Fearing the experimental use of hydroxychloroquine went “unchecked” in nursing homes struck by the coronavirus, three U.S. senators are calling on federal authorities to determine whether providers improperly treated patients, failed to disclose serious side effects or faced any repercussions from regulators responsible for oversight of the industry.

In a letter sent Thursday to the inspector general of the Department of Health and Human Services, Sens. Elizabeth Warren (D-Mass), Robert P. Casey Jr. (D-Pa.) and Ron Wyden (D-Ore.) pointed to state inspection reports that cited nursing homes for treating residents with the antimalarial drug without the consent of patients or their family members.

They also cited media accounts that chronicled the use of hydroxychloroquine in nursing homes across the country, including the 238-bed Southeastern Veterans’ Center outside Philadelphia, where doctors administered a so-called “covid cocktail” to about 30 residents in April. The drug was given to 11 residents who had not been tested for the virus, as well as those who suffered from heart ailments and other underlying conditions, The Washington Post reported.

“With regular inspections suspended and visitation by families and ombudsman limited, it is possible that other instances like these have gone unchecked,” the lawmakers said in their letter to HHS.

Among other things, they want the inspector general to investigate the level of oversight from the Centers for Medicare and Medicaid Services, the federal agency that regulates 15,000 Medicare-certified nursing homes in the United States. The senators sent letters to CMS Administrator Seema Verma and Food and Drug Administration Commissioner Stephen Hahn as well, seeking detailed information about the use of hydroxychloroquine in nursing homes.

“I am demanding answers from FDA and CMS officials about what they are doing to track the use of hydroxychloroquine and how they will ensure that residents’ rights are protected,” Casey said in a statement to The Post. “I am also asking the Inspector General to open an independent investigation. Nursing home residents need us to be their voices right now.”

A spokesperson for the FDA declined to comment, saying the agency would respond directly to the senators. CMS did not immediately provide comment Thursday.

President Trump started talking about the off-label use of anti-malarial drugs in March. The FDA subsequently issued an emergency-use authorization, but made clear the drugs should be administered only during clinical trials or in hospitals, where teams of doctors could provide intense heart monitoring. In June, the FDA announced the drugs had caused cardiac problems and other serious side effects in covid-19 patients and revoked the emergency-use authorization.

In one of the letters sent Thursday, the lawmakers asked whether the FDA has received any complaints about the use of the drug in nursing homes or tracked adverse effects among seniors.

“The Trump Administration owes us answers on the use of an ineffective drug like hydroxychloroquine in nursing homes — the epicenter of the pandemic,” Warren said in a statement.

The lawmakers referenced a nursing home in Texas that dispensed the drug without consent from patients or their family members and a home in Pennsylvania, Brighton Rehabilitation and Wellness Center, cited by state inspectors in June for giving about 200 of its 435 residents hydroxychloroquine without approval from state health authorities.

“Not only was this treatment undertaken without consultation with the state, it was still taking place five days after the FDA issued warnings against its use in non-hospital settings,” the lawmakers wrote.

Previously, Pennsylvania officials told The Post that medical providers at nursing homes did not need permission to administer hydroxychloroquine.

“Each nursing home has their own staff of doctors and medical professionals who use their clinical judgment to determine what the best form of treatment is for those who are dealing with any disease, including covid-19,” Pennsylvania Department of Health spokesperson Nate Wardle wrote in an email in June.

A state inspection that month at the Medicare-certified Southeastern Veterans’ Center made no mention of hydroxychloroquine use but cited the home for failing to manage sick patients, conduct contact tracing or protect residents from “cross-contamination, infection, virus[es] and disease.”

State Sen. Katie Muth (D), who has been investigating the facility, questioned why the use of hydroxychloroquine was flagged by the state at one nursing home and not another.

“It’s incredibly troubling,” she said. “They all should be under an effective level of regulation.”

In their letter to CMS, the senators asked whether the agency had provided any guidance to nursing homes on use of the drug — and how much Medicare may have paid for the treatment. They urged CMS to launch its own investigation.

“Nursing homes are on the front lines of the pandemic, and some of them have been following Trump’s misguided advice and giving their residents a discredited and potentially dangerous drug,” Wyden said in a statement.