This medication is used to treat depression. Phenelzine belongs to a class of drugs known as monoamine oxidase inhibitors (MAO inhibitors). It works by helping to restore the balance of certain natural substances in the brain.

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This medication may also be used for anxiety and social anxiety disorder (social phobia).

Read the Medication Guide available from your pharmacist before you start using phenelzine and each time you get a refill. If you have any questions, consult your doctor or pharmacist.

Take this medication by mouth with or without food as directed by your doctor, usually 1 to 3 times a day. The dosage is based on your medical condition and response to treatment.

To reduce your risk of side effects, your doctor may start you at a low dose and gradually increase your dose. Once your condition improves and you are better for a while, your doctor may work with you to reduce your regular dose. Follow your doctor's instructions carefully. Do not take more or less medication or take it more often than prescribed. Your condition will not improve any faster and your risk of side effects will increase.

Use this medication regularly in order to get the most benefit from it. To help you remember, use it at the same time(s) each day. It may take several weeks for the full benefits of this medication to be noticed. Do not stop taking this medication without consulting your doctor.

If you suddenly stop using this medication, you may have withdrawal symptoms (such as restlessness, confusion, hallucinations, headache, weakness, and diarrhea). To help prevent withdrawal, your doctor may lower your dose slowly. Withdrawal is more likely if you have used phenelzine for a long time or in high doses. Tell your doctor or pharmacist right away if you have withdrawal.

Tell your doctor if your condition lasts or gets worse.

See also Warning section.

Dizziness, drowsiness, tiredness, weakness, problems sleeping, constipation, and dry mouth may occur. If any of these effects last or get worse, notify your doctor or pharmacist promptly.

To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• fainting
• mental/mood changes (such as agitation, confusion)
• muscle stiffness
• changes in sexual ability/interest
• shaking (tremor)
• shivering
• swollen ankles/legs
• unusual weight gain
• eye pain/swelling/redness
• vision changes (such as double/blurred vision)
• signs of liver problems (such as nausea/vomiting that doesn't stop, stomach/abdominal pain, yellowing eyes/skin, dark urine)
• seizures

This drug may rarely cause an attack of extremely high blood pressure (hypertensive crisis), which may be fatal. Many drug and food interactions can increase this risk (See also Drug Interaction section.) Stop taking phenelzine and get medical help right away if any of these serious side effects occur:

• frequent/severe headache
• fast/slow/irregular/pounding heartbeat
• chest pain
• neck stiffness/soreness
• severe nausea/vomiting
• sweating/clammy skin (sometimes with fever)
• widened pupils
• sudden sensitivity to light (photophobia)

This medication may increase serotonin and rarely cause a very serious condition called serotonin syndrome/toxicity. The risk increases if you are also taking other drugs that increase serotonin, so tell your doctor or pharmacist of all the drugs you take (see Drug Interactions section). Get medical help right away if you develop some of the following symptoms:

• fast heartbeat
• hallucinations
• loss of coordination
• severe dizziness
• severe nausea/vomiting/diarrhea
• twitching muscles
• unexplained fever
• unusual agitation/restlessness

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking phenelzine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• a certain adrenal gland tumor (pheochromocytoma)
• cerebrovascular disease (such as stroke)
• heart problems (such as heart failure, heart attack, coronary artery disease)
• high blood pressure
• history of severe/frequent headaches
• liver problems
• kidney disease
• personal/family history of mental/mood disorders (such as schizophrenia, bipolar disorder)
• diabetes
• certain nervous system diseases (Parkinson's syndrome, seizures)
• overactive thyroid (hyperthyroidism)
• personal/family history of glaucoma (angle-closure type)

This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery or any procedures requiring use of contrast dye (such as myelography), tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). You may need to stop taking this drug beforehand. Follow your doctor's instructions carefully.

If you have heart disease, this medication may mask chest pain. Avoid strenuous exercise while taking this medication.

If you have diabetes, phenelzine may lower your blood sugar. Check your blood sugar regularly as directed and share the results with your doctor. Tell your doctor right away if you have symptoms of low blood sugar such as sudden sweating, shaking, fast heartbeat, hunger, blurred vision, dizziness, or tingling hands/feet. Your doctor may need to adjust your diabetes medication, exercise program, or diet.

