The agency said Wednesday it immediately will begin importing trace elements, potassium phosphate and sodium phosphate — drugs used in total parenteral nutrition or TPN — from a Norwegian plant affiliated with Fresenius Kabi USA LLC, based in Lake Zurich, Ill.

“Hospitals can start ordering the drugs today,” said Valerie Jensen, associate director for the FDA’s drug shortage program.

That should start reversing a two-year shortage that has forced hospitals to ration the drugs that provide essential nutrients for patients who can’t eat or drink by mouth, said Jay Mirtallo, past president of the American Society for Parenteral or Enteral Nutrition, or ASPEN.

“I think it’s huge. It’s a great win for us,” said Mirtallo. “For too long, we’ve been limping along trying to feed our patients.”

Without adequate TPN drugs, tiny babies and other patients can develop severe side effects, including horrifying skin lesions and deficiencies that can demineralize their bones, leading to fractures, experts say. Some may have lasting developmental delays caused by missing nutrients.

The FDA is exercising regulatory discretion in allowing the drugs to be imported. When the agency turns to a foreign source, as it has for 14 other drugs in the past two years, officials evaluate the foreign drugs to make sure quality is adequate and does not pose undue risk to U.S. patients, officials said.

The move comes after 14 U.S. senators demanded earlier this month that the FDA act to end the shortage of infant drugs.

Beth Israel Medical Center in New York City led the research, conducted in 11 hospitals, which found that live music can be beneficial to premature babies. In the study, music therapists helped parents transform their favorite tunes into lullabies.

The researchers concluded that live music, played or sung, helped to slow infants’ heartbeats, calm their breathing, improve sucking behaviors important for feeding, aid sleep and promote states of quiet alertness. Doctors and researchers say that by reducing stress and stabilizing vital signs, music can allow infants to devote more energy to normal development.

And while the effects may be subtle, small improvements can be significant. Premature births have increased since 1990, to nearly 500,000 a year, one of every nine children born in the United States.

The study, published Monday in the journal Pediatrics, adds to growing research on music and preterm babies. Some hospitals find music as effective as, and safer than, sedating infants before procedures like heart sonograms and brain monitoring. Some neonatologists say babies receiving music therapy leave hospitals sooner, which can aid development and family bonding and save money.

The Office for Human Research Protections, which safeguards the people who participate in government-funded research, sent a letter to the University of Alabama at Birmingham last month, detailing what it said were violations of patients’ rights.

The university, which was a lead site for the study, had not detailed the risks in consent forms that were the basis of parents’ participation, the office said in the letter. Specifically, babies assigned to a high-oxygen group were more likely to go blind and babies assigned to a low-oxygen group were more likely to die than if they had not participated. Ultimately, 130 babies out of 654 in the low-oxygen group died, and 91 babies out of 509 in the high-oxygen group developed blindness.

Some of the 1,300 infants who participated in the study, which took place between 2004 and 2009, would probably have died or developed blindness even if they had not taken part. They were born at just 24 to 27 weeks gestation, a very high-risk category. But being assigned to one or the other oxygen group in the study increased their chances further, a risk that was not properly disclosed, the office said

Richard B. Marchase, vice president for research at the University of Alabama at Birmingham, said in a telephone interview that a similar group of infants born around the same time who did not participate in the study actually died at higher rates than those in the low-oxygen group. Those infants were not a control group in the study, but were roughly similar in number and in age to those in the study group; they had a 24 percent mortality rate, compared with a 20 percent mortality rate for the infants in the low-oxygen group.

He said the study kept the infants within the standard band of treatment for oxygen levels — 85 percent to 95 — and that its findings were forming the basis for a definition by the American Academy of Pediatrics about what the standard of care should be.

He said he had assured the Office for Human Research Protections that in the future, “we will to the best of our ability let the subjects or their parents know as thoroughly as possible what previous studies suggest in terms of risk.” He added, “We are going to be very sensitive to that going forward as we look at these consent forms.”

At least 120,000 more fragile babies may be at risk each year from an ongoing shortage of injectable zinc, a trace element added to intravenous nutrition solutions, government and medical officials say.

“It’s very frustrating,” said Dr. Lamia Soghier, medical director of the neonatology unit at Children’s National Medical Center in Washington, D.C. “What can we do? We’re just short. We don’t have it. We can’t borrow it.”

The crisis is the latest in the nation’s ongoing struggle with drug shortages. After federal intervention in 2012, the number of new shortages has fallen markedly, down to just 26 this year from a record high of 267 in 2011. But the number of active shortages of essential medications — including injectable trace elements, vitamins and electrolytes — is now 323, higher than it’s ever been, according to the University of Utah Drug Information Service, which tracks the problem.

UPDATE 3/28/13:  Emily Hartman from Children’s National Medical Center contacted PNN to clarify the following:  “While Dr. Soghier is quoted as saying “What can we do? We’re just short. We don’t have it. We can’t borrow it,” she is referring to when the original MMWR article on zinc shortages was written in December 2012. Children’s was able to get an emergency supply soon after that original article was released and we’re actually okay in terms of supply. We don’t want our patients and families to worry that this is still a problem at Children’s.”

An F.D.A. investigation of 84 cases, published in The Journal of Pediatrics in 2012, found a “distinct illness pattern” in 22 instances that suggested a possible link between SimplyThick and NEC. Seven deaths were cited; 14 infants required surgery.

Last September, after more adverse events were reported, the F.D.A. warned that the thickener should not be given to any infants. But the fact that SimplyThick was widely used at all in neonatal intensive care units has spawned a spate of lawsuits and raised questions about regulatory oversight of food additives for infants.

SimplyThick is made from xanthan gum, a widely-used food additive on the F.D.A.’s list of substances “generally recognized as safe.” SimplyThick is classified as a food and the F.D.A. did not assess it for safety.

John Holahan, president of SimplyThick, which is based in St. Louis, acknowledged that the company marketed the product to speech language pathologists who in turn recommended it to infants. The patent touted its effectiveness in breast milk.

However, Mr. Holahan said, “There was no need to conduct studies, as the use of thickeners overall was already well established. In addition, the safety of xanthan gum was already well established.”