Clinical Evidence for Improved Outcomes with Histamine Antagonists and Aspirin in 22,560 COVID-19 Patients

COVID-19 has spurred much interest in the therapeutic potential of repurposed drugs. A family of acid-reducing drugs, known as histamine H2 receptor antagonists (H2RA), competitively bind the H2R and block its stimulation by histamine; examples of such drugs are famotidine (e.g., Pepcid) and ranitidine (e.g., Zantac). A dense web of functionalities between histamine and H2RAs, on the one hand, and downstream cellular pathways, on the other hand, links disparate physiological pathways in gastrointestinal contexts (e.g., acid reduction) to the dysregulated inflammatory cascades (cytokine storm) underlying the pathophysiology of COVID-19. Is famotidine beneficial in treating COVID-19? This question remains unresolved, though not for lack of effort: over 10 studies have examined the potential therapeutic value of famotidine in COVID-19, but have found conflicting results (pro-famotidine, anti-famotidine, and neutral). Given the contradictory reports, we have undertaken the new analysis reported herein. Notably, studies published thus far rest upon substantially smaller datasets than drawn upon in the pre-sent work. We analyzed a cohort of 22,560 COVID-19 patients taking H1/H2 receptor antagonists, focusing on 1,379 severe cases requiring respiratory support. We analyzed outcomes for treatment with the H1RAs loratadine (e.g., Claritin) and cetirizine (e.g., Zyrtec), the H2RA famotidine, aspirin, and a famotidine & aspirin combination. For cases that reached the point of respiratory support, we found a significantly reduced fatality risk for famotidine treatment. We did not detect a benefit from dual-histamine receptor blockade (concurrently targeting H1 and H2 receptors). Notably, famotidine combined with aspirin did exhibit a significant synergistic survival benefit (odds ratio of 0.55). The relative risk for death decreased by 32.5%--an immense benefit, given the more than 2.6 million COVID-19-related deaths thus far. We found lower levels of serum markers for severe disease (e.g., C-reactive protein) in famotidine users, consistent with prior findings by others and with a role for famotidine in attenuating cytokine release. The large, international, multi-center retrospective study reported here, sampling over 250,000 COVID-19 cases, hopefully helps clarify the possible value of clinically-approved histamine antagonists such as famotidine. Given these findings, alongside the cost-effectiveness and mild side-effects of popular drugs like famotidine and aspirin, we suggest that further prospective clinical trials, perhaps utilizing the aspirin combination reported here, are advisable.

Real-world Evidence for Improved Outcomes with Histamine Antagonists and Aspirin in 22,560 COVID-19 Patients

COVID-19 has spurred much interest in the therapeutic potential of repurposed drugs, such as acid-reducing drugs that act as histamine H2 receptor antagonists (H2RA). These compounds, exemplified by famotidine (e.g., Pepcid) and ranitidine (e.g., Zantac), bind the H2R and block the histamine-triggered stimulation of signal transduction cascades. Histamine and H2RAs, on the one hand, and downstream physiological pathways, on the other hand, form a dense web of disparate pathways and signaling networks; these networks are ultimately tied to the dysregulated inflammatory cascades (cytokine storm) that underlies the pathophysiology of COVID-19. Is famotidine beneficial in treating COVID-19? This question remains unresolved, despite much recent effort: over 10 studies have examined the potential value of famotidine in COVID-19, but have found largely contradictory results. Given the conflicting reports, we have undertaken a new analysis reported herein, drawing upon a cohort of 22,560 COVID-19 patients. Using electronic health records, we statistically analyzed outcomes for treatment with the H1RAs loratadine (e.g., Claritin) and cetirizine (e.g., Zyrtec), the H2RA famotidine, the general-purpose anti-inflammatory aspirin, and a famotidine & aspirin combination. For severe cases (requiring respiratory support), we found a significantly reduced fatality risk for famotidine treatment. Notably, famotidine combined with aspirin exhibited a significant synergistic survival benefit (odds ratio of 0.55). The relative risk for death decreased by 32.5%—an immense benefit, given the more than 2.6 million COVID-19-related deaths thus far. The large, multi-center retrospective study reported here, sampling over 250,000 COVID-19 cases internationally, hopefully helps clarify the possible value of clinically-approved histamine antagonists such as famotidine. Given these findings, alongside the cost-effectiveness and mild side-effects of common over-the-counter drugs like famotidine and aspirin, we suggest that further prospective clinical trials, perhaps utilizing the aspirin combination reported here, are advisable.

