Histamine-2 Receptor Antagonists and Proton Pump Inhibitors Are Associated With Reduced Risk of SARS-CoV-2 Infection Without Comorbidities Including Diabetes, Hypertension, and Dyslipidemia: A Propensity Score-Matched Nationwide Cohort Study.

BACKGROUND: This study aimed to identify the effect of histamine-2 receptor antagonist (H2RA) and proton pump inhibitor (PPI) use on the positivity rate and clinical outcomes of coronavirus disease 2019 (COVID-19). METHODS: We performed a nationwide cohort study with propensity score matching using medical claims data and general health examination results from the Korean National Health Insurance Service. Individuals aged ≥ 20 years who were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) between 1 January and 4 June 2020 were included. Patients who were prescribed H2RA or PPI within 1 year of the test date were defined as H2RA and PPI users, respectively. The primary outcome was SARS-CoV-2 test positivity, and the secondary outcome was the instance of severe clinical outcomes of COVID-19, including death, intensive care unit admission, and mechanical ventilation administration. RESULTS: Among 59,094 patients tested for SARS-CoV-2, 21,711 were H2RA users, 12,426 were PPI users, and 24,957 were non-users. After propensity score matching, risk of SARS-CoV-2 infection was significantly lower in H2RA users (odds ratio [OR], 0.85; 95% confidence interval [CI], 0.74-0.98) and PPI users (OR, 0.62; 95% CI, 0.52-0.74) compared to non-users. In patients with comorbidities including diabetes, dyslipidemia, and hypertension, the effect of H2RA and PPI against SARS-CoV-2 infection was not significant, whereas the protective effect was maintained in patients without such comorbidities. Risk of severe clinical outcomes in COVID-19 patients showed no difference between users and non-users after propensity score matching either in H2RA users (OR, 0.89; 95% CI, 0.52-1.54) or PPI users (OR, 1.22; 95% CI, 0.60-2.51). CONCLUSION: H2RA and PPI use is associated with a decreased risk for SARS-CoV-2 infection but does not affect clinical outcome. Comorbidities including diabetes, hypertension, and dyslipidemia seem to offset the protective effect of H2RA and PPI.

Famotidine activates the vagus nerve inflammatory reflex to attenuate cytokine storm.

BACKGROUND: Severe COVID-19 is characterized by pro-inflammatory cytokine release syndrome (cytokine storm) which causes high morbidity and mortality. Recent observational and clinical studies suggest famotidine, a histamine 2 receptor (H2R) antagonist widely used to treat gastroesophageal reflux disease, attenuates the clinical course of COVID-19. Because evidence is lacking for a direct antiviral activity of famotidine, a proposed mechanism of action is blocking the effects of histamine released by mast cells. Here we hypothesized that famotidine activates the inflammatory reflex, a brain-integrated vagus nerve mechanism which inhibits inflammation via alpha 7 nicotinic acetylcholine receptor (α7nAChR) signal transduction, to prevent cytokine storm. METHODS: The potential anti-inflammatory effects of famotidine and other H2R antagonists were assessed in mice exposed to lipopolysaccharide (LPS)-induced cytokine storm. As the inflammatory reflex is integrated and can be stimulated in the brain, and H2R antagonists penetrate the blood brain barrier poorly, famotidine was administered by intracerebroventricular (ICV) or intraperitoneal (IP) routes. RESULTS: Famotidine administered IP significantly reduced serum and splenic LPS-stimulated tumor necrosis factor (TNF) and IL-6 concentrations, significantly improving survival. The effects of ICV famotidine were significantly more potent as compared to the peripheral route. Mice lacking mast cells by genetic deletion also responded to famotidine, indicating the anti-inflammatory effects are not mast cell-dependent. Either bilateral sub-diaphragmatic vagotomy or genetic knock-out of α7nAChR abolished the anti-inflammatory effects of famotidine, indicating the inflammatory reflex as famotidine's mechanism of action. While the structurally similar H2R antagonist tiotidine displayed equivalent anti-inflammatory activity, the H2R antagonists cimetidine or ranitidine were ineffective even at very high dosages. CONCLUSIONS: These observations reveal a previously unidentified vagus nerve-dependent anti-inflammatory effect of famotidine in the setting of cytokine storm which is not replicated by high dosages of other H2R antagonists in clinical use. Because famotidine is more potent when administered intrathecally, these findings are also consistent with a primarily central nervous system mechanism of action.

