In a striking reflection of concern over the approval of the controversial new Alzheimer’s drug Aduhelm, two major American health systems have decided that they will not administer it to patients.

The Cleveland Clinic, one of the largest and most respected medical centers in the country, said in a statement that a panel of its experts had “reviewed all available scientific evidence on this medication,” which is also called aducanumab.

“Based on the current data regarding its safety and efficacy, we have decided not to carry aducanumab at this time,” the statement said.

A spokeswoman for the clinic said that individual physicians there could prescribe Aduhelm to patients, but those patients would have to go elsewhere to receive the drug, which is administered as a monthly intravenous infusion.

Mount Sinai’s Health System in New York City has also decided not to administer Aduhelm, said Dr. Sam Gandy, director of the Mount Sinai Center for Cognitive Health.

Dr. Gandy, who is also a professor of psychiatry and neurology, said the decision was driven by the fact that there have been calls for a federal investigation to look into the F.D.A. decision and the agency’s relationship with Biogen, the drug’s manufacturer. He said, “Aduhelm will not be considered for infusion into patients on any of its campuses until and unless” an investigation by the inspector general of the Department of Health and Human Services, “affirms the integrity of the F.D.A.-Biogen relationship and goes on to reaffirm” the F.D.A.’s basis for approving the drug.

In a statement emailed in response to the developments, Biogen said, “Biogen continues to stand 100% behind Aduhelm and the clinical data that supported approval. If any patient is denied access to care, we encourage them to contact us for help as we remain committed to supporting access to Aduhelm for all appropriate patients.”

The rejection by the major medical centers is the latest fallout from the Food and Drug Administration’s approval of the drug on June 7, a decision that has also spurred congressional investigations.

Many Alzheimer’s experts and other scientists have said that it is unclear that the drug works to help slow cognitive decline and that in the best-case scenario, the evidence suggested only a slight slowing while also showing that Aduhelm could cause brain swelling or brain bleeding.

Dr. Gandy said in his private practice he tells patients that “no one was improved by Aduhelm and patients’ cognition always continued to decline at some rate.”

The drug is also expensive. Biogen, the maker, has set its price at $ 56,000 a year.

In a recent survey of nearly 200 neurologists and primary care doctors, most said they disagreed with the F.D.A. decision and did not plan to prescribe the drug to their patients.

Last week, in response to growing criticism, Dr. Janet Woodcock, the acting F.D.A. commissioner, called for an independent federal investigation into the agency’s approval process, writing that “to the extent these concerns could undermine the public’s confidence in F.D.A.’s decision, I believe it is critical that the events at issue be reviewed by an independent body.”

Two nearly identical clinical trials of Aduhelm were stopped early because an independent data monitoring committee concluded that the drug didn’t appear to be helping patients. A later analysis by Biogen found that participants receiving the high dose of the drug in one trial had experienced a very slight slowing of cognitive decline — 0.39 on an 18-point scale — but that participants in the other trial had not benefited at all.

About 40 percent of trial participants developed brain bleeding or brain swelling, and while most of those cases were mild or manageable, about 6 percent of participants dropped out of the trials because of serious adverse effects from those conditions. Dr. Gandy said that one patient in his private practice had to drop out because the patient suffered 10 brain microhemorrhages.

After evaluating the data late last year, an F.D.A. advisory committee of outside experts strongly recommended against approval, and three of its members resigned in protest last month when the agency bucked the advisory committee’s advice. The American Geriatrics Society had also urged the agency not to approve the drug, saying it would be “premature given the lack of sufficient evidence.”

Last week, in response to widespread criticism that it had approved Aduhelm for anyone with Alzheimer’s, the F.D.A. sharply narrowed the drug’s recommended use, saying it should be used only for people with mild memory or thinking problems because there was no data on Aduhelm’s use in later stages of Alzheimer’s.