What is the impact of regulatory guidance and expiry of drug patents on dementia drug prescriptions in England? A trend analysis in the Clinical Practice Research Datalink

Background: Drugs for dementia have been available in England from 1997. Since their launch, there have been several changes to national guidelines and initiatives that may have influenced prescribing. These include changes in National Institute for health and Care Excellence (NICE) guidance; several government dementia strategies; the addition of dementia to the Quality and Outcomes Framework (QOF); and the expiry of drug patents. Despite this, there has been little research into the effect of these events on prescribing. This paper examines prescribing trends in England using data from the UK Clinical Practice Research Datalink since the launch of drugs for dementia up to 1st January 2016.

Methods: We considered the monthly proportion of patients eligible for treatment, with a diagnosis of probable Alzheimer’s disease, receiving their first prescription for each drug class – namely acetylcholinesterase (AChE) inhibitors (donepezil, rivastigmine, galantamine) and N-Methyl-D-aspartate (NMDA) receptor antagonists (memantine). Trend analysis using joinpoint models was then applied to identify up to two trend changes per treatment of interest.

Results: The overall trend was for increasing prescriptions in each drug class over the period they were studied. This was indicated by the average monthly percentage change, which was 6.0% (95% CI: -6.4 to 19.9; June 1997 to December 2015) for AChE inhibitors and 15.4% (95% CI: -77.1 to 480.9; January 2003 to December 2015) for NMDA receptor antagonists. Prescriptions of AChE inhibitors increased at the end of 2012, probably in response to the patent expiry of these drugs earlier that year. The Prime Minister’s Dementia Challenge launched in May 2012 may also have contributed to the observed increase. However, neither this strategy nor patent expiry appeared to influence prescriptions of NMDA receptor antagonists. Instead trend changes in this drug class were driven by NICE guidance released in 2011 that allowed access to these drugs outside of clinical trials.

Conclusions: Dementia drug prescribing does not always respond to factors such as regulatory guidance, recommendations or patent expiry and, when it does, not necessarily in a predictable way. This suggests that improved communication with clinicians may be needed to improve the cost-effective use of drugs for dementia.