Paul Davis, the chief of a rural ambulance squad in southern Ohio, was down to his last vial of morphine earlier this fall when a woman with a broken leg needed a ride to the hospital.

The trip was 30 minutes, and the patient was in pain. But because of a nationwide shortage, his morphine supply had dwindled from four doses to one, presenting Davis with a stark quandary. Should he treat the woman, who was clearly suffering? Or should he save it for a patient who might need it more?

In the end, he opted not to give her the morphine, a decision that haunts him still.

“I just feel like I’m not doing my job,” said Davis, who is chief of the rescue squad in Vernon, Ohio.

He has since refilled his supply.

“I shouldn’t have to make those kinds of decisions,” Davis said.

From rural ambulance squads to prestigious hospitals, health care workers are struggling to keep vital medicines in stock because of a drug shortage crisis that is proving to be stubbornly difficult to fix. Rationing is just one example of the extraordinary lengths being taken to address the shortage, which health care workers say has ceased to be a temporary emergency and is now a fact of life. In desperation, they are resorting to treating patients with less effective alternatives and using expired drugs. The Cleveland Clinic has hired a pharmacist whose only job is to track down hard-to-find drugs.

Caused largely by an array of manufacturing problems, the shortage has prompted congressional hearings, a presidential order and pledges by generic drug makers to communicate better with federal regulators.

The problem peaked in 2011, when a record 251 drugs were declared in short supply. This year, slightly more than 100 were placed on the list, and workers say the battle to keep pharmacy shelves stocked continues unabated. The list of hard-to-find medicines ranges from basic medicines like the heart medicine nitroglycerin to a lidocaine injection used to numb tissue before surgery.

A deadly meningitis outbreak caused by contamination at a large drug producer could worsen the situation, federal officials have warned. The Food and Drug Administration said that shortages of six drugs — medicines used during surgery and to treat conditions like congestive heart failure — could get worse after a big compounding pharmacy closed over concerns about drug safety. The pharmacy, Ameridose, shares some management with the New England Compounding Center, which is at the center of a meningitis outbreak that has claimed 33 lives.

“When you can’t treat basic things — cardiac arrest, pain management, seizures — you’re in trouble,” said Dr. Carol Cunningham, the state medical director for the Ohio Department of Public Safety’s emergency services division. “When you only have five tools in your toolbox and three of them are gone, what do you do?”

Dr. Margaret A. Hamburg, the FDA commissioner, said in an interview this week that she was “guardedly optimistic” that the shortage crisis was abating.

“I think there’s been an enormous amount of progress,” she said. “We’re seeing real change in the number of shortages that we’re able to recognize early.”

More than 150 new shortages have been prevented this year, according to the agency.

But Erin Fox, who tracks supply levels for a broader range of drugs at the University of Utah, said once a drug became scarce, it tended to stay scarce. The university’s Drug Information Service was actively tracking 282 hard-to-find products by the end of the third quarter of this year, a record.

“The shortages we have aren’t going away — they’re not resolving,” she said. “But the good news is we’re not piling more shortages on top.”

In 2011, prompted by emotional pleas by cancer patients and others who said the drug shortage was threatening lives, President Barack Obama issued an executive order requiring drug makers to notify the FDA when a shortage appeared imminent. The agency also loosened some restrictions on importing drugs and sped up approvals by other manufacturers to make certain medicines.

A law passed this summer contains several provisions aimed at improving the situation, including expediting approval of new generic medicines and requiring the agency’s enforcement unit to better coordinate with its drug-shortage officials before it takes action against a manufacturer.

Federal drug officials trace much of the drug shortage crisis to delays at plants that make sterile injectable drugs, which account for about 80 percent of the scarce medicines. Nearly a third of the industry’s manufacturing capacity is not running because of plant closings or shutdowns to fix serious quality issues. Other shortages have been caused by supply disruptions of the raw ingredients used to make the drugs, or by manufacturers exiting the market.

Some people have accused the FDA of causing the shortages, saying overzealous enforcement and poor communication have led plants to needlessly close or slow production. Others have cited economic factors, like market pressures and reimbursement policies that have set prices so low that some companies have stopped making certain drugs.

Earlier this week, several Democratic members of Congress asked the Government Accountability Office to investigate whether the practices of so-called group purchasing organizations, which buy drugs on behalf of hospitals, were contributing to the shortage.

Regardless of the cause, the drug shortage has forced the FDA to make some tough choices, including allowing manufacturers to sell drugs that, if it were not for the crisis, most likely would have been recalled. Last year, for example, the agency allowed the manufacturer American Regent to sell a drug used during chemotherapy that was found to contain glass particles. Doctors and nurses were instructed to filter the drug, sodium thiosulfate, before administering it.