A Silicon Valley company that charged patients for infusions of blood plasma from younger donors said Tuesday that it has stopped treating patients. The announcement followed a warning from the Food and Drug Administration that advises consumers against such treatments. The company, Ambrosia, charged patients as much as $12,ooo for treatments that were advertised to prevent aging and memory loss. The blood was donated by 16- to 25-year-olds, for consumers ages 35 and older. The FDA said there is no proof that plasma from young donors can be used as a treatment for dementia, Parkinson’s disease, multiple sclerosis, Alzheimer’s disease, or post-traumatic stress disorder, as companies offering the treatment claimed. Such firm were able to avoid the FDA drug-approval process because plasma transfusions are a well-established procedure.

The FDA also warned that the plasma infusions can be dangerous, because they are associated with infectious, allergic, respiratory, and cardiovascular risks. “We’re alerting consumers and health-care providers that treatments using plasma from young donors have not gone through the rigorous testing that the FDA normally requires in order to confirm the therapeutic benefit of a product and to ensure its safety,” said Scott Gottlieb, the FDA’s commissioner, and Peter Marks, director of the agency’s Center for Biologics Evaluation and Research, in a statement.