See also How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with selegiline include: antidepressants (including bupropion, maprotiline, mirtazapine), other MAO inhibitors (isocarboxazid, linezolid, metaxalone, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, safinamide, tranylcypromine), appetite suppressants (such as diethylpropion), drugs for attention deficit disorder (such as atomoxetine, methylphenidate), apraclonidine, buspirone, carbamazepine/oxcarbazepine, cyclobenzaprine, deutetrabenazine, certain herbal products (such as ephedra/ma huang), cold medications/nasal decongestants (such as phenylephrine, phenylpropanolamine, pseudoephedrine), fentanyl, metoclopramide, street drugs (such as LSD, mescaline), stimulants (such as amphetamines, ephedrine), supplements (such as tryptophan, tyramine), tetrabenazine, certain "triptans" used to treat migraine headaches (such as rizatriptan, sumatriptan, zolmitriptan), valbenazine.

The risk of serotonin syndrome/toxicity increases if you are also taking other drugs that increase serotonin. Examples include street drugs such as MDMA/"ecstasy," St. John's wort, dextromethorphan, certain antidepressants (including SSRIs such as fluoxetine/paroxetine, SNRIs such as duloxetine/venlafaxine, TCAs such as amitriptyline/doxepin), certain opioid medications (such as meperidine, methadone, pentazocine, propoxyphene, tramadol, tapentadol), among others. The risk of serotonin syndrome/toxicity may be more likely when you start or increase the dose of these drugs.

Tell your doctor or pharmacist if you are using any of these medications before, during, or within 2 weeks after treatment with selegiline. Tell your doctor or pharmacist if you have taken fluoxetine during at least 5 weeks before starting selegiline. Discuss with your doctor how much time to wait between starting or stopping any of these drugs and taking selegiline.

Check the labels on all your medicines (such as allergy, cough-and-cold products, diet pills) because they may contain dextromethorphan, decongestants, or stimulants. Ask your pharmacist about the safe use of those products.

This medication may interfere with certain medical/lab tests (such as brain scan for Parkinson's disease), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.