MAO-B

Class

Reversible selective MAO-B inhibitor

Monoamine oxidase B (MAO-B) is a mitochondrial enzyme, most abundant in glial cells of the brain, that breaks down dopamine and related monoamine neurotransmitters through oxidative deamination. Because dopamine signaling is diminished in Parkinson's disease as dopaminergic neurons are lost, inhibiting MAO-B slows the breakdown of the dopamine that remains, helping sustain motor signaling. This is the core biological rationale for selective MAO-B inhibition. Two MAO isoforms exist, MAO-A and MAO-B, with overlapping but distinct substrate preferences; MAO-A in the gut and liver metabolizes dietary tyramine, so agents that also block MAO-A can provoke a dangerous rise in blood pressure after tyramine-containing foods. Selectivity for MAO-B avoids this interaction. Reversibility is a further refinement: reversible inhibitors dissociate from the enzyme, allowing normal monoamine metabolism to resume once the drug clears, whereas older irreversible inhibitors bind permanently and require new enzyme synthesis to restore activity, prolonging any side effects or interactions. Selective, reversible MAO-B inhibition is used in Parkinson's disease, sometimes alongside dopamine-replacement therapies, and is also being explored in other neurodegenerative and cognitive disorders where excessive glial MAO-B activity has been implicated in producing byproducts that may contribute to neuronal stress.