8 mins read

Uses

What is phenelzine used for?

Phenelzine is commonly used to treat certain types of depression.

Phenelzine may also be used for other conditions as determined by your healthcare provider.

How does phenelzine work (mechanism of action)?

Phenelzine belongs to a group of medicines called monoamine oxidase inhibitors (MAOIs). It is believed to increase the amount of natural chemicals called norepinephrine, dopamine, and serotonin in the brain.

How is phenelzine supplied (dosage forms)?

Brands and other names

  • Nardil

Dosage forms and strengths 

  • 15 mg oral tablets 

How should I store phenelzine?

Phenelzine should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place. Store in a tightly closed container. Protect from light.

Side Effects

What are the most common side effects of phenelzine?

The most common side effects of phenelzine are listed below. Tell your healthcare provider if you have any of these side effects that bother you.

  • Dizziness
  • Headache
  • Sleep problems, including drowsiness or trouble sleeping
  • Feeling unusually tired or weak
  • Unwanted movements, including twitching or trembling
  • Digestive tract problems, including constipation
  • Dry mouth
  • Weight gain
  • Low blood pressure upon standing (see below)
  • Fluid retention
  • Sexual problems, including impotence or difficulty reaching orgasm

There may be other side effects of phenelzine that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of phenelzine?

While less common, the most serious side effects of phenelzine are described below, along with what to do if they happen.

Severe Allergic Reactions. Phenelzine may cause allergic reactions, which can be serious. Stop taking phenelzine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Suicidal Thoughts or Actions. Phenelzine or other antidepressants may increase the risk of suicidal thoughts or actions in a small number of children, teenagers, or young adults in the first few months of taking the medicine or when the dose is changed. Depression or other serious mental health conditions are the most important causes of suicidal thoughts or actions. If you or your child is about to harm themselves, call 911 or call or text 988, the Suicide & Crisis Lifeline. Call your healthcare provider right away if you have any of the following symptoms.

  • New or increased thoughts of suicide or death
  • Suicide attempt
  • New or increased feelings of anxiety, depression, or other unusual changes in your mood or behavior

Extremely Elevated Mood (Mania). People with bipolar disorder can have severe high and low moods. The first symptom of bipolar disorder may be depression. People with bipolar disorder who are treated with an antidepressant, such as phenelzine, may have a higher risk of having mania or a manic episode. Call your doctor right away if you have any of the following symptoms of a manic episode.

  • Very increased energy
  • Significant trouble sleeping
  • Racing, fast-paced thoughts
  • Reckless behavior
  • Unusually grand ideas
  • Excessive happiness or irritability
  • Talking faster or more than normal

Increased Blood Pressure (Hypertension). Phenelzine may increase your blood pressure or make it worse if you have a history of high blood pressure. Call your healthcare provider if your blood pressure increases while taking this medicine.

If you measure your blood pressure and the top number (systolic) is 180 mm Hg or higher or the bottom number (diastolic) is 120 mm Hg or higher, get medical attention right away. Increases in blood pressure may not be noticeable but look out for any of the following symptoms of severely high blood pressure.

  • Sudden severe headache
  • Chest pain
  • Dizziness or confusion
  • Trouble breathing
  • Nausea/vomiting
  • Blurry or other changes to vision
  • Anxiety
  • Buzzing in the ears
  • Nosebleed
  • Feeling of skipped heartbeats

Low Blood Pressure Upon Standing (Orthostatic Hypotension). Phenelzine may cause a sudden drop in blood pressure when standing up from a seated or lying position. This may also cause fainting. To help prevent this, be careful not to get up too quickly. If you feel dizzy, sit or lie down right away until the dizziness stops, then take your time getting up again. Tell your healthcare provider right away if you have any of the following symptoms of orthostatic hypotension.

  • Dizziness, feeling lightheaded, or fainting upon standing
  • Blurred vision
  • Confusion
  • Feeling weak

Serotonin Syndrome. Serotonin syndrome is when there is too much of a chemical called serotonin in your body. Phenelzine can cause serotonin syndrome when it is used with other medicines that affect serotonin. This condition can be life-threatening. Get emergency help if you have any of the following symptoms of serotonin syndrome.

  • Sweating, fever, or flushing
  • Confusion
  • Feeling agitated or restless
  • Seeing or hearing unusual things
  • Dizziness
  • Fast or racing heartbeat
  • Nausea, vomiting, or diarrhea
  • Muscle twitching, stiffness, or tremor
  • Seizures

Warnings & Precautions

Who should not use phenelzine?

Allergies to Ingredients. People who are allergic to any of the following should not take phenelzine.

  • Phenelzine
  • Nardil
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific phenelzine products they stock.

Drug Interactions. Phenelzine should not be taken while you are using certain other medicines. Before taking phenelzine, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Adrenal Gland Tumor (Pheochromocytoma). Phenelzine should not be taken if you have a rare adrenal gland tumor known as pheochromocytoma.

