Prescribing of some generic Parkinson’s medicines has increased by more than 45% between 2017 and 2021, analysis carried out by The Pharmaceutical Journal has revealed.
In contrast, prescribing of some doses of the branded drug Sinemet (Carbidopa/levodopa; Organon Pharma UK), decreased by a third over the same time period.
Experts have said that while a move to generic prescribing was necessary to cope with past shortages of Sinemet — most recently in 2020 — the trend could also reflect a push from clinical commissioning groups (CCGs) for clinicians to prescribe cheaper generic medicines.
The data was obtained from the NHS Business Services Authority’s monthly prescription cost analysis, which provides details of the costs and volumes of all prescriptions dispensed in the community in England between 2008 and 2021.
Analysis of the data carried out by The Pharmaceutical Journal revealed that, between 2017 and 2021, prescribing of 25mg/100mg co-careldopa increased from 240,817 items to 350,479 items; an increase of 46%. Prescribing of 12.5mg/50mg co-careldopa also increased significantly over this time period, rising from 191,026 items in 2017 to 223,562 items; an increase of 17%.
In contrast, prescribing of 125mg Sinemet Plus dropped sharply, from 288,878 items in 2017 to 193,100 items in 2021; a fall of 33%. Prescribing of 12.5mg/50mg Sinemet decreased significantly two years before, from 268,848 in 2015 to 141,186 in 2017; a decrease of 48%.
Prescribing of only one branded medicine — Half Sinemet CR (controlled release) tablets 125mg —increased significantly between 2017 and 2021; rising by 124% from 106,528 items to 238,959.
“There is likely more than one reason for the increase in generic prescribing,” said Janine Barnes, neurology specialist pharmacist at The Dudley Group NHS Foundation Trust and founder of the Parkinson’s Disease Specialist Pharmacy Network.
“Since Sinemet shortages began in 2018 but generic prescribing increases started around 2015, we think that CCGs probably were suggesting changes from branded to generic on prescriptions as the generic was likely to be cheaper.
“As Sinemet stopped being manufactured, there became no Sinemet supply of certain strength tablets, so only generic versions were available, hence the rise in the most popular co-careldopa dose of 25mg/100mg tablets.”
Barnes said the figures could also be “distorted” by the fact that, as certain strengths of Sinemet tablets became unavailable, doses were made up with alternative strengths to make up the correct dose.
Laura Cockram, head of policy and campaigning at Parkinson’s UK, said it was “vital” for prescribers to specify the Parkinson’s medication brand or generic manufacturer on prescriptions for people with Parkinson’s disease.
“If a patient has been started on Sinemet by their consultant, this should not be changed to a generic version by their GP without discussing the change with the consultant and the person with Parkinson’s.
“Any changes to brands or manufacturers can trigger a significant deterioration of symptoms and as such should be discussed with the person with Parkinson’s and their consultant.”
In January 2023, a press release published by Parkinson’s UK, revealed that patients had been left with “devastating effects” after being given prescriptions for a mixture of both Sinemet and its generic version, co-careldopa; with some patients not consulted about the change before it happened.
The charity cited the example of one patient, who had lived well with Parkinson’s disease for 17 years, developed slow speech, and was left in pain and an uncontrolled tremor after his normal branded medication was switched to generic co-careldopa.
Data collated for other doses of the drug, such as 25mg/250mg and 10mg/100mg Sinemet and generic co-careldopa, suggest that these are rarely prescribed to patients.