Abstract: Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active. International Journal of Antimicrobial Agents 56 (2020) 106136 Contents lists available at ScienceDirect International Journal of Antimicrobial Agents journal homepage: www.elsevier.com/locate/ijantimicag Effects of Hydroxychloroquine on Covid-19 in Intensive Care Unit Patients: Preliminary Results Alexandre Lopez a,∗, Gary Duclos a, Bruno Pastene a, Karine Bezulier a, Romain Guilhaumou b, Caroline Solas c, Laurent Zieleskiewicz a,d, Marc Leone a a Aix-Marseille University, Assistance Publique Hôpitaux de Marseille, Department of Anesthesiology and Intensive Care, Hôpital Nord, Marseille, 13015, France Service de Pharmacologie Clinique et Pharmacovigilance, APHM, Institut de neurosciences des systèmes, Inserm UMR 1106, Université d’Aix-Marseille, France. c Aix-Marseille University, APHM, UMR "Emergence des Pathologies Virales" Inserm 1207 IRD 190, Laboratoire de Pharmacocinétique et Toxicologie, Hôpital La Timone, 13005 Marseille, France d Center for Cardiovascular and Nutrition Research (C2VN) Aix Marseille Université, INSERM, INRA, Marseille, 13005, France. b a r t i c l e Keywords: Hydroxychloroquine Intensive care unit Covid-19 pneumonia i n f o a b s t r a c t During the Covid-19 pandemic, many intensive care unit (ICU) patients received hydroxychloroquine. The primary objective of this study was to assess the effects of hydroxychloroquine according to its plasma concentration in ICU patients. A single-center retrospective study was performed from March to April 2020 in an ICU of a university hospital. All patients admitted to the ICU with confirmed Covid-19 pneumonia and treated with hydroxychloroquine were included. The study compared 17 patients in whom the hydroxychloroquine plasma concentration was in the therapeutic target (on-target) and 12 patients in whom the plasma concentration was below the target (off-target). The follow-up of patients was 15 days. No association was found between hydroxychloroquine plasma concentration and viral load evolution (P = 0.77). There was no significant difference between the two groups for duration of mechanical ventilation, length of ICU stay, in-hospital mortality, and 15-days mortality. These findings indicate that hydroxychloroquine administration for Covid-19 patients hospitalized in ICU is not associated with improved outcomes. Larger multicenter studies are needed to confirm these results. © 2020 Elsevier Ltd and International Society of Antimicrobial Chemotherapy. All rights reserved.