Congestive Heart Failure. Phenelzine should not be taken if you have congestive heart failure.

Kidney Problems. Phenelzine should not be taken if your kidneys are not working as well as they should be. If there is a concern about the health of your kidneys, your healthcare provider may do tests to determine if they are working well enough to take this medicine.

Liver Problems. Phenelzine should not be used if your liver is not working as well as it should be. If there is a concern about the health of your liver, your healthcare provider may do tests to determine if it is working well enough to take this medicine.

Food Interactions. Phenelzine should not be taken together with certain types of food that contain high amounts of a natural compound called tyramine. These foods should be avoided while taking phenelzine. See the Interactions section for more details.

Surgeries Requiring General or Local Anesthesia. Medicines used for general anesthesia and certain types of local anesthesia can increase the risk of dangerous side effects of phenelzine. Phenelzine should not be used prior to elective surgeries that require this type of anesthesia. Tell your healthcare provider if you plan to undergo any elective surgeries or dental procedures while taking phenelzine.

What should I know about phenelzine before using it?

Do not take phenelzine unless it has been prescribed to you by a healthcare provider. Take it as prescribed.

Do not share phenelzine with other people, even if they have the same condition as you. It may harm them.

Keep phenelzine out of the reach of children.

Do not stop taking phenelzine without talking to your healthcare provider. Stopping too quickly may cause certain side effects. Call your healthcare provider right away if you have any new side effects after stopping phenelzine, such as the following.

  • Vivid nightmares
  • Agitation
  • Psychosis
  • Seizures

Phenelzine may cause you to feel sleepy. Phenelzine may also cause dizziness, especially when you stand up quickly after lying or sitting down. Do not drive or do other activities that require alertness or coordination until you know how phenelzine affects you.

What should I tell my healthcare provider before using phenelzine?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if phenelzine is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your healthcare provider if you have any of the following.

  • High or low blood pressure
  • Personal or family history of bipolar disorder or mania
  • Schizophrenia
  • Liver or kidney problems
  • Diabetes
  • Seizures

Pregnancy. It is not known if or how phenelzine could affect pregnancy or harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant.

Breastfeeding. It is not known if phenelzine passes into breast milk. It is not known if phenelzine can be safely used while you are breastfeeding. Tell your healthcare provider if you are breastfeeding or plan to breastfeed.

Interactions

Does phenelzine interact with foods or drinks?

Phenelzine can increase your body’s sensitivity to tyramine, a natural compound found in large amounts in foods such as aged cheese, cured or processed meat, pickled or fermented vegetables, citrus and tropical fruits, and fermented alcoholic beverages such as beer or red wine. Avoid eating foods high in tyramine as well as excessive amounts of chocolate and caffeine while taking phenelzine and for at least 2 weeks after stopping phenelzine, as this may increase the risk of large increases in your blood pressure.

Do not drink alcohol while taking phenelzine. You could have very serious side effects if you drink alcohol while taking this medicine.

Does phenelzine interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking phenelzine.

  • Amphetamines or methylphenidate, which are medicines commonly used to treat ADHD
  • An selective serotonin reuptake inhibitor (SSRI) or a serotonin norepinephrine reuptake inhibitor (SNRI) within the past 2 weeks (5 weeks if the medicine was fluoxetine), which is a medicine that is commonly used for depression
  • A tricyclic antidepressant, such as imipramine, amitriptyline, nortriptyline, or protriptyline, even if it is not used for depression
  • Another monoamine oxidase inhibitor (MAOI), such as selegiline or rasagiline, within the past 2 weeks, which is a medicine usually used for depression or Parkinson’s disease
  • Epinephrine, such as Epipen, which is a medicine used for severe allergic reactions 
  • Methyldopa, which is a medicine used to reduce blood pressure
  • Levodopa, which is a medicine for Parkinson’s disease
  • A decongestant such as phenylephrine, which is used to treat nasal congestion caused by cold or allergies
  • Dextromethorphan, which is a cough suppressant contained in many prescription and OTC products for cold and flu symptoms
  • An opioid, such as meperidine, which is used for certain types of pain
  • Buspirone, which is a medicine commonly used for anxiety
  • Tryptophan or tyrosine, which are supplements that may be used to help the body make proteins and certain brain-signaling chemicals
  • Bupropion, which is a medicine commonly used for depression 
  • Cyclobenzaprine, which is a muscle relaxant
  • Carbamazepine (Tegretol, Carbatrol, and others), which is a medicine commonly used to treat seizures or nerve pain
  • Products that contain caffeine, which is often found in medicines for reducing water weight (diuretics), staying awake, headaches, and hangover relief
  • Any other medicine that causes dizziness and sleepiness, such as prescription pain medicines, sleep medicines, and medicines for anxiety

This may not be a complete list of medicines that can interact with phenelzine. Always check with your healthcare provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much phenelzine?

If you or someone else has used too much phenelzine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of phenelzine?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.