Safer prescription of blood thinning agents

04 September 2018

A collaboration between pharmaceutical companies, pharmacies and authorities has eliminated a common cause of dosing errors involving blood thinning agents.

In collaboration with the pharmaceutical companies Pfizer and LEO Pharma, the Danish Patient Safety Authority and the Danish Medicines Agency have completed a comprehensive project to change the determination of strength of low-molecular weight heparins, which are blood thinning agents commonly used in hospitals. The change implies that the strength of the products is now indicated unambiguously in the prescription systems as international units (IU) per prefilled syringe. A previously frequent cause of dosing errors has thus been eliminated.

In 2013, the Danish Patient Safety Authority began receiving reports on adverse events involving dosing errors with Innohep and Fragmin, and in the beginning of 2015, the authority was also contacted by several regions, which told them about the problem. The Association of Danish Pharmacies further reported that a pharmacy having scrutinised prescriptions for Innohep had found that about 70% of the prescriptions contained errors. 

Against this backdrop, the Danish Patient Safety Authority approached the Danish Medicines Agency, which had already initiated an analysis to find a solution to the problem. The Danish Medicines Agency's analysis and evaluation and its dialogue with the Association of Danish Pharmacies, the hospital pharmacies and others revealed that doctors were unable to distinguish between the different syringes' dosage and thus the actual dose of the needles in their prescription systems, which is what caused the dosing errors. In the worst case scenario, Fragmin or Innohep dosing errors could cause the patient to bleed to death or have a blood clot.

The solution that the Danish Medicines Agency and the manufacturers reached was to split up the existing marketing authorisations and make the indication of strength unambiguous in the doctors' prescription systems. The changes have been implemented stepwise in the period from March to June 2015 for Fragmin and from November 2016 to January 2017 for Innohep.

Henrik Tor Jensen from Humlebæk Pharmacy was one of the proprietary pharmacists who contacted the Danish Patient Safety Authority in 2015 to draw attention to the problem. He no longer sees the type of error that made him react back then. ”Previously, we often spotted errors in the prescriptions and regularly had to contact the doctors to double check their prescriptions, but we have actually not discovered any errors since the changes were implemented. My initial assessment is that it is an example of a recurring error that has more or less been eliminated,” says Henrik Tor Jensen.

Since the changes entered into force, there has been a fall in the number of reports of adverse events involving mix-ups in the prescription of prefilled syringes with different volumes. ”We cannot categorically say why the number of reports has dropped, but there is every reason to be pleased about the constructive collaboration between pharmaceutical companies, pharmacies and authorities. It is a good example of how we can strengthen patient safety together,” says Lena Graversen, Head of Division at the Danish Patient Safety Authority.


Example of an adverse event related to a heparin dosing error 

”The following is prescribed: Fragmin 25,000 anti Xa IU/ml 10 x 0.2 ml at the dose of 0.4 ml (10,000 IU). This is not consistent. When the pharmacy intervenes and corrects the prescription, it is changed to: Fragmin 25,000 anti Xa IU/ml 5 x 0.4 ml, which corresponds to 10,000 IU per dose. The problem was that the doctors were unable to see the different pack sizes and thus the dose in the hospital’s electronic system. The patient suffered no harm.”

Adverse event reported to the Danish Patient Safety Database.