Anti-histamines and Covid-19: Hype or Hope

Histamine is a biogenic amine distributed extensively in the human cells. Histamine is linked with different inflammatory and allergic disorders through promoting of chemoatractant activity and endothelial changes. Antihistamine drugs are effective in the treatment and prevention of infection of influenza H7N9 through inhibition of viral entry to the host cells. A multiplicity of search strategies including experimental, preclinical and clinical studies were taken on and assumed to review the potential role of H1, H2 or their combination in the management of Coronavirus disease 2019 (Covid-19). Histamine release is associated with early and late pathology of Covid-19 and clinical presentation. Despite the potential effect of famotidine in attenuating the pathogenesis of Covid-19, famotidine has no direct effect on the replication of SARS-CoV-2. However, azelastine (H1receptor blocker) used for allergic rhinitis as nasal spray has potential anti-SARS-CoV-2 activity comparable to that of remdesivir, lopinavir and chloroquine. Azelastine is more effective than other agents that are used in the management of Covid-19 due to significant inhibition of endosomal acidification at respiratory epithelial cells. However, famotidine and cetirizine combination improve clinical outcome and reduce intubation and duration of hospitalization in Covid-19 patients. Taken together, hospitalised Covid-19 patients treated with famotidine only showed more complications as compared with those treated with combination of famotidine and cetirizine.

Both H1 and H2 blockade are effective in the management of Covid-19 patients through antiviral and anti-inflammatory properties, which together reduce the risk of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).