Effectiveness of famotidine on the risk of poor prognosis in patients with COVID-19: A nationwide cohort study in Korea

Objective: Famotidine has been proposed as a promising candidate for the treatment of coronavirus disease 2019 (COVID-19). However, there is limited research on the association of famotidine with the poor prognosis of COVID-19. Methods: The Korean nationwide cohort included 6,556 patients who tested positive on RT- PCR for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The poor COVID- 19-related outcomes were defined on the basis of having encountered the composite outcome of high oxygen therapy, intensive care unit admission, administration of mechanical ventilation, or death. In addition, we performed exposure-driven propensity score matching for no H2-blocker use versus current famotidine use, and other H2-blocker use versus current famotidine use. Results: 4,785 (73.0%) patients did not use a H2-blocker, 393 (6.0%) patients were currently used famotidine, and 1,292 (19.7%) patients currently used H2-blocker other than famotidine. In multivariable analysis after matching (no H2-blocker use versus current famotidine use), there was no significant association between current famotidine use and composite outcomes (adjusted odd ratios [aOR]: 1.30, 95% confidence interval [CI]: 0.55-3.06). On the other hand, another matched cohort (other H2-blocker use versus current famotidine use), demonstrated a positive association between current famotidine use and composite outcomes (aOR: 3.56, 95% CI: 1.03-12.28) Conclusions: Our study results did not support the potential of famotidine as a therapeutic agent for COVID-19. A rather unexpected result could be observed in the comparisons between current famotidine use and other H2-blocker use; it was observed that current famotidine use increased the risk of poor COVID-19 related outcomes. Further studies are needed to clearly prove the causal relationship with several H2-blockers, including famotidine.