What is Selegiline used for?

Introduction to Selegiline

Selegiline, also known under the trade names Eldepryl, Zelapar, and Emsam, is a medication primarily used for the treatment of Parkinson's disease and major depressive disorder. Developed in the 1960s, Selegiline has undergone extensive research to understand its mechanisms, efficacy, and potential new therapeutic applications. Initially developed by Hungarian chemist József Knoll, Selegiline was introduced to the market as an adjunct to levodopa/carbidopa therapy in Parkinson's disease. The drug falls under the category of monoamine oxidase inhibitors (MAOIs), specifically a selective inhibitor of monoamine oxidase B (MAO-B). This selectivity has provided a more favorable side effect profile compared to earlier MAOIs, making it a valuable tool in treatment regimens.

In addition to its primary indications, there is ongoing research into its potential benefits for other neurological conditions such as Alzheimer's disease and treatment-resistant depression. Various research institutions continue to investigate Selegiline's broader applications and potential neuroprotective effects.

Selegiline Mechanism of Action

Selegiline's primary mechanism of action involves the selective inhibition of monoamine oxidase B (MAO-B), an enzyme responsible for the breakdown of dopamine in the brain. By inhibiting MAO-B, Selegiline increases the levels of dopamine, which helps to alleviate symptoms of Parkinson's disease characterized by dopamine deficiency. This increase in dopamine can lead to improved motor function and a reduction in symptoms such as tremors, stiffness, and bradykinesia (slowness of movement).

Besides its role in inhibiting MAO-B, Selegiline has been shown to have some neuroprotective properties. It can mitigate oxidative stress and protect neurons from apoptosis, making it a subject of interest for diseases characterized by neuronal degeneration. The drug also exhibits secondary mechanisms including the inhibition of the uptake of dopamine and other monoamines, contributing to its antidepressant effects.

How to Use Selegiline

Selegiline is available in various forms, including oral tablets, orally disintegrating tablets, and transdermal patches, each with specific methods of administration.

For Parkinson's disease, the typical oral dosage starts at 5 mg taken twice daily, usually at breakfast and lunch to avoid insomnia, a potential side effect. The orally disintegrating tablets (Zelapar) are taken once daily, usually in the morning, and should be allowed to dissolve on the tongue without chewing or swallowing whole. The transdermal patch (Emsam), used primarily for major depressive disorder, is applied to the skin once daily and delivers the drug through the skin into the bloodstream, providing a steady dose over 24 hours.

The onset of action for Selegiline varies based on the form in which it is administered. Oral forms may start showing effects within a few days to weeks, while the transdermal patch may take up to several weeks for noticeable improvement in depressive symptoms. Regardless of the form, it’s crucial to follow the prescribed dosage and administration guidelines to avoid potential side effects and maximize therapeutic benefits.

What are Selegiline Side Effects

Like all medications, Selegiline can cause side effects, some of which may be serious. Common side effects include nausea, dizziness, dry mouth, and insomnia. These are generally mild and can often be managed with supportive care or by adjusting the dosage. However, more severe side effects can occur and may require immediate medical attention. These include severe headache, hallucinations, arrhythmias, and significant increases in blood pressure.

One of the primary contraindications for Selegiline is the concurrent use of other MAO inhibitors or drugs that can interact with monoamine oxidase, such as certain antidepressants (SSRIs, SNRIs), opioids (like meperidine), and sympathomimetic drugs. The combination of these medications with Selegiline can lead to serious conditions like serotonin syndrome or hypertensive crisis.

Because Selegiline is a selective MAO-B inhibitor at lower doses, it typically does not require dietary restrictions. However, at higher doses, it can lose its selectivity, inhibiting both MAO-A and MAO-B. This lack of selectivity raises the risk of hypertensive crisis if tyramine-rich foods (such as aged cheeses, cured meats, and fermented products) are consumed. Therefore, it is vital to adhere to dietary guidelines if on a high dose or if advised by a healthcare provider.

What Other Drugs Will Affect Selegiline

Several drugs can interact with Selegiline, altering its efficacy or increasing the risk of adverse effects. Antidepressants, particularly SSRIs, SNRIs, and tricyclic antidepressants, can interact dangerously with Selegiline, leading to serotonin syndrome. This condition is characterized by symptoms such as agitation, hallucinations, rapid heart rate, and increased body temperature, and it can be life-threatening if not treated promptly.

Opioid pain medications such as meperidine, tramadol, and methadone should be avoided when taking Selegiline due to the risk of severe interactions, including serotonin syndrome and respiratory depression. Other substances that can interact with Selegiline include sympathomimetic agents like pseudoephedrine and phenylephrine, often found in over-the-counter cold and allergy medications. These combinations can lead to hypertensive crisis, characterized by a sudden, dangerous increase in blood pressure.

Furthermore, certain dietary supplements and herbal products such as St. John's Wort, which is often used for depression, can also interact with Selegiline and should be used with caution or avoided. It is crucial to inform healthcare providers about all the medications, supplements, and herbs one is taking to avoid potential interactions.

In conclusion, Selegiline is a valuable medication for managing Parkinson's disease and major depressive disorder, with ongoing research into its broader applications. Understanding its mechanisms, proper usage, potential side effects, and drug interactions is essential for optimizing its therapeutic benefits while minimizing risks. Always consult healthcare providers for personalized advice and follow prescribed guidelines carefully.