OBJECTIVES: The objective of this study was to quantify the expenditure of products that have gone off-patent since 2012 and to estimate the savings after loss of exclusivity.

METHODS: Molecules that have gone off-patent since 2012 and for which a generic or biosimilar was introduced in the Netherlands were identified. For outpatient drugs, data on the usage and reimbursement were obtained from the publicly available GIP Open Data. For inpatient drugs, reimbursement data were also obtained from the GIP Open Data, whereas the usage was informed from the IQVIA SAMOL database. The average reimbursement per daily defined dose (DDD) was calculated per calendar year and used to inform a model to quantify the expenditure after loss of exclusivity. Results were presented in the form of relative difference in expenditure per DDD and savings due to patent expiration.

RESULTS: Five years after loss of exclusivity, an expenditure erosion of 40% was found for all molecules that have gone off-patent since 2012. Inpatient molecules witnessed a higher erosion (57%) compared to outpatient molecules (38%). If corrected for relative usage, the weighted expenditure erosion increased to 63%, which was also found to be higher for inpatient molecules (88%) than for outpatient molecules (62%). Stratified analyses show that recently expired molecules witnessed a more rapid decline in expenditure per DDD. Reductions in expenditure did not immediately translate into savings in all cases, as some molecules experienced an increase in use after loss of exclusivity.

CONCLUSIONS: Trends were found in expenditure after loss of exclusivity, with the highest erosion observed in the first three years after patent expiration, after which a plateau formed. This study also provides evidence that the rate of erosion has recently increased which may suggest that payers have become increasingly successful over time in negotiating price reductions after loss of exclusivity.