H2RAs and COVID-19
H2RA also suppresses the production of gastric acid. Cimetidine, ranitidine, famotidine and nizatidine are examples of H2RAs. Early data show that H2RAs had antiviral properties inhibiting HIV replication in vitro (21). Famotidine’s role in SARS-CoV-2 was elucidated in a study by Wu et al. (22). There is a potential role of famotidine in interfering maturation of SARS-CoV-2 and reducing inflammation. This knowledge has spurred an interest in the potential of the drug.
The results of a recent propensity score-matched retrospective cohort study involving hospitalised COVID-19 patients in New York were promising (13). This study by Freedberg et al. showed that in patients hospitalised with COVID-19 and not initially intubated, famotidine use was associated with a two-fold reduction in clinical deterioration leading to intubation or death (adjusted hazard ratio 0.42, 95% CI 0.21–0.85). However, this effect was not observed in PPI users for unclear reasons.
Similarly, a study by Janowitz et al., revealed self-administration of famotidine is associated with symptomatic improvements in a case series of 10 consecutive patients (14). The results of this case series suggest that high-dose oral famotidine is well tolerated and associated with improved patient-reported outcomes in non-hospitalised patients with COVID-19.
The findings of the above two studies are observational and should not be interpreted to mean that famotidine has a protective effect against COVID-19. Currently, clinical trials are underway to determine whether H2RAs might protect against the COVID-19 for reasons unrelated to pH balance. The results of a multicentre, randomised controlled trial (RCT) (NCT04370262) of intravenous famotidine in COVID-19 is eagerly awaited (23).