Selegiline: Uses, Dosage, Side Effects & Interactions

Selegiline is a medication primarily used in the treatment of Parkinson’s disease and major depressive disorder. It belongs to a class of drugs known as monoamine oxidase inhibitors (MAOIs), specifically targeting the monoamine oxidase B (MAO-B) enzyme. Selegiline helps increase the levels of dopamine, a neurotransmitter involved in movement and mood regulation, in the brain.

Introduction to Selegiline

Selegiline, also known as deprenyl or l-deprenyl, is a selective and irreversible inhibitor of monoamine oxidase B (MAO-B). It is used as an adjunct treatment for Parkinson’s disease and as a monotherapy for major depressive disorder. Selegiline works by inhibiting the breakdown of dopamine, a neurotransmitter that plays a crucial role in movement and mood regulation.

Chemical Properties

Selegiline is a methamphetamine derivative with the chemical formula C ₁₃H ₁₇N. Its structural formula is:
Selegiline Structural Formula”>

The chemical name of selegiline is (-)-(R)-N,α-Dimethyl-N-2-propynylphenethylamine, and it is classified as a selective and irreversible monoamine oxidase B inhibitor. Selegiline exhibits unique pharmacodynamic properties, selectively inhibiting MAO-B while leaving MAO-A mostly unaffected, which reduces the risk of certain side effects associated with non-selective MAO inhibitors.
Source: Progress in Neurobiology, 1996

Mechanism of Action

Selegiline exerts its therapeutic effects by inhibiting the enzyme monoamine oxidase B (MAO-B), which is responsible for the breakdown of dopamine, a neurotransmitter involved in movement and mood regulation. By inhibiting MAO-B, selegiline increases the availability of dopamine in the brain, thereby improving the symptoms of Parkinson’s disease and alleviating depressive symptoms.

The selective inhibition of MAO-B by selegiline is significant because it allows for a safer and more targeted approach compared to non-selective MAO inhibitors, which inhibit both MAO-A and MAO-B enzymes and can lead to more severe side effects and interactions with certain foods and medications.
Source: Brain Research Bulletin, 2001

Clinical Uses

Selegiline has two primary clinical uses:

1. Treatment for Parkinson’s Disease: Selegiline is commonly used as an adjunct treatment in combination with levodopa and carbidopa for the management of Parkinson’s disease. It helps improve motor symptoms such as tremors, stiffness, and difficulty with movement by enhancing the availability of dopamine in the brain.
2. Treatment for Major Depressive Disorder: Selegiline is also approved for the treatment of major depressive disorder, where it is used as a monotherapy. By increasing dopamine and other neurotransmitter levels in the brain, selegiline can alleviate symptoms of depression.

In addition to these primary uses, selegiline has been studied for potential benefits in other neurological and psychiatric conditions, such as Alzheimer’s disease, dementia, and attention deficit hyperactivity disorder ( ADHD).
Source: European Journal of Pharmacology, 2001

Brand Names and Formulations

Selegiline is available under various brand names, including:

• Emsam: A transdermal patch formulation approved for the treatment of major depressive disorder.
• Zelapar: An orally disintegrating tablet formulation used as an adjunct treatment for Parkinson’s disease.
• Generic Versions: Selegiline is also available as generic formulations, including oral tablets and capsules.

Pharmacokinetics

The pharmacokinetic properties of selegiline are as follows:

• Absorption: Selegiline is well-absorbed after oral administration, with a bioavailability of approximately 10% due to extensive first-pass metabolism.
• Metabolism: Selegiline undergoes extensive metabolism in the liver, primarily by the cytochrome P450 enzymes CYP2B6 and CYP2C19. The major metabolites include desmethylselegiline, l-amphetamine, and l-methamphetamine.
• Elimination: Selegiline and its metabolites are primarily eliminated through renal excretion, with a mean elimination half-life of approximately 10 hours.
• Bioavailability: The bioavailability of selegiline varies depending on the formulation. The transdermal patch (Emsam) provides more consistent and sustained delivery compared to oral formulations.

Source: Trends in Pharmacological Sciences, 1999

Dosage and Administration

The recommended dosages for selegiline vary depending on the clinical indication and formulation:

• Parkinson’s Disease: For the adjunct treatment of Parkinson’s disease, the typical starting dose of oral selegiline is 5 mg once daily, which can be gradually increased up to a maximum of 10 mg per day, divided into two doses.
• Major Depressive Disorder: For the treatment of major depressive disorder, the recommended dose of the transdermal Emsam patch is 6 mg/24 hours, applied once daily to the skin.

It is essential to follow the dosage instructions provided by a healthcare professional and adjust the dose based on individual response and tolerability. Selegiline is available in various formulations, including oral tablets, capsules, and transdermal patches.

