Selegiline

Selegiline, also known as L-deprenyl, is a selective inhibitor of the enzyme monoamine oxidase B (MAO-B) used in the management of Parkinson's disease and, in transdermal form, major depressive disorder as an augmentation strategy. It is available as oral tablets and as a selegiline transdermal system (a patch).

The primary mechanism is the inhibition of MAO-B, which slows the breakdown of dopamine in the brain and thus increases dopaminergic activity. At higher systemic concentrations, selegiline can inhibit MAO-A as well, which raises the risk of hypertensive reactions with tyramine-containing foods or certain drugs.

In Parkinson's disease, selegiline is used as monotherapy in early stages and as an adjunct to levodopa to improve motor symptoms and extend the effect of levodopa. In depression, the transdermal patch is approved as an augmentation option for adults taking antidepressants, particularly SSRIs or SNRIs, though its use requires awareness of potential drug and dietary interactions.

Common adverse effects include dizziness, orthostatic hypotension, nausea, insomnia, and dyskinesias; the patch can cause local skin reactions. Serious but uncommon risks include hypertensive crisis with dietary tyramine or certain sympathomimetics, and serotonin syndrome when combined with serotonergic medications.

Selegiline is metabolized in the liver to active amphetamine- and methamphetamine-like metabolites, contributing to stimulant‑type effects in some patients. Contraindications include concurrent nonselective MAO inhibitors, untreated pheochromocytoma, and known hypersensitivity. Caution is advised in older adults and in individuals with cardiac or hepatic impairment.

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