Abstract: medRxiv preprint doi: https://doi.org/10.1101/2020.07.17.20155960; this version posted July 21, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.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-NC 4.0 International license . Observational Study of the Efficiency of Treatments in Patients Hospitalized with Covid-19 in Madrid Nikolas Bernaola1,​ †,*​, Raquel Mena2,​ †​, Ander Bernaola3​ ​, Cesar Carballo4​ ​, Antonio Lara5​ ​, Concha Bielza1​ ​, Pedro Larrañaga1​ Universidad Politécnica de Madrid, Spain.2​ ​ Universidad Complutense de Madrid, Spain 3​ ​ Universidad Francisco de Vitoria, Madrid, Spain ​ Hospital Universitario Ramon y Cajal, Madrid, Spain 5​ ​ Hospital Universitario Sanitas La Zarzuela, Madrid, Spain *​ Corresponding author: ​nikolasbernaola@gmail.com 1​ 4 †​ These authors contributed equally to this work. Abstract Background Many different treatments were heavily administered to patients with COVID-19 during the peak of the pandemic in Madrid without robust evidence supporting them. Methods We examined the association between sixteen treatments in four groups (steroids, antivirals, antibiotics and immunomodulators) and intubation or death. Data were obtained from patients that were admitted to an HM hospital with suspicion of COVID-19 until 24/04/2020, excluding unconfirmed diagnosis, those who were admitted before the epidemic started in Madrid, had an outcome that was not discharge or death or died within 24 hours of presentation. We compared outcomes between treated and untreated patients using propensity-score caliper matching. Results Of 2,307 patients in the dataset, 679 were excluded. Of the remaining 1,645 patients, 263 (16%) died and 311 (18.9%) died or were intubated. Except for hydroxychloroquine and prednisone, patients that were treated with any of the medications were more likely to go through an outcome of death or intubation at baseline. After propensity matching we found an association between treatment with hydroxychloroquine and prednisone and better outcomes (hazard ratios with 95% CI of 0.83 ​± ​0.06 and 0.85 ​± ​0.03). Results were similar in multiple sensitivity analyses. Conclusions In this multicenter study of patients admitted with COVID-19 hydroxychloroquine and prednisone administration was found to be associated with improved outcomes. Other treatments were associated with no effect or worse outcomes. Randomized, controlled trials of these medications in patients with COVID-19 are needed to avoid heavy administration of treatments with no strong evidence to support them. 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/10.1101/2020.07.17.20155960; this version posted July 21, 2020. 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-NC 4.0 International license .