New OpenPrescribing tool: long-term prescribing trends, back to 1998!

We have created a new interactive tool for exploring the national Prescribing Cost Analysis (PCA) data, allowing you to investigate prescribing trends going back to 1998. The PCA data contains annual data on all drugs dispensed in the community in England. Note this makes it slightly different to the monthly dataset used elsewhere on OpenPrescribing which shows how items were prescribed in England. This means that, for example, in PCA data generic products will not appear until the generic is available to be dispensed, and prescriptions written in Wales will be included provided they were dispensed in England.

One major issue in using data covering so many years is that many drugs have changed name or classification, which can cause time trends to appear disrupted and misleading. For example, many drug and chemical names were changed in 2003 to come in line with International standard spellings; and the BNF classifications are often changed and subdivided to incorporate emergent classes of drugs or changes in usage. Drugs can also move across whole chapters, e.g. melatonin moved from Chapter 9 (Nutrition) to Chapter 4 (Central Nervous System).

To overcome this, we have ensured that drugs have a consistent classification over time, wherever possible, based on their current position in the latest BNF dictionary. All drugs have also been assigned their most up-to-date product and chemical name. In the example below, the chemical name for the product Asilone has changed twice (top), but in our normalised dataset only the latest chemical name is used (bottom).

We have also corrected for two underlying factors which influence all of the data. England’s population rose by 11% from 1998 to 2016 (using ONS mid-year populations), so we have given all figures as per 1,000 population. We also factored in inflation, e.g. prices in 1998 need to be multiplied by 1.40 to make them comparable with 2016 (consumer price index from ONS).

The various tabs each show different visualisations of trends in prescribing:

• Detailed trends for selected chemicals, broken down into products (landing page);
• Chapter trends;
• Section trends for any selected Chapter;
• Sections ranked by items/cost for any selected year;
• Calculation of the change in items/cost for every Section, between any selected year to the latest year;
• The top 20 Paragraphs by number of items and the top 20 by cost.

There is a video demonstrating how to use the first, most detailed part of the tool; or, briefly:

1. Make a selection from any of the drop-down menus, and the table will show all relevant chemicals, by Paragraph, with a square symbol indicating the relative total volume of each.

2. Next, select a paragraph or chemicals in the table to trigger the appearance of stacked charts of trends in items and cost over time. The charts show each chemical in a different colour, with lines to distinguish different products within each chemical, e.g. below you can see branded and generic forms of lanzoprazole and omeprazole.

3. Select chemicals in the above chart to view trends in average cost-per-item and quantity-per-item for all relevant products.

The tool can be accessed at openprescribing.net/pca/. We hope you find it useful and would welcome any feedback on this new feature! Our paper on the tool, on trends, and the underlying data, is currently under review. If you’d like to collaborate on research around this dataset, we know it backwards, so get in touch, and please make sure to cite OpenPrescribing if you use our work, so we can show our funders that you find our output helpful!