Selegiline is a selective, irreversible MAO-B inhibitor at doses ≤10mg, with 2.5mg being sufficient for full MAO-B blockade, any higher is wasteful. Staying selective at this dose means no dietary tyramine restrictions. Beyond the MAOI mechanism, selegiline has catecholamine activity enhancing (CAE) effects that are actually more pharmacologically interesting: it enhances spontaneous catecholaminergic neuronal activity in a way that amplifies task-relevant function rather than forcing global arousal. Metabolizes to small amounts of L-amphetamine and L-methamphetamine, producing noticeable psychomotor stimulation and mood boost in the first few days , this develops rapid tolerance. What persists after that is more subtle: focus enhancement, motivation support, antidepressant action, and neuroprotection. The CAE effect is the primary long-term value over the MAOI mechanism.
Rapid tolerance to the stimulant/mood effects. Persistent focus/motivation benefits are real but diminished. CAE is more valuable than the MAOI action.