The UK government has an excellent policy of making data more open and easier to access. See:
http://data.gov.uk

As part of this policy, prescription data has been released broken down by GP practice and drug. There is a mass of detail: a single month has over 4,000,000 rows of data. This is too much for my version of Excel to cope with, so I've written a program in PHP to analyse the data for England for June 2012. (Note: England, not UK. Under devolution the other parts of the UK report separately.) Along with totals, the report shows for each "Parkinson's drug" the number of prescriptions written for it and the cost to the NHS.

Note 1. The drugs listed below can be used for PD, but some can be used for other conditions as well. It is not possible to extract these out.

Note 2. I take the "Total Items" figure to represent the number of prescriptions written for this drug regardless of size, duration, and dose. For instance, a week's worth of ropinirole, 2mg, and a month's worth of ropinirole, 16 mg, both count one. For a disease like Parkinson's, I would expect the average duration to be close to one month.

(My apologies, I've not been able to format the table here.)

The results show total monthly drug costs to the NHS of £609m, of which £7m is spent on "PD" drugs. (Note: this is not the same as saying the monthly drug costs of PwP in England is £7m: these will be higher because they include a wider range of drugs.)

*** REPORT ************************************************** *************
NHS England, prescription data, June 2012.
Number rows = 4082592
Raw data from file T201206PDPIEXT.CSV obtained from:
http://data.gov.uk/dataset/gp-practice-prescribing-data
'All prescribed and dispensed medicines (by chemical name), dressings and appliances (at section level)
are listed for each GP practice. -For each GP practice, the total number of items that were prescribed and
then dispensed is shown. -The total Net Ingredient Cost and the total Actual Cost of these items is shown. '
Available under Open Government Licence, details:
http://www.nationalarchives.gov.uk/d...nment-licence/

Drug Code, Drug Name,Total items, NIC, Actual cost
TOTAL,TOTAL,78609510,658805466.87994,609262986.319 61
including
0409010A0,Apomorphine Hydrochloride ,935,567602.58,522883.13
0409010B0,Amantadine Hydrochloride ,8833,81237.74,75085.77
0409010H0,Ropinirole Hydrochloride ,38929,1045358.2,964080.86
0409010I0,Levodopa ,2,206.49,190.27
0409010K0,Co-Beneldopa (Benserazide/Levodopa) ,58354,369203.01,341836.19
0409010N0,Co-Careldopa (Carbidopa/Levodopa) ,69102,1017974.1,939828.93
0409010P0,Pergolide Mesilate ,293,12049.69,11108.67
0409010S0,Tolcapone ,123,10450.15,9630.1
0409010T0,Selegiline Hydrochloride ,4334,54446.67,50280.85
0409010U0,Cabergoline ,651,72850.12,67125.93
0409010V0,Entacapone ,4344,228720.91,210818.35
0409010W0,Pramipexole ,26646,1466118.42,1351319.57
0409010X0,Levodopa/Carbidopa/Entacapone ,14663,960851.9,885533.31
0409010Y0,Rasagiline Mesilate ,9484,723728.28,666954.52
0409010Z0,Rotigotine ,5756,748280.54,689465.7
0409020C0,Trihexyphenidyl Hydrochloride ,7742,83730.04,77368
0409020E0,Benzatropine Mesilate ,39,1914.38,1764.72
0409020N0,Orphenadrine Hydrochloride ,5996,194940.02,179758.82
0409020S0,Procyclidine Hydrochloride ,65514,210941.41,196403.17
PDTOTAL,PDTOTAL,321740,7850604.65,7241436.86
Note some of the 'PD' drugs may be used for other conditions as well.

While checking that I'd got my facts right I came across this paper:
"Prescription Cost Analysis England 2011"
Health and Social Care Information Centre. Prescribing and Primary Care Services
http://www.ic.nhs.uk/webfiles/public...011_report.pdf
This gives even more detail: a breakdown by brand and dose.

My next step is to extract out data by location to see if there's any geographical variations in the prevalence of PD in England.

John