1. What It Is

Selegiline is a medication primarily used as an adjunct treatment in Parkinson's disease and as a treatment for depression, particularly in its transdermal form. It is a selective monoamine oxidase B (MAO-B) inhibitor, which helps increase dopamine levels in the brain, thus addressing the dopamine deficiency commonly seen in Parkinson's disease. Selegiline also has applications in managing major depressive disorder and other neurodegenerative conditions due to its neuroprotective effects.

2. Dosage Forms and Strengths

Selegiline is available in various dosage forms to accommodate different medical needs:

• Oral Tablets: 5 mg
• Oral Capsules: 5 mg and 10 mg
• Transdermal Patch: 6 mg/24 hours, 9 mg/24 hours, and 12 mg/24 hours
• Oral Disintegrating Tablets: 1.25 mg The form prescribed depends on the specific condition being treated, whether Parkinson's disease or depression.

3. Brand and Generic Names

• Generic Name: Selegiline
• Brand Names:
  • Eldepryl (for Parkinson’s disease in oral form)
  • Zelapar (oral disintegrating form for Parkinson’s)
  • Emsam (transdermal patch for depression)

4. Indications for Use

• Parkinson’s Disease: Selegiline is used as an adjunct to levodopa/carbidopa therapy to manage symptoms and improve motor function by preventing the breakdown of dopamine in the brain.
• Major Depressive Disorder (MDD): The transdermal patch form (Emsam) is prescribed for the treatment of MDD, particularly for patients who have not responded to other antidepressants.
• Other Indications: There is ongoing research on Selegiline's potential role in treating Alzheimer's disease, cognitive decline, and other neurodegenerative disorders.

5. Mechanism of Action

Selegiline works by selectively inhibiting monoamine oxidase B (MAO-B), an enzyme that breaks down dopamine in the brain. By inhibiting this enzyme, Selegiline increases dopamine levels, which are often reduced in Parkinson’s disease. In depression, the transdermal form bypasses the gut and can inhibit both MAO-A and MAO-B at higher doses, increasing the availability of serotonin, norepinephrine, and dopamine, which are involved in mood regulation.

6. Administration and Dosage

• Parkinson’s Disease:
  • Oral Tablets/Capsules: Typically, 5 mg is given twice a day, either with breakfast and lunch.
  • Oral Disintegrating Tablet: 1.25 mg daily before breakfast.
• Major Depressive Disorder:
  • Transdermal Patch: The patch is applied once daily to dry, intact skin. The initial dose is usually 6 mg/24 hours, with adjustments up to 12 mg/24 hours if necessary.

The transdermal patch offers flexibility by reducing dietary restrictions associated with MAO inhibitors, as it delivers Selegiline directly into the bloodstream, minimizing gastrointestinal side effects.

7. Side Effects and Precautions

• Common Side Effects:

  • Nausea
  • Dizziness
  • Insomnia
  • Headache
  • Orthostatic hypotension (low blood pressure upon standing)
  • Dry mouth

• Serious Side Effects:

  • Hypertensive crisis (particularly when interacting with tyramine-rich foods or certain drugs in oral forms)
  • Serotonin syndrome when combined with other serotonergic drugs
  • Hallucinations and confusion, particularly in elderly patients

• Precautions:

  • Dietary Restrictions: Oral Selegiline requires patients to avoid foods high in tyramine (aged cheeses, cured meats, fermented foods), as MAO inhibition can lead to a hypertensive crisis.
  • Drug Interactions: Selegiline should not be used with other MAO inhibitors, SSRIs, SNRIs, or certain pain medications like meperidine, due to the risk of serotonin syndrome or hypertensive crises.
  • Monitoring: Patients on higher doses or transdermal patches should be monitored for blood pressure and mental status, especially in older adults.

8. Conclusion

Selegiline is a valuable therapeutic agent in managing Parkinson’s disease and depression due to its ability to increase dopamine availability. Its selective inhibition of MAO-B makes it effective in alleviating symptoms of dopamine deficiency in Parkinson’s disease while offering an alternative treatment for depression through its transdermal application. However, caution is necessary when prescribing Selegiline due to potential side effects, dietary restrictions, and drug interactions, especially in oral formulations. Regular monitoring and patient education are essential to ensure safe and effective use.