Feb. 10, 2012  -- Medication used to treat the most common form of childhood leukemia is in short supply, adding to the largest nationwide shortage of critical lifesaving hospital medications in nearly a decade.

All five pharmaceutical companies that make the injection drug methotrexate, which treats acute lymphoblastic leukemia by slowing the growth of cancer cells, have either slowed and stopped manufacturing of the drug, according to the U.S. Food and Drug Administration. The companies have cited high demand or manufacturing delays as reasons for the shortage.

If the shortage continues, physicians and pharmacists fear thousands of children will be left without lifesaving treatment.

"This, to us in oncology, is a national crisis," said Brooke Bernhardt, clinical pharmacy specialist in the department of hematology and oncology at Texas Children's Hospital in Houston.

According to Dr. Michael Link, pediatric oncologist and president of the American Society of Clinical Oncology, some hospital pharmacies have reported having only a couple weeks of supply left.

Many oncologists are especially worried about the shortage of the preservative-free form of methotrexate, which is considered less toxic.

Only the preservative-free methotrexate can be injected into the spinal fluid of cancer patients to prevent the spread and recurrence of the disease.

"There are couple other drugs that can be injected into the spinal fluid, but none that are as effective," said Link. "As for the high dose version of the drug, there's no workaround for it."

Each year, nearly 3,000 children and adolescents under age 20 are diagnosed with acute lymphoblastic leukemia in the United States, according to the National Cancer Institute. Eighty percent of children are successfully treated.

The agency said it's uncertain when the next batch of methotrexate will be available.

Drugs for heart patients, some antibiotics, and intravenous drugs have been hard for hospitals to find, but cancer drugs have arguably taken the hardest hit.

"We can't continue in this mode of going from crisis to crisis," said Link.

To compensate, some physicians have had to split vials among patients or use comparable medications. In some cases, physicians may triage the medication, delaying treatment for some who may not need it immediately.

"You're always faced with the problem of whether you can use something else that might work," said Link. "You know in your heart that you're compromising on the cure rate."

President Obama issued an executive order in October 2011 to reduce the dire shortage. The order instructed the Food and Drug Administration to broaden reporting of potential drug shortages, expedite regulatory reviews that can help prevent shortages, and examine whether potential shortages have led to price gouging.

The drug shortage has compromised or delayed care for some patients and may have led to otherwise preventable deaths.

"What we would expect from that order is some help," said Link. "The big problem is that I don't think it can have impact on current shortages right now."

While the FDA can oversee imports of drugs that are in short supply, it cannot regulate how much a company can make. In fact, manufacturers are not required to report shortages to the FDA.

The amount of a drug made available within a hospital is set by an agreement between the hospital and the manufacturer.

Limited manufacturing, lagging production time and lack of profits from these drugs contribute to the shortages. The production costs for some drugs can outweigh the money that companies can make from them, since many drugs now have cheaper generic alternatives. So manufacturers stop making the drugs.

Since these medications are mainly housed in hospitals, most patients won't know they can't have them until they really need them.

"Many physicians may be willing to mention the shortage to the family because they're just as frustrated," said Bernhardt.

However, Bernhardt said, that supply counts depend on location. Some hospitals may not be experiencing a shortage at all, she said.

"We don't want to stir up fear, but [families] should remain in contact with their physician," said Bernhardt.