Polypharmacy in Chronic Neurological Diseases: Multiple Sclerosis, Dementia and Parkinson's Disease.

Polypharmacy is an important aspect of medication management and particularly affects elderly and chronically ill people. Patients with dementia, Parkinson's disease (PD), or multiple sclerosis (MS) are at high risk of multi medication due to their complex symptomatology. Our aim was to provide an overview of different definitions of polypharmacy and to present the current state of research on polypharmacy in patients with dementia, PD, or MS. The most common definition of polypharmacy in the literature is the concomitant use of ≥5 medications (quantitative definition approach). Polypharmacy rates of up to >50% have been reported for patients with dementia, PD, or MS, although MS patients are on average significantly younger than those with dementia or PD. The main predictor of polypharmacy is the complex symptom profile of these neurological disorders. Potentially inappropriate medication (PIM), drug-drug interactions, poor treatment adherence, severe disease course, cognitive impairment, hospitalisation, poor quality of life, frailty, and mortality have been associated with polypharmacy in patients with dementia, PD, or MS. For patients with polypharmacy, either the avoidance of PIM (selective deprescribing) or the substitution of PIM with more suitable drugs (appropriate polypharmacy) is recommended to achieve a more effective therapeutic management.