Consumption of oral anticancer drugs in Norway compared by different units of measurements – introduction of new DDDs

Background: Antineoplastic agents (ATC group L01) have not been assigned DDDs due to highly interindividualvariation in dosages. Consumption data has therefore been presented in other measurement units such as grams of active ingredient. However, the protein kinase inhibitors (PKIs) are a rapidly growing drug group that was introduced to the market recently and are administered orally in a fixed dose. DDDs were therefore established for the PKIs in 2020. In this study we aim to assess whether the newly assigned DDDs would better express drug utilisation patterns in Norway than the current units of measurement.Methods: Sales data for PKIs (ATC level L01E) by grams, cost, units and packages for 2019 were collectedfrom the Norwegian Drug Wholesales Statistics and data on number of prescriptions and prevalence for 2019were collected from the Norwegian Prescription Database (NorPD). DDDs were calculated by applying thevalues of the new DDDs.Results: The proportions of the different substances varied according to the unit of measurement. DDDs andpackages had the highest similarity and correlated better than grams with the prevalence of use in theNorwegian population. BCR-ABL tyrosine kinase inhibitors was the largest group accounting for 31% ofthe total consumption (DDD/1000 inhabitants/day) and imatinib was the most sold PKI in all units of measurement except cost.Conclusions: Using an international agreed unit of measurement gives reliability to the study result. Assignment of DDDs to PKIs will improve the quality of drug utilisation studies in this area.