Objective: There is an urgent need for effective treatments to prevent or attenuate lung and systemic inflammation, endotheliitis, and thrombosis related to COVID-19. This study aimed to assess the effectiveness of a multidrug-therapy consisting of Ivermectin, Azithromycin, Montelukast, and Acetylsalicylic acid ("TNR4" therapy) to prevent hospitalization and death among ambulatory COVID19 cases in Tlaxcala, Mexico. Design and methods: A comparative effectiveness study was performed among 768 confirmed SARS-CoV2 cases aged 18–80 years, who received ambulatory care at the Ministry of Health of Tlaxcala. A total of 481 cases received the TNR4 therapy, while 287 received another treatment (comparison group). All...