H2 antagonists should be investigated as a potential treatment for COVID-19 disease according to US clinicians who say patients experience significant improvements in symptoms such as breathlessness and fatigue when using famotidine.

The effects of famotidine in non-hospitalised patients were observed within 24 to 48 hours of taking the drug, according to a case series of 10 patient reported in Gut journal by doctors from Cold Spring Harbor Laboratory, New York.

Anecdotal reports of improvement in COVID-19 symptoms from patients self medicating with the OTC antacid led the researchers to enrol further patients in a preliminary series to investigate the severity of five cardinal symptoms–cough; shortness of breath; fatigue; headache and loss of taste/smell as well as general unwellness measured using a version of a 4-point scale normally applied to assess the severity of cancer symptoms (ECOG PS).

Seven of the 10 patients tested positive for COVID-19, using a swab test; two had antibodies to the infection; and one patient wasn’t tested but was diagnosed with the infection by a doctor.

All started taking famotidine within two to 26 days of the first COVID-19 symptoms. The most frequently used dose was 80 mg taken three times a day, with the average treatment period lasting 11 days, but ranging from five to 21 days.

All 10 patients said that symptoms quickly improved within 24-48 hours of starting famotidine and had mostly cleared up after 14 days.

Improvement was evident across all symptom categories assessed, but respiratory symptoms, such as cough and shortness of breath improved more rapidly than systemic symptoms, such as fatigue. Home monitored oxygen saturation levels improved in several patients within two days of starting famotidine

Seven of the patients didn’t experience any side effects while on famotidine, and in the three who did, these were mild, and all but temporary forgetfulness were known side effects associated with taking the drug.

While promising, the researchers acknowledge the findings may reflect a placebo effect, enrolment and recall bias and the natural course of recovery.

Mechanistically, famotidine 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, they suggest.

“Our case series suggests, but does not establish, a benefit from famotidine treatment in outpatients with COVID-19,” they caution.

Nevertheless, given the safety and wide availability of famotidine, they suggest their findings warrant further more detailed study.

“An outpatient study of oral famotidine that investigates efficacy for symptom control, viral burden and disease outcome and assesses the effects of medication use on long term immunity should be considered to establish if famotidine may be of use in controlling COVID-19 in individual patients while also reducing the risk of SARS-CoV-2 transmission,” they conclude.