The death of a hospital patient who was given the wrong medication occurred because a pharmacy worker inadvertently filled an IV bag with the wrong drug, officials at an Oregon hospital say.

The mistake was one of several revealed Monday that led to the death of Loretta Macpherson, who had gone to the emergency room at St. Charles Medical Center in Bend.

Officials at St. Charles Health System say Macpherson, 65, was given a paralyzing agent typically used during surgeries instead of the anti-seizure medication that was prescribed for her last week.

Hospital officials say the drug prescribed by the physician, fosphenytoin, was correctly entered into the electronic medical records system and the hospital's pharmacy received the correct medication order.

The IV bag also was correctly labeled. But the hospital's internal investigation revealed that a pharmacy worker inadvertently filled the bag with the wrong drug, rocuronium.

A second worker then reviewed the vials of medication and the IV bag without catching the error.

Shortly after the medication was administered to Macpherson in the ER, a fire alarm led a staff member to lock the door of Macpherson's room "to protect her from potential fire hazards."

Health system spokeswoman Lisa Goodman said Macpherson was in the room for about 20 minutes before a nurse returned to check on her. By that time, the patient had suffered cardiac arrest.

Though doctors were able to resuscitate Macpherson, she had suffered brain damage. She was taken off life support two days later.

Three employees involved in the error have been placed on paid administrative leave.

The health system said in a statement that it has put several measures in place to make sure the mistakes aren't repeated. It's enforcing a "safety zone" in its pharmacies so workers can complete medication verifications with fewer distractions, and it's bringing in an external pharmacy expert to provide recommendations.

The hospital system is also looking at changes in how patients are monitored after medication is administered.

Macpherson, a resident of the small central Oregon town of Sisters, is survived by two sons.

"While human mistakes were made in this case, we as a health system are responsible for ensuring the safety of our patients," the health system said in a statement. "No single caregiver is responsible for Loretta Macpherson's death. All of us in the St. Charles family feel a sense of responsibility and deep remorse."