Nearly 1,200 patients in Canada received lower doses of their cancer drugs as a result of poor communication between a compounding pharmacy supplier and several hospitals that utilized the service. The drugs were cyclophosphamide and gemcitabine, used as part of a regimen for breast and lung cancer as well as lymphoma and leukemia. Patients received watered down doses for about a year without anyone realizing there was more saline solution in the bags than stated on the label. Finally, a pharmacy technician at one of the hospitals noticed more fluid in the bags than expected and brought it to the attention of others.
When preparing chemotherapy, cancer drugs are added to ready-to-use intravenous fluid bags from a manufacturer, but the bags typically hold a greater volume of diluent than stated on the label, a situation known as "overfill." Overfill takes into account that some evaporation might occur from the plastic bags and also that some fluid will be left in IV tubing after injection. Additional fluid is also added to the individual cancer drug vials to make a solution out of the powder inside before adding them to the bag.
About a year ago, the hospitals stopped outsourcing chemotherapy preparation from a pharmacy they'd worked with previously and contracted with a new provider. In this recent incident, the new pharmacy labeled the product differently than in the past. The total amount of drug in the bag was labeled correctly but the final drug concentration listed on the label did not take overfill into account.
The bags actually contained several doses of medication that the hospital used to prepare chemotherapy for different patients. What they didn't know was the drugs were from 3% to 20% more diluted than labeled. The failure to understand the final concentration resulted in hospital staff withdrawing less fluid, and therefore less of the cancer drug from the bags than was actually needed for each dose. Thus, some patients received a lower drug amount than intended.
All of the patients have been informed by the hospitals. Management of any overfill volume is perceived to be more critical for oncology medications because the dosing of these drugs is specific to each individual patient and the type of cancer being treated. Although the overall impact is unclear, one can only imagine how distressed the patients and families must be. Most cancer experts do not believe the medication error will have any adverse effects on their overall treatment.
In the US, hospitals and clinics that care for cancer patients generally prepare their own chemotherapy doses and don't use multiple dose source containers of chemotherapy from an outside pharmacy. However, overfill is still an issue even when bags contain a single dose. In the US, most hospitals simply label the bags with the amount of drug added and the total volume (including estimated overfill). So nurses know exactly how much to infuse to get the whole dose in.
But not every hospital or even every pharmacist does it this way. Some hospitals remove the excess fluid from the manufacturer's bag or start with an empty bag to begin with the exact amount of fluid. In a recently released International Medication Safety Self Assessment® for Oncology developed jointly by ISMP in the United States and ISMP Canada, the use of overfill was identified as a point where safeguards may be required. Some hospitals told us that the way they do it hasn't been standardized at all. Thus some pharmacists do it one way while others use different method. This can easily lead to confusion and errors. A good example is a case I wrote about earlier where a little girl named Emily Jerry died after getting too much saline solution. A contributing factor was the nonstandard way of preparing and labeling chemotherapy.
It's clear that an opportunity exists to create and implement national standards for labeling containers that contain overfill volume. We are working with our colleagues in the US and Canada in this regard to develop recommendations for standard labeling practices.