- already enrolled in another covid-19 drug study - chronically taking a h1-receptor antagonist or h2-receptor antagonist - have taken h1-receptor antagonist or h2-receptor antagonist less than 72 hours from expressed interest in the study. - history of an adverse reaction to h1 or h2-receptor antagonists - severe liver disease - severe renal disease - taking steroids - taking hydroxychloroquine and/or azithromycin - already participating in a covid-19 vaccine trial - already received a covid-19 vaccine - symptoms greater than 7 days - have had covid-19 more than once

- already enrolled in another covid-19 drug study - chronically taking a h1-receptor antagonist or h2-receptor antagonist - have taken h1-receptor antagonist or h2-receptor antagonist less than 72 hours from expressed interest in the study. - history of an adverse reaction to h1 or h2-receptor antagonists - severe liver disease - severe renal disease - taking steroids - taking hydroxychloroquine and/or azithromycin - already participating in a covid-19 vaccine trial - already received a covid-19 vaccine - symptoms greater than 7 days - have had covid-19 more than once