ACTIV-6: COVID-19 Study of Repurposed Medications - Arm F (Montelukast)

The purpose of this study is to evaluate the effectiveness of repurposed medications (study drug(s) in reducing symptoms of non-hospitalized participants with mild to moderate COVID-19. Participants will receive either study drug or placebo. They will self-report any new or worsening symptoms or medical events they may experience while taking study drug or placebo. This study is intended to be all remote with no in person visits, unless the study team feels it is in the best interest of a participant to see them in person. Prior and current drug arms are listed on clinicaltrials.gov and will be updated with the activation of any new drug arms. Each study arm will also have its own clinicaltrials.gov entry and will include \"Pro00107921\" in the Unique Protocol ID.