WASHINGTON — A growing shortage of medications for a host of illnesses — from cancer to cystic fibrosis to cardiac arrest — has hospitals scrambling for substitutes to avoid patient harm, and sometimes even delaying treatment.

WASHINGTON — A growing shortage of medications for a host of illnesses — from cancer to cystic fibrosis to cardiac arrest — has hospitals scrambling for substitutes to avoid patient harm, and sometimes even delaying treatment.

"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," says Dr. Eric Lavonas of the American College of Emergency Physicians.

The problem of scarce supplies or even completely unavailable medications isn't a new one, but it's getting markedly worse. The number listed in short supply has tripled over the past five years, to a record 211 medications last year. While some of those have been resolved, another 89 drug shortages have occurred in the first three months of this year, according to the University of Utah's Drug Information Service. It tracks shortages for the American Society of Health-System Pharmacists.

The vast majority involve injectable medications used mostly by medical centers — in emergency rooms, ICUs and cancer wards. Particular shortages can last for weeks or for many months, and there aren't always good alternatives. Nor is it just a U.S. problem, as other countries report some of the same supply disruptions.

It's frightening for families.

At Miami Children's Hospital, doctors had to postpone for a month the last round of chemotherapy for 14-year-old Caroline Pallidine because of a months-long nationwide shortage of cytarabine, a drug considered key to curing a type of 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?" says her mother, Marta Pallidine, who says she'll be nervous until Caroline finishes her final treatments scheduled for this week.

There are lots of causes, from recalls of contaminated vials, to trouble importing raw ingredients, to spikes in demand, to factories that temporarily shut down for quality upgrades.

The shortage that's made the most headlines is a sedative used on death row. But on the health-care front, shortages are wide-ranging, including:

Thiotepa, used with bone marrow transplants. Norepinephrine injections for septic shock. A cystic fibrosis drug named acetylcysteine. Injections used in the ER for certain types of cardiac arrest.