The Impact on Health Outcomes and Healthcare Utilisation of Switching to Generic Medicines Consequent to Reference Pricing: The Case of Lamotrigine in New Zealand
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Many countries have implemented generic reference pricing and substitution as methods of containing pharmaceutical expenditure. However, resistance to switching between medicines is apparent, especially in the case of anti-epileptic medicines.
This study sought to exploit a nation-wide policy intervention on generic reference pricing in New Zealand to evaluate the health outcomes of patients switching from originator to generic lamotrigine, an anti-epileptic medicine.
A retrospective study using the national health collections and prescription records was conducted comparing patients who switched from originator brand to generic lamotrigine with patients who remained on the originator brand. Primary outcome measures included switch behaviour, changes in utilisation of healthcare services at emergency departments, hospitalisations and use of specialist services, and mortality.
Approximately one-quarter of all patients using the originator brand of lamotrigine switched to generic lamotrigine, half of whom made the switch within 60 days of the policy implementation. Multiple switches (three or more) between generic and brand products were evident for around 10 % of switchers. Switch-back rates of 3 % were apparent within 30 days post-switch. No difference in heath outcome measures was associated with switching from originator lamotrigine to a generic equivalent and hence no increased costs could be found for switchers.
Switching from brand to generic lamotrigine is largely devoid of adverse health outcomes; however, creating an incentive to ensure a greater proportion of patients switch to generic lamotrigine is required to achieve maximal financial savings from a policy of generic reference pricing.
KeywordsLamotrigine Reference Price Generic Substitution Chronic Disease Score Originator Brand
The authors would like to acknowledge the support of the Information Analysts in the New Zealand Ministry of Health’s Health Statistics section in the data retrieval process, and the assistance of Joanna Stewart (Epidemiology and Biostatistics Section, School of Population Health, University of Auckland) with earlier drafts of the manuscript and the reviewers for their comments. This study was conducted as part of the requirements towards the attainment of a PhD, and the candidate (CL) has received a University of Auckland Scholarship. CL was the primary developer of the study design and data analysis. All authors reviewed and discussed the study results, and contributed to writing and editing the manuscript. CL is the guarantor of this work and, as such, had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. The final version is approved by all authors, who declare they having no conflict of interests.
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