Review: Improving symptom control in early Parkinson’s disease

Abstract

Motor symptoms in Parkinson’s disease (PD) are caused by a severe loss of pigmented dopamine-producing nigro-striatal neurons. Symptomatic therapies provide benefit for motor features by restoring dopamine receptor stimulation. Studies have demonstrated that delaying the introduction of dopaminergic medical therapy is associated with a rapid decline in quality of life. Nonmotor symptoms, such as depression, are common in early PD and also affect quality of life. Therefore, dopaminergic therapy should typically be initiated at, or shortly following, diagnosis. Monamine oxidase-B inhibitors provide mild symptomatic benefit, have excellent side effect profiles, and may improve long-term outcomes, making them an important first-line treatment option. Dopamine agonists (DAs) provide moderate symptomatic benefit but are associated with more side effects than levodopa. However, they delay the development of motor complications by delaying the need for levodopa. Levodopa (LD) is the most efficacious medication, but its chronic use is associated with the development of motor complications that can be difficult to resolve. Younger patients are more likely to develop levodopa-induced motor complications and they are therefore often treated with a DA before levodopa is added. For older patients, levodopa provides good motor benefit with a relatively low-risk of motor complications. Using levodopa with a dopa-decarboxylase inhibitor lessens adverse effects, and further adding a catechol-O-methyl transferase inhibitor can improve symptom control.