Antipsychotic prescribing to patients diagnosed with dementia without a diagnosis of psychosis in the context of national guidance and drug safety warnings: longitudinal study in UK general practice

Introduction
Policy interventions to address inappropriate prescribing of antipsychotic drugs to older people diagnosed with dementia are commonplace. In the UK warnings were issued by the Medicines Healthcare products Regulatory Agency (MHRA) in 2004, 2009 and 2012 and National Institute for Health and Care Excellence (NICE) guidance was published in 2006. It is important to evaluate the impact of such interventions.

Methods
We analysed routinely-collected primary-care data from 111,346 patients attending one of 689 general practices contributing to the Clinical Practice Research Datalink to describe the temporal changes in prescribing of antipsychotic drugs to patients aged 65 years or over diagnosed with dementia without a concomitant psychosis diagnosis from 2001 to 2014 using an interrupted time series and a before and after design. Logistic regression methods were used to quantify the impact of patient and practice level variables on prescribing prevalence.

Results
Prescribing of first-generation antipsychotics reduced from 8.9% in 2001 to 1.4% in 2014 (prevalence ratio 2014/2001 adjusted for age, gender and clustering within practices (0.14, 95% CI 0.12 to 0.16) whereas there was little change for second generation drugs (1.01, 0.94 to 1.17). Between 2004 and 2012 several policy interventions coincided with a pattern of ups and downs whereas the 2006 NICE guidance was followed by a gradual, longer term, reduction. Since 2013 the decreasing trend in second-generation antipsychotic prescribing has plateaued largely driven by increasing prescribing of risperidone.

Conclusions
Increased surveillance and evaluation of drug safety warnings and guidance is needed to improve the impact of future interventions.