Abstract: medRxiv preprint doi: https://doi.org/10.1101/2021.03.03.21252509; this version posted March 5, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-ND 4.0 International license . Title: Efficacy of Nitazoxanide in reducing the viral load in COVID-19 patients. Randomized, placebo-controlled, single-blinded, parallel-group, pilot study. Authors: Marcelo Silva1, Andrés Espejo1, María L Pereyra1, Martín Lynch1, Marcos Thompson1, Hernán Taconelli2, Patricia Baré3, Matías J Pereson3, Marcelo Garbini4, Pablo Crucci4, Diego Enriquez4. Affiliations: 1Unidad de Hepatología y Trasplante Hepático, Hospital Universitario Austral, Pilar, Argentina. 2Sanatorio Nuestra Señora del Pilar, Ciudadela, Argentina. 3IIHEMA, IMEX-CONICET, Academia Nacional de Medicina. 4Departamento de Investigación Clínica, Laboratorios Roemmers. Corresponding author: Prof. Marcelo Silva, MD. Director de la Unidad de Hepatología y Trasplante Hepático, Hospital Universitario Austral, Pilar, Argentina Av. J. D. Perón 1500 (1629). Derqui, Provincia de Buenos Aires, Argentina. e-mail: msilva@cas.austral.edu.ar Abstract: The fast spread of COVID-19 has overcrowded Public Health Systems facilities in major countries due to the large number of seriously ill patients, particularly those requiring admission to intensive care units. Reducing viral load, along with other recommended epidemiological measures, such as social distancing and home confinement, can in time significantly help to reduce the infection R0 (Basic Reproductive Rate) and then mitigate disease burden. Early negativization or otherwise reduction of the viral load can potentially diminish disease severity, resulting in a better-controlled public health response, avoiding collapse of healthcare systems. Nitazoxanide, a widely used thiazolide approved by the FDA as an antiparasitic drug, also approved in Brazil for Norovirus and Rotavirus treatments, has an excellent safety record for a variety of indications. Nitazoxanide exhibits activity in vitro against MERS-CoV and other coronaviruses; and a specific antiviral effect (in micro molar doses) against SARS-CoV-2. The objective of this study was to evaluate the efficacy and safety of Nitazoxanide in reducing the SARS-COV 2 viral load within 7 days of treatment in respiratory samples from COVID-19-infected patients with mild to moderate disease, compared to placebo. An interim analysis showed that the ratio of patients with a viral load reduction ≥ 35% from baseline up to day 7 of treatment was significantly greater for Nitazoxanide compared to placebo (47.8% vs. 15.4%; Δ 34.6%; 95% CI: 64.7; 4.6: p = 0.037). 1 NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice. medRxiv preprint doi: https://doi.org/10.1101/2021.03.03.21252509; this version posted March 5, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-ND 4.0 International license . Key words: Nitazoxanide, COVID-19, viral load, antiviral, SARS-Cov-2. KEY POINTS State of the Art:  Different studies conclude that viral load (VL) would correlate with morbidity, mortality and contagiousness of..