The potential for inappropriate medication prescribing in patients with Parkinson disease and dementia has been highlighted in a US study.
Concurrent prescribing of a high potency anticholinergic medication and an acetylcholinesterase inhibitor (ACHEI) such as donepezil was common but should be a ‘never’ event due to their opposing pharmacologic effects, it found.
And people with Parkinson disease may be particularly vulnerable to adverse effects because of their disease-related disruption of central cholinergic pathways, the study authors warned.
The cross-sectional study of prescription data for 268, 407 people with Parkinson disease found 27% had also filled at least one prescription for a dementia medication.
The most common dementia medications were donepezil (63%), memantine (42%) and rivastigmine (26%). Dual dementia drug therapy, most often donepezil and memantine, was prescribed to 26.7% of the study sample.
Importantly, of the 64,017 patients being treated for dementia with an acetylcholinesterase inhibitor, 81.3% had concurrent use of at least one anticholinergic agent.
Most use was of low potency anticholinergics (68%) – based on their effects on cognition – but 44.5% of use involved high potency anticholinergics.
“We found that sequential high-potency anticholinergic-ACHEI events were common: 17,149 persons (84.9%) who filled a prescription for donepezil and a high- potency anticholinergic drug experienced at least 1 event and 7,305 (84.1%) high-potency anticholinergic-rivastigmine events occurred more than once,” the study said.
The study found co-administration of a high-potency anticholinergic and an ACHEI was associated with comorbidities such as depression, COPD, hypertension, chronic kidney disease, diabetes and heart failure.
For example, tricyclic antidepressants and paroxetine used for depression are considered high potency anticholinergic medications.
“Thus, comorbid condition guidelines may be the initial intervention targets for reducing inappropriate prescribing in Parkinson disease.”
The study was unable to examine over-the-counter anticholinergic drugs so may have underestimated the size of the problem.
However an editorial in JAMA Neurology cautioned that it was difficult to interpret whether prescribing practices were inappropriate when working with a medical claims database.
The authors said further problems occur in the application of scales such as the Anticholinergic Cognitive Burden (ACB) Scale to Parkinson disease, which often requires an individualised patient approach.
“In patients with Parkinson disease-related psychosis, both clozapine and quetiapine fumarate are commonly prescribed and are standard-of-care treatments for severe and refractory symptoms.”
“Yet both drugs have an ACB score of 3, and thus the methods of Mantri and colleagues would classify their use in this cohort as prescribing errors and never events.”