PPU: make it more clear when prices may have changed

[HelenCEBM]

Data in PPU charts shows prices as paid during month of prescribing. Any price changes after the 8th of that month will not have come into effect (will apply in following month). This means people may put time and effort into changing from a brand which has since become cheaper, or onto a brand which has since become more pricey, so effort may have been better spent elsewhere.

Options:

• Make it clearer in charts (e.g. in title) that data applies "for [month year]"
• add a note to say prices may have changed since the 8th of [month]
• (more difficult) link to DMD to show current price / flag if it has changed.

[alexwalkerepi]

Details of when price changes take effect here: https://psnc.org.uk/dispensing-supply/endorsement/how-the-price-change-mechanism-works/

[alexwalkerepi]

Another email relating to differences between PPU prices and current prices:

*AirFluSal prices*

Hi OP 

The PPU data has prices for AirFluSal which are old / greater than the DMD prices? 

Apparently the AirFluSal 125 has been £16.42 since 21.5.19 but shows as 18.50 on OP. 

Same issues on the 250. 
https://apps.nhsbsa.nhs.uk/DMDBrowser/DMDBrowser.do#product
https://openprescribing.net/ccg/15N/0302000N0AABFBF/price_per_unit/?date=2019-04-01

Kind regards 

*Tony Perkins*
Senior Medicines Optimisation Pharmacist West Devon```

[sebbacon]

This is "trivial" as long as we can find a form of words that says it may have changed, and then link to the VMPP page. It's possible that this results in something quite confusing as the VMPP price != the drug tariff price.

[alexwalkerepi]

Is it problematic or confusing to plot the "current" price on the chart?

[HelenCEBM]

Could fix at same time as #1606 if we're just implementing a text fix. E.g.

Please note: prices represent those paid in [month]. For current prices please refer to DM+D, or our [drug tariff tracker] for generic drug prices.

Thoughts @brianmackenna ?