Selegiline is a medication classified as a monoamine oxidase inhibitor, or MAOI. It is prescribed for specific neurological and psychiatric conditions and works by influencing the levels of chemical messengers in the brain. The medication is available as an oral capsule, an orally disintegrating tablet, and a transdermal patch. Each form delivers the drug into the body differently, which alters its clinical effects and use.
Medical Uses of Selegiline
Selegiline is primarily used as an adjunctive therapy for Parkinson’s disease, a progressive disorder of the nervous system that impairs movement. It is added to a treatment regimen that includes levodopa and carbidopa, a standard combination therapy for Parkinson’s. When used this way, selegiline can help reduce the required dose of levodopa/carbidopa and smooth out the “wearing-off” periods that patients experience between doses, extending the effectiveness of the primary medication.
The medication also has a distinct application in treating major depressive disorder in adults, where it is administered via a transdermal patch. This delivery method allows the drug to be absorbed directly through the skin into the bloodstream. This alters its pharmacological profile compared to the oral forms used for Parkinson’s.
How Selegiline Works
Selegiline works by inhibiting monoamine oxidase (MAO), an enzyme that breaks down neurotransmitters like dopamine, serotonin, and norepinephrine. There are two types of this enzyme, MAO-A and MAO-B, which are involved in mood and movement control. Selegiline is an irreversible inhibitor, meaning it permanently deactivates the enzyme molecules it binds to.
For Parkinson’s disease, lower doses of selegiline selectively inhibit MAO-B, the enzyme primarily responsible for breaking down dopamine. This action increases dopamine levels in the brain, which can alleviate movement-related symptoms. This selective inhibition is the goal when using the oral forms of the medication.
To treat major depressive disorder, higher concentrations from the transdermal patch cause selegiline to inhibit both MAO-A and MAO-B. The inhibition of MAO-A increases levels of serotonin and norepinephrine, in addition to dopamine. This combined elevation of neurotransmitters is thought to produce its antidepressant effects.
Potential Side Effects
Selegiline can cause a range of side effects. Common effects include dizziness, dry mouth, difficulty sleeping, nausea, and stomach pain. For patients using the transdermal patch, application site reactions such as redness or irritation are also common. Those using the orally disintegrating tablets may experience irritation or sores inside the mouth.
More serious side effects require prompt medical attention. These can include significant changes in mental state, such as confusion or hallucinations, and uncontrolled movements or dyskinesia. Fainting, severe headaches, and a drop in blood pressure upon standing (orthostatic hypotension) are also potential serious effects. Any sudden changes in mood or behavior should be reported to a healthcare provider.
Drug and Food Interactions
A significant concern with selegiline is its interaction with tyramine, an amino acid found in certain foods. When MAO enzymes in the gut are inhibited, the body cannot properly break down tyramine. This can lead to a dangerous spike in blood pressure known as a hypertensive crisis. Patients taking oral selegiline should avoid foods high in tyramine, including:
- Aged cheeses
- Cured meats like salami
- Fermented soy products like tofu
- Certain alcoholic beverages, including some beers and red wines
This dietary restriction is less strict for the low-dose transdermal patch because this form of administration bypasses the gut, reducing the impact on MAO-A there.
Selegiline also has serious interactions with other medications. Combining it with drugs that increase serotonin levels can lead to serotonin syndrome, a life-threatening condition. Medications that must be avoided include:
- Other MAOIs
- Antidepressants like SSRIs (e.g., fluoxetine) and SNRIs
- Triptans used for migraines
- Certain pain relievers such as tramadol and meperidine
Over-the-counter sympathomimetic drugs, found in decongestants containing ephedrine, can also cause a dangerous increase in blood pressure and must be avoided.