of quercetin in combination with remdesivir and favipiravir, were evaluated in severe hospitalized COVID-19 patients. Our main objective was to assess the ability of quercetin for preventing the progression of the disease into critical phase, and reducing the levels of inflammatory markers related to SARS-Cov-2 pathogenesis. Through an open-label clinical trial, 60 severe cases were randomly divided into control and intervention groups. During a 7-day period, patients in the control group received antivirals, i.e., remdesivir or favipiravir, while the intervention group was treated with 1000 mg of quercetin daily in addition to the antiviral drugs. According to the results, taking quercetin was significantly associated with partial earlier discharge and reduced serum levels of ALP, q-CRP, and LDH in the intervention group. Furthermore, although the values were in normal range, the statistical outputs showed significant increase in hemoglobin level and respiratory rate in patients who were taking quercetin. Based on our observations, quercetin is safe and effective in lowering the serum levels of ALP, q-CRP, and LDH as critical markers involved in COVID-19 severity. However, according to the non-significant borderline results in comparing the mortality, the ICU-admission rate, and the duration of ICU-admission, further studies can be helpful to compensate the limitations of our study and clarify the therapeutic potential of quercetin in COVID-19 treatments.

Keywords: COVID-19; Favipiravir; Quercetin; Remdesivir.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adenosine Monophosphate / administration & dosage
  • Adenosine Monophosphate / adverse effects
  • Adenosine Monophosphate / analogs & derivatives*
  • Alanine / administration & dosage
  • Alanine / adverse effects
  • Alanine / analogs & derivatives*
  • Amides* / administration & dosage
  • Amides* / adverse effects
  • Antioxidants / administration & dosage
  • Antioxidants / adverse effects
  • Antiviral Agents / administration & dosage
  • Antiviral Agents / adverse effects
  • Biomarkers / blood
  • COVID-19 Drug Treatment*
  • COVID-19* / diagnosis
  • COVID-19* / immunology
  • COVID-19* / mortality
  • Drug Monitoring / methods
  • Drug Monitoring / statistics & numerical data
  • Female
  • Hemoglobins / analysis
  • Humans
  • Male
  • Middle Aged
  • Outcome and Process Assessment, Health Care
  • Patient Discharge / statistics & numerical data
  • Pyrazines* / administration & dosage
  • Pyrazines* / adverse effects
  • Quercetin* / administration & dosage
  • Quercetin* / adverse effects
  • Respiratory Rate / drug effects


  • Amides
  • Antioxidants
  • Antiviral Agents
  • Biomarkers
  • Hemoglobins
  • Pyrazines
  • remdesivir
  • Adenosine Monophosphate
  • Quercetin
  • favipiravir
  • Alanine