Side Effects

Common side effects associated with selegiline include:

• Dry mouth
• Dizziness
• Insomnia
• Nausea
• Constipation
• Headache
• Skin irritation (with transdermal patch)

Severe or rare side effects may include confusion, hallucinations, high blood pressure, and interactions with certain medications or foods containing tyramine (a substance found in aged cheeses, fermented foods, and some alcoholic beverages).

Interactions with Other Drugs

Selegiline may interact with various medications, including:

• Other MAO Inhibitors: Concomitant use with other non-selective MAO inhibitors can lead to potentially life-threatening interactions and should be avoided.
• Selective Serotonin Reuptake Inhibitors (SSRIs): Combining selegiline with SSRIs may increase the risk of serotonin syndrome, a potentially dangerous condition.
• Medications Metabolized by CYP2B6 or CYP2C19: Selegiline may affect the metabolism of drugs metabolized by these enzymes, potentially increasing or decreasing their concentrations.

Patients should inform their healthcare providers about all medications they are taking, including over-the-counter drugs, supplements, and herbal products, to avoid potential interactions.

Contraindications

Selegiline is contraindicated in the following situations:

• Concomitant use with other non-selective MAO inhibitors or agents that can potentially cause a hypertensive crisis (e.g., certain decongestants, weight loss medications).
• Known hypersensitivity or allergy to selegiline or any of its components.
• Severe liver or kidney impairment.
• Pheochromocytoma (a rare tumor of the adrenal gland).

Warnings and Precautions

Several warnings and precautions should be considered when using selegiline:

• Patients should avoid consuming foods and beverages high in tyramine, as this can lead to a potentially dangerous increase in blood pressure.
• Selegiline may impair cognitive and motor skills, so caution should be exercised when operating machinery or driving.
• Selegiline may exacerbate symptoms in patients with cardiovascular or cerebrovascular disorders.
• Patients with a history of psychosis or bipolar disorder should be closely monitored, as selegiline may worsen these conditions.

Pharmacology

Selegiline is a selective and irreversible inhibitor of monoamine oxidase B (MAO-B), an enzyme responsible for the breakdown of dopamine, a neurotransmitter involved in movement and mood regulation. By inhibiting MAO-B, selegiline increases the availability of dopamine in the brain, providing symptomatic relief for Parkinson’s disease and alleviating depressive symptoms.

In addition to its symptomatic effects, selegiline has been suggested to possess neuroprotective properties, potentially slowing the progression of neurodegeneration in Parkinson’s disease. However, the exact mechanisms underlying these potential neuroprotective effects are still under investigation.
Source: Neuropharmacology, 2007

History and Development

Selegiline was first synthesized in the 1960s by Hungarian chemists József Knoll and Béla Kučera at the Semmelweis Medical University in Budapest. It was initially developed as a potential treatment for Parkinson’s disease and was approved for this use by the U.S. Food and Drug Administration (FDA) in 1989.

In 2006, a transdermal patch formulation of selegiline (Emsam) was approved by the FDA for the treatment of major depressive disorder, expanding its clinical applications.

Research and Future Directions

Ongoing research is exploring the potential applications of selegiline in various neurological and psychiatric disorders, including:

• Alzheimer’s disease and other forms of dementia
• Attention deficit hyperactivity disorder ( ADHD)
• Traumatic brain injury
• Stroke recovery

Additionally, researchers are investigating the potential neuroprotective mechanisms of selegiline and its ability to slow the progression of neurodegenerative diseases like Parkinson’s.
Source: Neuropharmacology, 2014

Patient Information

Patients taking selegiline should be aware of the following instructions and tips:

• Follow the prescribed dosage and administration instructions carefully.
• Avoid consuming foods and beverages high in tyramine, as they can cause a dangerous increase in blood pressure.
• Manage dry mouth by sucking on sugarless candy, chewing gum, or using saliva substitutes.
• Consult with a healthcare provider before taking any new medications, including over-the-counter drugs and supplements, to avoid interactions.
• Report any severe or persistent side effects to a healthcare professional promptly.

Comparison with Other Treatments

In the treatment of Parkinson’s disease, selegiline is commonly used as an adjunct therapy in combination with levodopa and carbidopa. This combination can provide better symptom control and potentially slow the progression of the disease compared to levodopa alone.

Compared to other MAO inhibitors, selegiline is a selective inhibitor of MAO-B, which reduces the risk of certain side effects associated with non-selective MAO inhibition, such as hypertensive crises and dietary restrictions.

For the treatment of major depressive disorder, selegiline may be considered as an alternative to other antidepressant medications, particularly in cases where traditional treatments have been ineffective or poorly tolerated.

Cultural and Social Impact

Selegiline has played a significant role in improving the quality of life for patients with Parkinson’s disease and major depressive disorder. By alleviating motor symptoms and improving mood, selegiline has helped many individuals maintain their independence and participate more fully in daily activities.

The availability of selegiline has also contributed to a better understanding and acceptance of