Therapeutic uses of Antihistamines in the Management of COVID-19: A Narrative Review

Background: The first case of COVID-19 emerged in China in 2019 and spread rapidly worldwide. Therefore, all researchers worldwide sought ways to treat and prevent the disease. Since the production of vaccines and new drugs is time-consuming, a good way is to look at existing drugs to find new effects. Objective: Due to the pathogenic mechanism of COVID-19, most of its symptoms, including anosmia, ageusia, and cytokine storm, are dependent on the release of histamine and its activities. Therefore, one category of drugs that may be effective in treating and improving the symptoms of COVID-19 is antihistamines. This paper reviewed studies that have been done so far on the effects of antihistamines, specially famotidine, in COVID-19. Methods: A literature search was performed using scientific databases such as PubMed, Web of Science, Scopus, and Google Scholar from the beginning up to December 2021. The most relevant articles considering the potential impacts of antihistamines against COVID-19 were collected. Results: In addition to the current medications prescribed for the treatment of SARS-CoV-2, H1 and H2 blockers are promising drugs for repurposing in the COVID-19 remedy. Several studies on famotidine were performed using virtual screening to determine whether they are effective. Many studies have shown that famotidine use improved COVID-19 symptoms and reduced the need for intubation and mortality. However, few studies concluded that famotidine is ineffective. Conclusion: Antihistamines, and specifically famotidine, are effective in reducing COVID-19 symptoms. Therefore, they are a good choice for combination therapy with other drugs to treat COVID-19.