Comparative risk of incidence and clinical outcomes of COVID-19 among proton pump inhibitor and histamine-2 receptor antagonist short-term users: a nationwide retrospective cohort study.

BACKGROUND: This study aimed to evaluate incidence risk and adverse clinical outcomes in COVID-19 disease among short-term users of acid-suppressants in South Korea. METHODS: This retrospective cohort study, conducted using a nationwide claims database for South Korea, used data from patients with COVID-19 tested between January 1 and May 15, 2020. Patients aged over 18 years and prescribed proton pump inhibitors (PPI) or histamine-2 receptor antagonist (H2RA) for more than 7 days were identified. Primary outcome was COVID-19 while secondary outcomes were all-cause mortality, hospitalization with respiratory disease, or intensive respiratory intervention. Large-scale propensity scores were used to match patients, while the Cox proportional hazard model was utilized to evaluate any association between exposure and outcome(s). The risk estimates were calibrated by using 123 negative control outcomes. RESULTS: We identified 26,166 PPI users and 62,117 H2RA users. After propensity score matching, compared to H2RA use, PPI use was not significantly associated with lower risk of COVID-19 (calibrated hazard ratio [HR], 0.81 [95% confidence interval (CI), 0.30-2.19]); moreover, PPI use was not associated with adverse clinical outcomes in COVID-19, namely, hospitalization with respiratory disease (calibrated HR, 0.88 [95% CI, 0.72-1.08]), intensive respiratory interventions (calibrated HR, 0.92 [95% CI, 0.46-1.82]), except for all-cause mortality (calibrated HR, 0.54 [95% CI, 0.31-0.95]). CONCLUSIONS: In this study, we found that the PPI user was not associated with risk of COVID-19 compared to H2RA users. There was no significant relationship between severe clinical outcomes of COVID-19 and exposure to PPI compared with H2RA, except for all-cause mortality.

Acid suppressant use in association with incidence and severe outcomes of COVID-19: a systematic review and meta-analysis.

PURPOSE: Several observational studies have presented conflicting results on the association between the use of proton pump inhibitors (PPIs) or histamine H2 receptor antagonist (H2RA) and the risk of coronavirus disease 2019 (COVID-19). This systematic review and meta-analysis aimed to examine this association. METHODS: In July 2021, PubMed, Embase, Cochrane Central Register of Controlled Trials, and Web of Science were searched for articles investigating the relationship between the two main acid suppressants and COVID-19. Studies showing the effect estimates as hazard ratio (HR) for severe outcomes or incidence of COVID-19 were evaluated using a random-effects model. RESULTS: A total of 15 retrospective cohort studies with 18,109 COVID-19 cases were included in the current meta-analysis. PPI use was significantly associated with severe outcomes of COVID-19 (hazard ratio [HR] = 1.53; 95% confidence interval [CI]: 1.20-1.95) but not with the incidence of COVID-19, whereas H2RA use was significantly associated with decreased incidence (HR = 0.86, 95% CI: 0.76-0.97). For subgroup analyses of PPIs, increased severe outcomes of COVID-19 were observed in < 60 years, active use, in-hospital use, and Asians. For subgroup analyses of H2RAs, decreased severe outcomes of COVID-19 were observed in > 60 years, while in-hospital use and use in Asia were associated with higher disease severity. CONCLUSIONS: Close observation can be considered for COVID-19 patients who use PPIs to prevent severe outcomes. However, caution should be taken because of substantial heterogeneity and plausible protopathic bias.

