Dexchlorpheniramine for COVID-19

With the rollout of multiple COVID-19 vaccines, adjunctive treatments for COVID-19 have received less attention. Breakthrough infections post-vaccination (including boosters) underscore the need to continue evaluating repurposed drugs and nutraceuticals as candidate adjunctive treatments. Early clinical studies of antihistamines hypothesized that targeting mast cells (and/or histamine receptors) might benefit COVID-19 patients. In cultured human coronary artery endothelial cells, histamine potentiated spike-mediated angiotensin-converting enzyme 2 internalization; this effect can be blocked by the antihistamine famotidine. This literature review focuses on clinical studies of antihistamines, mast cell stabilizers, and leukotriene receptor antagonists for COVID-19 patients. Several antihistamines and mast cell-targeting agents, including fluvoxamine, cyproheptadine, hydroxyzine, and antihistamines used alone or with azithromycin (dexchlorpheniramine, cetirizine, loratadine, and ebastine), as well as azelastine, famotidine (standard or high-dose), high-dose famotidine with celecoxib, and the flavonoid mast cell stabilizer quercetin, have been reported to be associated with clinical benefits in COVID-19 patients. Multiple studies have reported mixed results for aspirin, montelukast, and normal-dose famotidine; patients taking aspirin often have associated COVID-19 risk factors. In the context of current standard-of-care treatments, clinical studies evaluating candidate adjunctive treatments should carefully consider and avoid known drug–drug interactions, such as those involving celecoxib and dexamethasone. Further clinical studies of the identified treatments targeting mast cells and/or histamine receptors in COVID-19 patients associated with clinical benefits are therefore strongly recommended.

Background and Objectives This study was aimed to determine the effect of antihistamines on Covid-19 disease. Subjects and Methods Two researchers searched online electronic databases PubMed, MEDLINE and Google Scholar from the beginning of the pandemic until December 30, 2022 using Mesh and keywords such as: "SARS-CoV-2" or "COVID-19" and "Antihistamine". Results The results depicted that levocetirizine, diphenhydramine, hydroxyzine, azelastine, dexchlorpheniramine, cetirizine, loratadine, desloratadine, fexofenadine, triprolidine, dimetindene, and famotidine are effective in treating and reducing the symptoms of Covid-19. Among them, famotidine had contradictory results, and although it may be a useful supplement in the treatment of covid-19, laboratory studies have failed to show the direct role of famotidine in controlling this disease. Conclusion From the above-discussed findings regarding antihistamines and Covid-19, specific antihistamines should be identified and included as an essential therapeutic approach for the management of Covid-19 alongside other approaches. In fact, antihistamines appear to be promising in the management of Covid-19 with a short time to relieve symptoms while giving the body enough time to reset its defense mechanism, thus reaching a rapid recovery. They work by both modulating histamine pathways and suppressing virus growth. Despite the fact that more trials and clinical studies still need to be done on the identification and deployment of potential antihistamines in the management of Covid-19, there is not enough time for this given the enormous threat of this global health crisis. Selective antihistamines, particularly histamine H1 receptor antagonists, should now be approved for emergency use for the management of Covid-19.