Selegiline is used either alone or in combination with levodopa or levodopa/carbidopa to treat the symptoms of Parkinson's disease. This medicine helps to increase and extend the beneficial effects of levodopa. Selegiline has also been used to treat depression.
Selegiline has been used since 1975 as adjunctive therapy for Parkinson's disease. Selegiline blocks the enzyme monoamine oxidase type B, which forms one of the metabolic pathways for dopamine in the brain. It was predicted that selegiline would prolong the effect of native or endogenous dopamine, and also prolong the effect of dopamine formed from therapeutically administered levodopa.
In the 1980s, evidence suggested that selegiline may retard the pathological process that leads to the development of Parkinson's disease. Two possible mechanisms were postulated. The most popular was the blockade of oxidation and, therefore, free radical formation. A less popular putative mechanism was that selegiline may prevent the action of environmental toxins.
While most observers now accept that selegiline does not have a neuroprotective effect, there is still a body of animal studies supporting this possibility, and some clinicians have continued to argue that selegiline may retard the progression of Parkinson's disease.
There is no longer any compelling reason to prescribe selegiline as sole therapy for new patients with Parkinson's disease. Selegiline may be of use for patients with motor fluctuations although it is not necessarily better than alternative strategies such as slow-release levodopa, dopamine agonists or COMT inhibition.