A shortage of a drug used to treat children with cancer is in short supply, meaning that doctors may have to ration it.

The drug is known as Vincristine and it is used in chemotherapy for leukemia, brain tumors, lymphomas and other cancers. Doctors say that it is an irreplaceable part of the treatment.

But only two companies make the drug and the Food and Drug Administration says that one of the companies stopped making it for business reasons.

Only the company Pfizer continues to make the drug, but the company is having manufacturing difficulties.

Doctors say that they have some hard choices to make.

"Unfortunately, with Vincristine we don't have a substitute in case we have a shortage. So, it may impact the health of children with cancer,” says Dr. Nibal Zaghloul of Saint Peter’s University Hospital.

Doctors could be forced to reduce or skip doses for their patients.