Older adults may be more sensitive to the side effects of this drug, especially the effects on blood pressure.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

Since untreated mental/mood problems (such as depression) can be a serious condition, do not stop taking this medication unless directed by your doctor. If you are planning pregnancy, become pregnant, or think you may be pregnant, immediately discuss with your doctor the benefits and risks of using this medication during pregnancy.

It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

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 this drug include:

• other antidepressants (including maprotiline, mirtazapine, nefazodone, TCAs such as amitriptyline/nortriptyline)
• appetite suppressants (such as diethylpropion)
• drugs for attention deficit disorder (such as atomoxetine, methylphenidate)
• apraclonidine
• bupropion
• buspirone
• carbamazepine
• cyclobenzaprine
• deutetrabenazine
• dextromethorphan
• certain drugs for high blood pressure (such as guanethidine, methyldopa, beta blockers such as atenolol, clonidine, rauwolfia alkaloids)
• other MAO inhibitors (isocarboxazid, linezolid, metaxalone, methylene blue, moclobemide, procarbazine, rasagiline, safinamide, selegiline, tranylcypromine)
• metoclopramide
• certain opioid medications (such as fentanyl, meperidine, methadone, tapentadol)
• certain drugs for Parkinson's (such as entacapone, levodopa, tolcapone)
• street drugs (such as LSD, mescaline)
• stimulants (such as amphetamines, cocaine, dopamine, epinephrine, phenylalanine)
• tetrabenazine
• "triptan" migraine drugs (such as sumatriptan, rizatriptan)
• tramadol
• tyrosine
• tryptophan
• 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, certain antidepressants (including SSRIs such as fluoxetine/paroxetine, SNRIs such as duloxetine/venlafaxine), 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 phenelzine. Tell your doctor or pharmacist if you have taken fluoxetine during at least 5 weeks before starting phenelzine. Discuss with your doctor how much time to wait between starting or stopping any of these drugs and taking phenelzine.

Tell your doctor or pharmacist if you are taking other products that cause drowsiness such as opioid pain or cough relievers (such as codeine, hydrocodone), alcohol, marijuana (cannabis), drugs for sleep or anxiety (such as alprazolam, lorazepam, zolpidem), muscle relaxants (such as carisoprodol, cyclobenzaprine), or antihistamines (such as cetirizine, diphenhydramine).

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

It is very important that you follow special dietary restrictions in order to limit the amount of tyramine in your diet. Avoid drinking large amounts of beverages containing caffeine (coffee, tea, colas) or eating large amounts of chocolate. Caffeine can increase the side effects of this medication. Foods and beverages high in tyramine should be avoided while you are taking this medication and for at least 2 weeks after you stop using this medication.

Foods high in tyramine include: aged cheeses (cheddar, camembert, emmenthaler, brie, stilton blue, gruyere, gouda, brick, bleu, roquefort, boursault, parmesan, romano, provolone, liederdranz, colby, edam), aged/dried/fermented/salted/smoked/pickled/processed meats and fish (includes bacon, summer sausage, liverwurst, hot dogs, corned beef, pepperoni, salami, bologna, ham, mortadella, pickled or dried herring), banana peel, beef/chicken liver (stored, not fresh), bouillon cubes, commercial gravies, concentrated yeast extracts, fava beans, Italian green beans, broad beans, fermented bean curd, homemade yeast-leavened bread, kim chee (Korean fermented cabbage), orange pulp, overripe or spoiled fruits, packaged soups, red wine, sauerkraut, sherry, snow pea pods, sourdough bread, soy sauce, soybeans, soybean paste/miso, tofu, tap beer and ale, vermouth.

Moderate-to-low tyramine content foods include: alcohol-free beer, avocados, bananas, bottled beer and ale, chocolate and products made with chocolate, coffee, cola, cultured dairy products (such as buttermilk, yogurt, sour cream), distilled spirits, eggplant, canned figs, fish roe (caviar), green bean pods, pate, peanuts, port wine, raisins, raspberries, red plums, spinach, tomatoes, white wine.

Tell your doctor or pharmacist right away if you notice symptoms of high blood pressure such as fast/slow heartbeat, vomiting, sweating, headache, chest pain, sudden vision changes, weakness on one side of the body, or trouble speaking.

Contact your healthcare professionals (such as doctor, pharmacist, dietician) for more information, including recommendations for your diet.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669.

Do not share this medication with others.

Lab and/or medical tests (such as blood pressure, liver function) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is within 2 hours of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).