MAOB and Parkinson disease: Levodopa (l-dopa) remains the principal drug used for replenishing reduced DA levels in PD, while adjunct therapeutics include catechol-O-methyl transferase (COMT) inhibitors such as carbidopa, monoamine oxidase B (MAO-B) inhibitors such as selegiline and safinamide, and DA receptor agonists such as pramipexole and apomorphine.