The Role of Monoamine Oxidase B Inhibitors in the Treatment of Parkinson’s Disease – An Update

Parkinson's disease (PD) is a progressive neurodegenerative disease characterised by reduced dopamine level in the substantial nigra. This may lead to typical motor features such as bradykinesia, resting tremors and rigid muscles; as well as non-motor symptoms such as neuropsychiatric symptoms, sleep disorders, autonomic dysfunction, and sensory disturbances. Inhibitors of MAO-B are used to alleviate symptoms by reducing monoamine oxidase-catalysed degradation of dopamine; hence, preserving functional levels of dopamine. The very first MAO-B used therapeutically was selegiline, followed by rasagiline, its indane derivative which has superior efficacy and selectivity. Both inhibitors can be used as monotherapy or in combination with other anti-Parkinson drugs. Safinamide, a reversible MAO-B inhibitor that utilises both dopaminergic and non-dopaminergic mechanisms, was recently approved by the European Medicines Agency (EMA) (2015) and U.S. FDA (2017) as an add-on therapy for patients with mid- or late-stage Parkinson’s disease. Furthermore, MAO-B inhibitors were found to be associated with potential neuroprotective and disease modifying effects. However, evidence of their efficacy and role in PD models are scarce and warrants further investigation.