U. S. hospitals increasingly are facing shortages of medicines used to treat serious illnesses such as cancer and heart disease, and cheaper drugs that generate lower profits for manufacturers are particularly scarce, the Associated Press reports.

“It’s just a matter of time now before we call for a drug that we need to save a patient’s life and we find out there isn’t any,” said Dr. Eric Lavonas of the American College of Emergency Physicians.

Last year there were 211 medications in short supply, triple the number five years ago. Although some of those shortages have been resolved, another 89 drugs were added to the list during the first three months of this year, according to the University of Utah’s Drug Information Service.

Most of the shortages involve injectable medications used in emergency rooms, intensive care units and cancer wards. The supply problems can last weeks or even months, and there aren’t always good substitutes.  Other countries are reporting similar problems.

The shortages are creating stress for patients and families, who fear the scarcities might be life-threatening.

At Miami Children’s Hospital, 14-year-old Caroline Pallidine had to wait a month for her last round of chemotherapy because of a prolonged shortage of cytarabine, a vital drug in the treatment of her leukemia.

“There’s always a fear, if she’s going so long without chemo, is there a chance this cancer’s going to come back?” said her mother, Marta Pallidine.

A number of factors are to blame, including contaminated vials, problems importing raw ingredients, high demand or factories that temporarily shut down to work on quality-control issues.

More expensive brand-name drugs are normally plentiful. But the Food and Drug Administration says that cheaper generic drugs often are harder to find, because of the limited numbers of manufacturers producing them.

The shortages cover a broad spectrum, including drugs used for bone marrow transplants, cystic fibrosis, cardiac arrest and even a sedative used for inmate executions.

While the number of patients harmed has not been tracked, the nonprofit Institute for Safe Medication Practices said it received two reports of patients who died after receiving the wrong dose of a morphine substitute.

To address the problem, the FDA is asking some foreign drug makers to temporarily send to the U.S. versions of scarce drugs that aren’t normally sold here. That measure boosted supplies of propofol, an important anesthetic, and the transplant drug thiotepa.

Drug companies say they are trying to catch up with demand. Hospira Inc., the largest maker of the hard-to-find injectable drugs, says it is increasing production capacity and is working with FDA to address shortages.

But the Generic Pharmaceutical Assn. says manufacturers are not always to blame, citing issues such as FDA inspections and stockpiling.

Congress is considering solutions. Sen. Herb Kohl, D-Wis., wants the Federal Trade Commission to weigh the potential impact of drug company mergers on shortages.

Legislation also is pending to require manufacturers to notify FDA in advance of problems that might trigger a shortage. The FDA prevented 38 potential shortages last year by accelerating approval of manufacturing changes or urging competing companies to ramp up production to meet demand.