Price versus clinical guidelines in primary care statin prescribing: a retrospective cohort study and cost simulation model

Abstract

Objective: To investigate the relative impact of generic entry and National Institute for Health and Care Excellence clinical guidelines on prescribing using statins as an exemplar.

Design: Retrospective analysis of statin prescribing in primary care and cost simulation model.

Setting: Royal College of General Practitioners Research and Surveillance Centre (RCGP R&SC) database and Prescription Cost Analysis (PCA) database.

Participants: New patients prescribed statins for the first time between July 2003 and September 2018.

Main outcome measures: Shares of new patients prescribed one of the five statins available in the British National Formulary, and cost of prescribing statins to new and existing patients in primary care in England.

Results: General trends of statin' prescriptions were largely driven by a decrease in acquisition costs triggered by patent expiration, preceding NICE guidelines which themselves did not seem to affect prescription trends. Significant heterogeneity is observed in the prescription of the most cost-effective statin acrossGPs. A cost simulation shows that, between 2004 and 2018, the NHS could have saved £2.8bn (around 40% of the £6.3bn spent on statins during this time) if all GP practices had prescribed only the most cost-effective treatment.

Conclusions: There is potential for large savings for the NHS if new and, whenever possible, ongoing patients are promptly switched to the first medicine that becomes available as generic within a therapeutic class as long as it has similar efficacy to still-patented medicines.

Keywords: clinical guidelines; patent expiration; prescribing behaviour; statins.

Figure 1.

Trends in the statins prescribed for drug treatment initiation. (a) Proportion of new patients on each drug. (b) Average acquisition cost per defined daily dose (DDD) of each drug. Panel (a) shows the proportion of new patients starting drug treatment with each statin over time. The main five events are marked with vertical lines and small squares. The two vertical red lines marks the patent expiration of Zocor (simvastatin) and Lipitor (atorvastatin) in 2003 and May 2012, respectively; and the grey vertical lines indicate the publishing date of NICE’s statin-related national guidance. Panel (b) shows the average acquisition cost per DDD for each statin over time. Statins’ DDDs (or daily strength per day of treatment) established by the WHO are the following: for atorvastatin, 20 mg; fluvastatin 60 mg; pravastatin 30 mg; rosuvastatin 10 mg; and simvastatin 30 mg. Costs are obtained from Net Ingredient Cost figures from PCA, and are expressed in constant 2018 GBP using the GDP deflators at market prices, and money GDP from https://www.gov.uk/government/statistics/gdp-deflators-at-market-prices-and-money-gdp-march-2019-spring-statement. Source: Panel (a) from RCGP R&SC database, and panel (b) from Prescription Cost Analysis data series.

Figure 2.

Heterogeneity in initial prescriptions at the general practice level. (a) Proportion of new patients on simvastatin with quantiles calculated quarterly. (b) Proportion of new patients on Simvastatin with fixed quantile composition calculated on Q3-2003. Panel (a) shows the average proportion of new patients treated with simvastatin within five quintiles of general practices ranked by proportion of simvastatin prescriptions (e.g. the top line represents the average proportion of patients initially treated with simvastatin, by the top 20th percent of general practices, etc.), where the quintiles of practices are obtained separately for each month (i.e. practices in each quantile may be different). Panel (b) shows the average proportion of new patients treated with simvastatin but for quintiles of practices obtained at Q3-2003, (i.e. the practices in each quintile are the same). Source: RCGP R&SC database.

Figure A1.

Volume of statins prescribed in main data sources. (a) Prescription Cost Analysis data. (b) RCGP R&SC data.