Effect of famotidine on hospitalized patients with COVID-19: A systematic review and meta-analysis.

INTRODUCTION: Famotidine is a competitive histamine H2-receptor antagonist most commonly used for gastric acid suppression but thought to have potential efficacy in treating patients with Coronavirus disease 2019 (COVID-19). The aims of this systematic review and meta-analysis are to summarize the current literature and report clinical outcomes on the use of famotidine for treatment of hospitalized patients with COVID-19. METHODS: Five databases were searched through February 12, 2021 to identify observational studies that reported on associations of famotidine use with outcomes in COVID-19. Meta-analysis was conducted for composite primary clinical outcome (e.g. rate of death, intubation, or intensive care unit admissions) and death separately, where either aggregate odds ratio (OR) or hazard ratio (HR) was calculated. RESULTS: Four studies, reporting on 46,435 total patients and 3,110 patients treated with famotidine, were included in this meta-analysis. There was no significant association between famotidine use and composite outcomes in patients with COVID-19: HR 0.63 (95% CI: 0.35, 1.16). Across the three studies that reported mortality separated from other endpoints, there was no association between famotidine use during hospitalization and risk of death-HR 0.67 (95% CI: 0.26, 1.73) and OR 0.79 (95% CI: 0.19, 3.34). Heterogeneity ranged from 83.69% to 88.07%. CONCLUSION: Based on the existing observational studies, famotidine use is not associated with a reduced risk of mortality or combined outcome of mortality, intubation, and/or intensive care services in hospitalized individuals with COVID-19, though heterogeneity was high, and point estimates suggested a possible protective effect for the composite outcome that may not have been observed due to lack of power. Further randomized controlled trials (RCTs) may help determine the efficacy and safety of famotidine as a treatment for COVID-19 patients in various care settings of the disease.

Case-control study of the association of chronic acid suppression and social determinants of health with COVID-19 infection.

Acid suppressants are widely-used classes of medications linked to increased risks of aerodigestive infections. Prior studies of these medications as potentially reversible risk factors for COVID-19 have been conflicting. We aimed to determine the impact of chronic acid suppression use on COVID-19 infection risk while simultaneously evaluating the influence of social determinants of health to validate known and discover novel risk factors. We assessed the association of chronic acid suppression with incident COVID-19 in a 1:1 case-control study of 900 patients tested across three academic medical centers in California, USA. Medical comorbidities and history of chronic acid suppression use were manually extracted from health records by physicians following a pre-specified protocol. Socio-behavioral factors by geomapping publicly-available data to patient zip codes were incorporated. We identified no evidence to support an association between chronic acid suppression and COVID-19 (adjusted odds ratio 1.04, 95% CI 0.92-1.17, P = 0.515). However, several medical and social features were positive (Latinx ethnicity, BMI ≥ 30, dementia, public transportation use, month of the pandemic) and negative (female sex, concurrent solid tumor, alcohol use disorder) predictors of new infection. These findings demonstrate the value of integrating publicly-available databases with medical data to identify critical features of communicable diseases.

Drug therapies for reducing gastric acidity in people with cystic fibrosis.

