Dementia in Parkinson disease
Cognitive impairment is common in Parkinson disease, and its prevalence increases with time. Severe dementia is a major cause of disability and mortality in Parkinson disease. The pattern of cognitive impairment is executive dysfunction and impaired visuospatial function, with fewer memory deficits. Language function is preserved.
A systematic review1 of the effect of acetylcholinesterase inhibitors on dementia in Parkinson disease showed mild to moderate benefits. Donepezil and rivastigmine are used most often as they have fewer adverse effects (eg gastrointestinal disturbance, tremors). However, in studies of rivastigmine almost 20% of patients stopped taking the drug because of adverse effects, including worsening tremor. Donepezil and rivastigmine can also improve neuropsychiatric symptoms (eg hallucinations).
As the benefits of an acetylcholinesterase inhibitor are modest, a trial of 2 to 3 months is suggested. Regularly review the patient's response, and stop treatment if they have serious adverse effects or if no benefit is seen (measured by bedside testing or carers' observations). Taper the dose slowly if stopping treatment, to avoid sudden cognitive and behavioural deterioration.
Use:
1 donepezil 5 mg orally, once daily at night for 4 weeks. If tolerated, increase to 10 mg at night. Review after 2 to 3 months dementia (Parkinson disease) donepezil
OR
1 rivastigmine 4.6 mg transdermally, once daily applied for 24 hours. If tolerated, after 4 weeks increase to 9.5 mg daily. If needed, after at least 4 more weeks, increase to 13.3 mg daily. Review after 2 to 3 months2 dementia (Parkinson disease) rivastigmine
OR
2 rivastigmine 1.5 mg orally, twice daily. If needed, every 4 weeks increase dose by 1.5 mg twice daily as tolerated, to a maximum of 6 mg twice daily. Review after 2 to 3 months. rivastigmine