More than 2,400 hospitals and related facilities have received their first doses of new drugs that are designed to keep mild to moderately ill COVID-19 patients out of the hospital. But it's not clear how much the drugs will help these patients – and whether the medicines will reduce the demand for hospital beds.

The Food and Drug Administration has granted emergency authorization to two monoclonal antibody formulations – bamlanivimab, produced by Eli Lilly, and a two-antibody combination developed by Regeneron.

These drugs are supposed to prevent the coronavirus from invading cells. Instead of being a pill or a shot, these drugs are in the form of a liquid that must be infused intravenously — a process that takes two hours or more.

"Like everything in today's world during the pandemic, our biggest challenges are around staffing," says Dr. Peter Newcomer, chief clinical officer at University of Wisconsin Health in Madison.

He said his hospital is giving the drug after-hours in an infusion center, so infectious COVID-19 patients don't cross paths with cancer patients and other vulnerable people. A special plea went out for nurses to take on yet another shift, even as the hospital struggles with rising COVID-19 cases.

The hospital can initially handle eight patients a night. Newcomer says they started with three patients Tuesday evening.

"Our advertising to the community went out Monday and Tuesday so we're going to see more tonight, and fill up all those slots real soon," he predicts.

His hospital, together with a second hospital in Madison, got an initial allocation of 112 doses. If everyone who qualifies for this treatment asks for it – including people over 65 and those with underlying conditions such as obesity, kidney disease and immunodeficiency — the hospital will quickly run out of drugs. So, UW Health set up a system to identify people who would most likely benefit. Officials will randomly pick from that pool of applicants if there isn't enough medicine to go around.

"It's basically a lottery-type system with an allocation that is done as equitably as we can," Newcomer says. The hospital developed this strategy earlier in the year to cope with a shortage of another COVID-19 drug, remdesivir. But the shortages could be far more acute with the monoclonal antibodies since so many more people are potentially eligible for them.

Informed consent for this treatment includes telling patients that it's not clear just how well these drugs actually work. The National Institutes of Health put out treatment guidelines Nov. 18 saying there's simply not enough information to know if the Lilly drug is effective. The guidelines haven't been updated to address Regeneron's drug. Emergency use authorization doesn't assure that a new product is effective, but that its potential benefits are likely to outweigh the risks.

Company studies suggest that doctors have to treat 10 to 20 patients to avoid a single hospitalization. The federal government bought hundreds of thousands of doses of these drugs and is distributing them nationally. That means patients don't have to pay for the drugs, though they may be responsible for the cost of infusion, which can run into many hundreds of dollars, depending on how insurance companies cover the procedure.

It's not clear how well the hospital's investment in staff time will pay off.

"As long as we can continue to provide this treatment, we plan on it," Newcomer says. "It's going to have to be an ongoing evaluation of what we can do from a staffing standpoint."

Hospital administrators hope the drugs are effective enough to help keep patients out of their intensive care units and other hospital beds. That's an increasingly serious issue as the coronavirus pandemic surges in the United States.

In New Mexico, "we're currently entering crisis-level stage with bed capacity," says Dr. David Gonzales, chief medical officer of CHRISTUS St. Vincent's Hospital in Santa Fe.

The hospital is sending eligible patients to its emergency room for treatment there.

"We have a portion of or emergency room that's dedicated to COVID-positive patients," Gonzales explains, so that eases concern about how to limit the risk to other patients coming for emergency care.

CHRISTUS St. Vincent's Hospital infused its first patient Tuesday, using one of the eight initial doses of the drug allotted by the state of New Mexico. After the hour-long infusion, nurses monitor patients for one to six hours to make sure there are no serious side effects. And Gonzales says that monitoring continues once patients leave the hospital, using the hospital's telemedicine services.

The logistics of delivering these drugs varies widely. In Maryland, for instance, the state designated four geographically dispersed sites, including an urgent care center in the Washington, D.C., suburbs and a field hospital set up in the Baltimore Convention Center. The University of California, San Francisco is using an infusion center that's isolated from its usual infusion center to protect patients without COVID-19.

Once a week, the federal government allocates monoclonal antibodies to states, based on a formula that considers COVID-19 cases and hospitalizations. The Department of Health and Human Services maintains a website listing allocations of the drug. It reported having distributed 85,000 doses as of last week. States, in turn, decide how to allocate the drugs within their borders.

The big question now is how much of a clamor there will be for this new and uncertain treatment.

"I expect more of a push for people to get it," says Newcomer at UW Health. "But I also expected people to wear masks regularly as well. My expectations aren't always met."

You can contact NPR Science Correspondent Richard Harris at[email protected].

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