Histamine Antagonists to Temper the Cytokine Overproduction in Gastrointestinal Cells Infected by SARS-CoV-2

The premise regarding COVID-19 disease is that it is a spectrum which begins with infection with viral SARS-CoV-2 exposure via airborne or oral virus particles. The individual response to it depends on many factors including co-morbid conditions. An important aspect of SARS-CoV-2 virus infection is the cytokine storm that develops after the infection. The immuno-chemical chaos created in this cytokine storm is to the benefit of the virus. In this meta analysis the authors explore ways to let the cytokine storm die down by looking into the role of histamine. Histamine is a metabolic product of the essential aminoacid histidine. Histamine has 4 known receptors: H1, H2, H3 and H4. The immunoglobulines IgE and IgM are indicative for a COVID-19 infection. This immune response is related to inflammation. Inflammation, in turn, runs mainly via histamine after e.g. virus inoculation. The goal of the meta-study is to gather evidence to primarily block the H4 receptor (H4R) in gastrointestinal cells to diminish the cytokine overproduction in the $\approx$ 30\% of the patients suffering from gastrointestinal problems caused by SARS-CoV-2. Our concept is as follows. If we can strike a careful balance between hampering the gastrointestinal spreading of the virus and histamine antagonists to tackle the cytokine storm, then the natural immunity can later on come on line again and attack the virus without being led astray by cytokine chaos. We will concentrate on H4R but also look at H1R and H2R related effects. The proposed substances in our systemic approach can be balanced for an effective early treatment. The nature of our work is by its method and results theoretical. In that respect we also may note the structural chemistry indol skeleton resemblance among a number of different drugs.

Embracing the Cascade part 2: clinical decision making in equine gastric disease

Equine gastric disease, previously referred to as Equine Gastric Ulcer Syndrome (EGUS), is now defined as two distinct disorders. Equine Squamous Gastric Disease (ESGD) is a condition of the equine stomach that is predominantly ulcerative. Equine Glandular Gastric Disease (EGGD) describes the disease of the glandular mucosa, typically a non-ulcerative condition of the pyloric region of the stomach. Acid suppression is the mainstay of therapy for ESGD, and oral omeprazole is the only medication authorised for the management of gastric ulcers (i.e. ESGD), where it is generally effective. Alternative (unauthorised) agents are usually only considered where there is treatment failure, and histamine antagonists, other proton pump inhibitors, or long-acting injectable formulations may be useful in those situations. Management of EGGD requires the use of unauthorised medicines, since no medicines are authorised for its treatment. Misoprostol, long-acting injectable omeprazole and a combination of omeprazole with sucralfate have all been described in its management and can be justified in different clinical scenarios, under the prescribing cascade.

Systemic mastocytosis: variable manifestations can lead to a challenging diagnostic process

Systemic mastocytosis results from proliferation and activation of an abnormal mast cell clone. It is a heterogeneous disorder with clinical manifestations ranging from skin lesions alone to aggressive multi-organ infiltration and decreased survival. Given these varied manifestations, diagnosis can be difficult. We describe the case of a woman who presented with rash and diarrhoea and had a history of anaphylactic reactions. Over a protracted period, the patient’s symptoms were investigated by a number of specialties including gastroenterology, dermatology, immunology and haematology. Morphological, immunohistochemical and molecular analysis of bone marrow samples ultimately led to a diagnosis of systemic mastocytosis. Management with leukotriene and histamine antagonists resulted in significant improvement in symptoms and quality of life. The case serves to highlight the protean manifestations of systemic mastocytosis, the tests available to diagnose it and the agents available to treat it.

Expression of Histidine Decarboxylase and Its Roles in Inflammation

Histamine is a well-known mediator of inflammation that is released from mast cells and basophils. To date, many studies using histamine receptor antagonists have shown that histamine acts through four types of receptors: H1, H2, H3, and H4. Thus, histamine plays more roles in various diseases than had been predicted. However, our knowledge about histamine-producing cells and the molecular mechanisms underlying histamine production at inflammatory sites is still incomplete. The histamine producing enzyme, histidine decarboxylase (HDC), is commonly induced at inflammatory sites during the late and chronic phases of both allergic and non-allergic inflammation. Thus, histamine levels in tissues are maintained at effective concentrations for hours, enabling the regulation of various functions through the production of cytokines/chemokines/growth factors. Understanding the regulation of histamine production will allow the development of a new strategy of using histamine antagonists to treat inflammatory diseases.