Background: The COVID-19 pandemic due to SARS-CoV-2 infection can produce Acute Respiratory Distress Syndrome as a result of a pulmonary cytokine storm. Antihistamines are safe and effective treatments for reducing inflammation and cytokine release. Combinations of Histamine-1 and Histamine-2 receptor antagonists have been effective in urticaria, and might reduce the histamine-mediated pulmonary cytokine storm in COVID-19. Can a combination of Histamine-1 and Histamine-2 receptor blockers improve COVID-19 inpatient outcomes?

Methods: A physician-sponsored cohort study of cetirizine and famotidine was performed in hospitalized patients with severe to critical pulmonary symptoms. Pulmonologists led the inpatient care in a single medical center of 110 high-acuity patients that were treated with cetirizine 10 mg b.i.d. and famotidine 20 mg b.i.d. plus standard-of-care.

Results: Of all patients, including those with Do Not Resuscitate directives, receiving the dual-histamine receptor blockade for at least 48 h, the combination drug treatment resulted in a 16.4% rate of intubation, a 7.3% rate of intubation after a minimum of 48 h of treatment, a 15.5% rate of inpatient mortality, and 11.0 days duration of hospitalization. The drug combination exhibited beneficial reductions in inpatient mortality and symptom progression when compared to published reports of COVID-19 inpatients. Concomitant medications were assessed and hydroxychloroquine was correlated with worse outcomes.

Conclusions: This physician-sponsored cohort study of cetirizine and famotidine provides proof-of-concept of a safe and effective method to reduce the progression in symptom severity, presumably by minimizing the histamine-mediated cytokine storm. Further clinical studies in COVID-19 are warranted of the repurposed off-label combination of two historically-safe histamine receptor blockers.