Abstract: pharmaceuticals Article Analyzing the Difference in the Length of Stay (LOS) in Moderate to Severe COVID-19 Patients Receiving Hydroxychloroquine or Favipiravir Bandar Alosaimi 1 , Huda M. Alshanbari 2 , Muath Alturaiqy 3 , Halah Z. AlRawi 1 , Saad Alamri 1 , Asma Albujaidy 4 , Aljawharah Bin Sabaan 5 , Ahmed A. Alrashed 6 , Ahmad Alamer 7,8 , Fayez Alghofaili 9 , Khaled Al-Duraymih 10 , Abdulaziz J. Alshalani 11 and Wael Alturaiki 9, * 1 2 3 4 5 6 7 8 9 Citation: Alosaimi, B.; Alshanbari, 10 H.M.; Alturaiqy, M.; AlRawi, H.Z.; Alamri, S.; Albujaidy, A.; Bin Sabaan, A.; Alrashed, A.A.; Alamer, A.; 11 * Research Center, King Fahad Medical City, Riyadh Second Health Cluster, Riyadh 11525, Saudi Arabia Department of Mathematical Sciences, College of Science, Princess Nourah bint Abdulrahman University, Riyadh 11671, Saudi Arabia Department of Internal Medicine, Alzulfi General Hospital, Riyadh Second Health Cluster, Riyadh 11525, Saudi Arabia Department of Clinical Pharmacy Service, Prince Mohammed bin Abdulaziz Hospital, Riyadh Second Health Cluster, Riyadh 11525, Saudi Arabia Pharmacy College, Almaarifa University, Riyadh 11597, Saudi Arabia Department of Pharmaceutical Services, Main Hospital, King Fahad Medical City, Riyadh Second Health Cluster, Riyadh 11525, Saudi Arabia Department of Clinical Pharmacy, Prince Sattam Bin Abdulaziz University, Alkharj 11942, Saudi Arabia Department of Pharmacy Practice and Science, College of Pharmacy, University of Arizona, Tucson, AZ 85721, USA Department of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Majmaah 11952, Saudi Arabia Main Laboratory and Blood Bank, Alzulfi General Hospital, Riyadh Second Health Cluster, Riyadh 11525, Saudi Arabia Alzulfi General Hospital, Riyadh Second Health Cluster, Riyadh 11525, Saudi Arabia Correspondence: w.alturaiki@mu.edu.sa Alghofaili, F.; et al. Analyzing the Difference in the Length of Stay (LOS) in Moderate to Severe COVID-19 Patients Receiving Hydroxychloroquine or Favipiravir. Pharmaceuticals 2022, 15, 1456. https://doi.org/10.3390/ph15121456 Academic Editor: Marco Fiore Received: 14 October 2022 Accepted: 18 November 2022 Published: 24 November 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ Abstract: Background: The coronavirus 2019 (COVID-19) disease, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus led to a global pandemic. HCQ and FPV were used early in the pandemic as a treatment modality for COVID-19. Various studies evaluated the HCQ and FPV effectiveness, based on the mortality endpoint and showed conflicting results. We hypothesize that analyzing the difference in the LOS as a significant endpoint would be of a major interest, especially for healthcare providers, to prevent a lengthy hospitalization and disease progression. Methods: This is a retrospective observational study, conducted via a medical chart review of COVD-19 patients who were admitted between April 2020 and March 2021 with a moderate to severe illness. The LOS endpoint was tested using the paired Wilcoxon signed-rank (WSR) model. Prior to using the WSR model, the balance..