High-dose oral famotidine might improve cardinal symptoms of COVID-19 infection, according to the findings of a small outpatient case series and a subsequent retrospective study.
After developing COVID-19 symptoms, the 10 patients in the case series began self-medicating with 60-240 mg famotidine daily over a median of 11 days. “All patients reported marked improvements of disease-related symptoms after starting famotidine,” first author Tobias Janowitz, MD, PhD, of Cold Spring Harbor Laboratory, N.Y., and associates wrote in.
Improvements began within 24-48 hours of starting on the histamine-2 receptor antagonist. By 14 days after treatment initiation, all patients reported near-normalization of both respiratory and systemic symptoms, the researchers reported.
The patients were 23-71 years old. Seven tested positive for COVID-19, two had antibodies to COVID-19, and one had a clinical diagnosis of COVID-19 without laboratory confirmation. Over a median of 11 days (range, 5-21 days), six patients self-administered 80 mg famotidine three times daily and four self-administered lower amounts – from 60 to 150 mg of famotidine daily, divided into two or three doses. Patients started on famotidine between 2 and 26 days after symptom onset.
Through phone interviews and questionnaires, the researchers ascertained changes in cough, dyspnea, fatigue, headache, anosmia, and general unwellness by using a modified four-point Eastern Cooperative Oncology Group (ECOG) performance status scale. Improvements were seen across all symptom categories, and respiratory symptoms improved faster than systemic symptoms. Apart from two cases of persistent anosmia, symptoms resolved completely within 14 days of starting famotidine.
Seven patients reported no side effects of famotidine; one reported grade 1 dizziness and infrequent perceptions of tachycardia; one reported grade 1 dizziness, dry skin, and insomnia; and one reported grade 1 gastrointestinal symptoms and temporary forgetfulness. “Other than forgetfulness, all of these side effects are listed in the prescription information for famotidine, and all side effects resolved on discontinuation of famotidine,” the investigators wrote.
While the findings are intriguing, Dr. Janowitz and associates cautioned against overinterpretation of them. Another expert agreed: “This is a preliminary study based on a hypothesized antiviral effect. It’s important to know that it doesn’t really prove it works,” said Amesh Adalja, MD, senior scholar at the Johns Hopkins University Center for Health Security, Baltimore, and a spokesperson for the Infectious Diseases Society of America, during an interview with MDedge.
These patients might have improved anyway, without self-administering famotidine, said Dr. Adalja, who was not involved in the study.
Furthermore, the mechanism by which famotidine might act on COVID-19 remains unclear. The drug “could have a viral target, for example, one of the viral proteases, or a host target, resulting, for example, in modulation of the immunological response to the virus,” Dr. Janowitz and associates wrote.
Dr. Adalja noted that many compounds show effects against COVID-19 that are not well understood. He called for randomized trials to evaluate the biological plausibility of famotidine use, and its potential efficacy.
“This is a cheap, over-the-counter drug, but no drug is without side effects,” he added. “We need to know whether it works.”
Based on the case series findings, researchers conducted another retrospective study of patients hospitalized with COVID-19 infection. Those who were incidentally taking famotidine before or at hospitalization had a significantly reduced risk of intubation or death, with a hazard ratio of 0.43 (Gastroenterology. 2020 May 22.)
The National Institutes of Health provided partial support. The investigators reported having no conflicts of interest.
SOURCE: Janowitz T et al. Gut. 2020 Jun 4. .