Ontario Premier Kathleen Wynne said it's "unacceptable" that hundreds of chemotherapy patients received weak doses of medication and that the province will appoint an independent third party to aid its investigation.
"It's unacceptable that this should have happened, that the doses would not have been accurate," the Premier said at the opening of a new breast cancer centre at a Toronto hospital.
She said the province is working to uncover what happened and whether there are any systematic problems that led to the error.
Nearly 1,200 cancer patients at five hospitals in Ontario and New Brunswick are learning that the chemotherapy medication they received were diluted. The drugs are cyclophosphamide and gemcitabine, which are used in breast and lung cancer treatment as well as other types of cancer.
It's unclear what, if any, health implications the mix-up will have for these patients, but the news has led to widespread concern among patients and their families and is raising larger questions about checks and balances in the system.
Wynne advised affected patients to speak to their oncologists to determine what the next course of action should be.
Chemotherapy drugs are given intravenously and the medication is diluted with a saline solution to provide the right dose.
The central question is how the underdosing occurred. Cancer Care Ontario said hospitals purchased the premixed drugs from a company that produces and labels the medications.
Marita Zaffiro, president of Marchese Hospitals Solutions, which supplied the medications, said the problem is not how the drugs were prepared but in how they were administered. The company fulfilled its contractual obligations to the hospitals, the statement said.
The Institute for Safe Medication Practices Canada, an advocacy group, said the incident highlights major problems with the lack of standardization for labelling of IV bags.
The organization said that many commercially available IV bags that come pre-filled with a saline solution include an overfill volume. But if the bags are not labelled to indicate that the volume includes overfill, then any drug added to it will be automatically diluted. It's a serious issue and a national labelling standard is required to prevent this in the future, the group said.
No third party has been chosen yet to conduct the investigation, Ontario officials said.
Ontario Health Minister Deb Matthews said the priority is helping affected patients and that oncologists are working evenings and weekends to accommodate them. She said the Ontario College of Pharmacists was at Marchese Hospital Solutions Wednesday and that Health Canada is involved in the investigation.
"We have to ask the question is this a system issue or is it a one incident issue," Matthews said.