BACKGROUND: Malabsorption of fat and protein contributes to poor nutritional status in people with cystic fibrosis. Impaired pancreatic function may also result in increased gastric acidity, leading in turn to heartburn, peptic ulcers and the impairment of oral pancreatic enzyme replacement therapy. The administration of gastric acid-reducing agents has been used as an adjunct to pancreatic enzyme therapy to improve absorption of fat and gastro-intestinal symptoms in people with cystic fibrosis. It is important to establish the evidence regarding potential benefits of drugs that reduce gastric acidity in people with cystic fibrosis. This is an update of a previously published review. OBJECTIVES: To assess the effect of drug therapies for reducing gastric acidity for: nutritional status; symptoms associated with increased gastric acidity; fat absorption; lung function; quality of life and survival; and to determine if any adverse effects are associated with their use. SEARCH METHODS: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register which comprises references identified from comprehensive electronic and non-electronic database searches, handsearches of relevant journals,  abstract books and conference proceedings. Both authors double checked the reference lists of the searches Most recent search of the Group's Trials Register: 26 April 2021. On the 26 April 2021 further searches were conducted on the clinicaltrials.gov register to identify any ongoing trials that may be of relevance. The WHO ICTRP database was last searched in 2020 and is not currently available for searching due to the Covid-19 pandemic. SELECTION CRITERIA: All randomised and quasi-randomised trials involving agents that reduce gastric acidity compared to placebo or a comparator treatment. DATA COLLECTION AND ANALYSIS: Both authors independently selected trials, assessed trial quality and extracted data. MAIN RESULTS: The searches identified 40 trials; 17 of these, with 273 participants, were suitable for inclusion, but the number of trials assessing each of the different agents was small. Seven trials were limited to children and four trials enrolled only adults. Meta-analysis was not performed, 14 trials were of a cross-over design and we did not have the appropriate information to conduct comprehensive meta-analyses. All the trials were run in single centres and duration ranged from five days to six months. The included trials were generally not reported adequately enough to allow judgements on risk of bias. However, one trial found that drug therapies that reduce gastric acidity improved gastro-intestinal symptoms such as abdominal pain; seven trials reported significant improvement in measures of fat malabsorption; and two trials reported no significant improvement in nutritional status. Only one trial reported measures of respiratory function and one trial reported an adverse effect with prostaglandin E2 analogue misoprostol. No trials have been identified assessing the effectiveness of these agents in improving quality of life, the complications of increased gastric acidity, or survival. AUTHORS' CONCLUSIONS: Trials have shown limited evidence that agents that reduce gastric acidity are associated with improvement in gastro-intestinal symptoms and fat absorption. Currently, there is insufficient evidence to indicate whether there is an improvement in nutritional status, lung function, quality of life, or survival. Furthermore, due to the unclear risks of bias in the included trials, we are unable to make firm conclusions based on the evidence reported therein. We therefore recommend that large, multicentre, randomised controlled clinical trials are undertaken to evaluate these interventions.

Famotidine Repurposing for Novel Corona Virus Disease of 2019: A Systematic Review.

BACKGROUND: COVID-19 caused by SARS-CoV-2 was declared as a global pandemic by the WHO. Famotidine is a histamine-2 (H2) receptor antagonist which blocks the H2 receptors in the parietal cells, decreasing gastric acid secretion. Our review aims to study all the available scientific evidence on famotidine research outcomes systematically to introspect its clinical efficacy and probable mechanisms and clinical efficacy against SARS-CoV-2. METHODOLOGY: An electronic search of PubMed, Scopus and Google Scholar was performed using MeSH terms "SARS CoV-2" OR "COVID-19" AND"FAMOTIDINE". Relevant informationwas extracted from studies reporting the efficacy of famotidine in COVID-19. RESULTS: We found a total of 32 studies, out of which only 14 were relevant and were included in our review.Molecular computational studies showed that famotidine selectively acts on viral replication proteases papain-like protease (PLpro) and 3-chymotrypsin-like protease (3CLpro). Additionally, it acts via inverse-agonism on the H2 receptors present in neutrophils and eosinophils which leads to inhibition of cytokine release. Clinical study findings have pointed toward significant improvements in COVID-19 patient-reported symptoms in non-hospitalized patients and reduction in intubation or death in critically ill patients associated with the usage of famotidine. However,in one of the studies,famotidine has failed to show any significant benefit in reducing mortality due to COVID-19. CONCLUSION: Famotidine has the potential to answer the ongoing global challenge owing to its selective action on viral replication. Additionally, clinical findings in COVID-19 patients support its efficacy to reduce clinical symptoms of COVID-19.We suggest that further optimally powered randomized clinical trials should be carried out to come up with definitive conclusions.

