Impact of Newer Pharmacological Treatments on Quality of Life in Patients with Parkinson’s Disease

Parkinson’s disease is a common progressive neurodegenerative condition with multiple motor and nonmotor features contributing to impairment of health-related quality of life (HR-QOL). Pharmacological treatments have been directed primarily at dopamine replacement with levodopa and agents to improve its bioavailability, including DOPA decarboxylase inhibitors, catechol-O-methyl-transferase (COMT) inhibitors and monoamine oxidase B (MAO-B) inhibitors, as well as synthetic dopamine agonists. These treatments to restore motor function are often very successful in early Parkinson’s disease, with objective improvement and concomitant improvement in subjective HR-QOL scores. However, as the disease progresses, motor complications and nonmotor symptoms predominate and are often refractory to therapeutic interventions. Antiparkinsonian medications have been shown to improve motor severity and motor complications of advancing disease, and there is increasing evidence that this can be translated into subjective improvement of HR-QOL from a patient’s point of view. However, the degree of improvement is less marked on HR-QOL scores than on motor scores, and some studies do not show improvement of HR-QOL in parallel to motor improvements. A number of explanations are possible, including limitations of the scales used, trial designs and lack of clinical improvement from the patients’ point of view. This review concentrates on clinical trials with an index of HR-QOL as an outcome measure, with particular emphasis on well designed, randomized, double-blind, placebo-controlled or active comparator-controlled methodology. Drugs that have been more recently added to the armamentarium of Parkinson’s disease, including the oral (pramipexole, ropinirole and piribedil) and transdermal (rotigotine) non-ergotamine-derived dopamine agonists, the novel MAO-B inhibitor rasagiline and the COMT inhibitors tolcapone and entacapone, were included. The effect of each of these agents on overall HR-QOL and depression, a factor that has been shown to significantly contribute to HR-QOL in several multivariate analyses, is discussed.