In a new study, RI-MUHC researchers have assessed all available outpatient therapies for COVID-19 to facilitate comparative treatment choice

In recent months, several drugs have shown promise in the treatment of COVID-19 outpatients to reduce the risk of serious complications. Although vaccines are effective in the fight against the COVID-19 pandemic, they remain inaccessible in many parts of the world and are shunned by a proportion of the population. Furthermore, breakthrough infections are possible with newer variants. It is therefore urgent to integrate effective and affordable drugs into the therapeutic arsenal to reduce the risk of hospitalization and, ultimately, save lives. Doctors now face a difficult decision: how do they choose between the different drugs that have been tested in clinical trials since the beginning of the pandemic?

To get a clearer picture of the options available, researchers at the Research Institute of the McGill University Health Centre (RI-MUHC) compiled the results of clinical trials of all ambulatory therapies to date and assessed their effectiveness and cost per hospitalization avoided. For each treatment, they determined the number of patients who would need to be treated to avoid one hospitalization and the associated cost of the drugs. Their findings are published today in Open Forum Infectious Diseases.

According to their study results, for an estimated 5 percent risk of hospitalization in the general population, the most effective drug is nirmatrelvir/ritonavir (known as Paxlovid and developed by Pfizer), with one hospitalization averted per 24 patients treated, at a cost of $12,720. The least effective is colchicine, with one hospitalization averted per 87 patients treated. The least expensive, however, is fluvoxamine, a common antidepressant, with a cost per hospitalization averted of $1,122 for 80 patients treated, and the most expensive, casirivimab/imdevimab, with a cost per hospitalization averted of $60,900 for 29 patients treated, and with the caveat that this drug is no longer effective against the Omicron variant. Remdesivir (developed by Gilead) and sotrovimab (a monoclonal antibody compound developed by GlaxoSmithKline) each cost about $52,000, with 28 and 25 patients respectively needing to be treated to avoid one admission. Finally, the study suggests that 50 patients would need to be treated with molnupiravir (developed by Merck) to avoid hospitalization, at a cost of $35,000.

“Available drugs, whether repurposed or new, differ in efficacy, toxicity, cost and complexity of administration. We felt it was important to conduct this study to facilitate comparative decision-making regarding treatment choice,” says the study’s senior author, Dr. Emily McDonald, a scientist in the Infectious Diseases and Immunity in Global Health Program at the RI-MUHC and an associate professor in the Department of Medicine at McGill University.

“Drugs that we can prescribe to prevent hospitalization and that cost less than an average COVID-19 hospitalization, estimated at $21,752, include nirmatrelvir/ritonavir, fluvoxamine, inhaled corticosteroids and colchicine,” adds lead study author Dr. Todd C. Lee, a scientist in the Infectious Diseases and Immunity in Global Health Program at the RI-MUHC and an associate professor in the Department of Medicine at McGill University. “Anti-spike monoclonal antibodies and remdesivir are much more expensive, and in addition to only being available in relatively limited quantities, they are more complex to obtain and administer. In some countries without access to these more expensive treatments, the choice is between supportive care and affordable repurposed drugs to treat COVID-19, such as fluvoxamine and inhaled corticosteroids.”

Increased benefits in at-risk populations

The researchers point out that the higher the individual risk of COVID-19 worsening, whether due to age or other factors related to the patient’s initial health status, the greater the absolute benefit of the drugs and the lower the cost.

“Essentially, at the right price or if prescribed to a high enough risk individual, most drugs on this list have the potential to be cost-saving to the system as a whole. Accurate country specific models for prediction of hospitalization risk will be essential in contextualizing and maximizing the benefits of any therapy,” write the authors of the study.

In order to track treatment progress for COVID-19 and to facilitate access to the most current data possible on treatment efficacy and costs, researchers have developed a webpage ( that will be updated monthly at least through the end of 2022.

About the study

The study “Outpatient Therapies for COVID-19: How do we choose?” was conducted by Todd C. Lee, Andrew M. Morris, Steven A. Grover, Srinivas Murthy and Emily G. McDonald.

About the RI-MUHC

The Research Institute of the McGill University Health Centre (RI-MUHC) is a world-renowned biomedical and healthcare research centre. The institute, which is affiliated with the Faculty of Medicine of McGill University, is the research arm of the McGill University Health Centre (MUHC) – an academic health centre located in Montreal, Canada, that has a mandate to focus on complex care within its community. The RI-MUHC supports over 450 researchers and around 1,200 research trainees devoted to a broad spectrum of fundamental, clinical and health outcomes research at the Glen and the Montreal General Hospital sites of the MUHC. Its research facilities offer a dynamic multidisciplinary environment that fosters collaboration and leverages discovery aimed at improving the health of individual patients across their lifespan. The RI-MUHC is supported in part by the Fonds de recherche du Québec – Santé (FRQS).