Does Famotidine Reduce the Risk of Progression to Severe Disease, Death, and Intubation for COVID-19 Patients? A Systemic Review and Meta-Analysis.

BACKGROUND: Famotidine was reported to potentially provide benefits to Coronavirus Disease 2019 (COVID-19) patients. However, it remains controversial whether it is effective in treating COVID-19. AIMS: This study aimed to explore whether famotidine use is associated with reduced risk of the severity, death, and intubation for COVID-19 patients. METHODS: This study was registered on International Prospective Register of Systematic Reviews (PROSPERO) (ID: CRD42020213536). A comprehensive search was performed to identify relevant studies up to October 2020. I-squared statistic and Q-test were utilized to assess the heterogeneity. Pooled risk ratios (RR) and 95% confidence intervals (CI) were calculated through the random effects or fixed effects model according to the heterogeneity. Subgroup analyses, sensitivity analysis, and publication bias assessment were also conducted. RESULTS: Five studies including 36,635 subjects were included. We found that famotidine use was associated with a statistically non-significant reduced risk of progression to severe disease, death, and intubation for Coronavirus Disease 2019 (COVID-19) patients (pooled RR was 0.82, 95% CI = 0.52-1.30, P = 0.40). CONCLUSION: Famotidine has no significant protective effect in reducing the risk of developing serious illness, death, and intubation for COVID-19 patients. More original studies are needed to further clarify whether it is associated with reduced risk of the severity, death, and intubation for COVID-19 patients.

Molecular basis for the repurposing of histamine H2-receptor antagonist to treat COVID-19.

With the world threatened by a second surge in the number of Coronavirus cases, there is an urgent need for the development of effective treatment for the novel coronavirus (COVID-19). Recently, global attention has turned to preliminary reports on the promising anti-COVID-19 effect of histamine H2-receptor antagonists (H2RAs), most especially Famotidine. Therefore, this study was designed to exploit a possible molecular basis for the efficacy of H2RAs against coronavirus. Molecular docking was performed between four H2RAs, Cimetidine, Famotidine, Nizatidine, Ranitidine, and three non-structural proteins viz. NSP3, NSP7/8 complex, and NSP9. Thereafter, a 100 ns molecular dynamics simulation was carried out with the most outstanding ligands to determine the stability. Thereafter, Famotidine and Cimetidine were subjected to gene target prediction analysis using HitPickV2 and eXpression2Kinases server to determine the possible network of genes associated with their anti-COVID activities. Results obtained from molecular docking showed the superiority of Famotidine and Cimetidine compared to other H2RAs with a higher binding affinity to all selected targets. Molecular dynamic simulation and MMPBSA results revealed that Famotidine as well as Cimetidine bind to non-structural proteins more efficiently with high stability over 100 ns. Results obtained suggest that Famotidine and Cimetidine could be a viable option to treat COVID-19 with a mechanism of action that involves the inhibition of viral replication through the inhibition of non-structural proteins. Therefore, Famotidineand Cimetidine qualify for further study as a potential treatment for COVID-19.

Dapsone as treatment adjunct in ARDS.

Multiple pharmacological interventions tested over the last decades have failed to reduce ARDS mortality. This short note recounts past data indicating that (i) neutrophils home along an IL-8 gradient, (ii) in ARDS, massive neutrophil accumulation and degranulation in and along bronchoalveolar spaces contributes to damage and hypoxia, (iii) large increases in IL-8 are one of the chemotaxic signals drawing neutrophils to the ARDS lung, and (iv) old data from dermatology and glioblastoma research showed that the old drug against Hansen's disease, dapsone, inhibits neutrophils' chemotaxis to IL-8. Therefore dapsone might lower neutrophils' contributions to ARDS lung pathology. Dapsone can create methemoglobinemia that although rarely problematic it would be particularly undesirable in ARDS. The common antacid drug cimetidine lowers risk of dapsone related methemoglobinemia and should be given concomitantly.