Mechanism of Action
The pharmacological profile of selegiline is based on its ability to selectively block monoamine oxidase type B. Under physiological conditions, this enzyme is primarily responsible for the inactivation of the neurotransmitter dopamine in the central nervous system.
By inhibiting MAO-B, the drug artificially slows down the enzymatic degradation of dopamine. This action takes place directly within the dopaminergic neurons of the substantia nigra. As a result of slowed degradation, the concentration of the neurotransmitter is maintained at a consistently high level, helping to compensate for its deficiency in parkinsonism.
Selegiline's interaction with levodopa is of particular clinical importance. The drug potently potentiates (enhances) the pharmacological effects of levodopa. Due to this synergism, clinicians can adjust the therapeutic regimen and safely reduce the dosage of levodopa by an average of 30% while maintaining necessary control over motor symptoms.
Clinical Application
The strategy for prescribing the drug depends directly on the stage of the pathological process:
- Early Stages: Selegiline demonstrates high efficacy as monotherapy during the initial stages of Parkinson's disease.
- Advanced Stages: Combination therapy is the primary and most justified approach. Co-administration with levodopa achieves optimal symptom control.
Neuroprotective Effect
Modern pharmacology suggests that selegiline has the ability to delay the death of dopaminergic neurons. This neuroprotective potential has a clear pathogenetic rationale.
Normal oxidative metabolism of dopamine is inevitably accompanied by the side production of reactive molecules. By blocking this metabolic pathway, selegiline significantly reduces the generation of free oxygen radicals. Reducing oxidative stress prevents further damage to sensitive cellular structures within nervous tissue.
Adverse Effects
Interference with neurotransmitter balance can be accompanied by several adverse reactions across various body systems:
- Central Nervous System (CNS): Impaired concentration and episodes of confusion may occur.
- Cardiovascular System (CVS): Arterial hypotension is a characteristic finding.
- Gastrointestinal Tract (GIT): Nausea and vomiting are the most frequent manifestations.