Phenelzine is used to treat depression in people who have not been helped by other medications. Phenelzine is in a class of medications called monoamine oxidase inhibitors (MAOIs). It works by increasing the amounts of certain natural substances that are needed to maintain mental balance.

Side Effects Of Phenelzine

Phenelzine may cause side effects. Tell your doctor if any of the following symptoms are severe or do not go away:

  • drowsiness
  • weakness
  • dizziness
  • dry mouth
  • constipation
  • weight gain
  • decreased sexual ability
  • uncontrollable shaking of any part of the body
  • muscle twitching or jerking

Some side effects can be serious. If you experience any of the following symptoms or those listed in the WARNINGS and PRECAUTIONS section, call your doctor immediately:

  • headache
  • slow, fast, or pounding heartbeat
  • neck stiffness or soreness
  • chest pain
  • nausea
  • vomiting
  • sweating
  • wide pupils (black circles in the middle of the eyes)
  • eyes more sensitive to light than usual
  • swelling of face, throat, arms, hands, feet, ankles, or lower legs
  • difficulty breathing or swallowing
  • yellowing of the skin or eyes

Phenelzine may cause other side effects. Call your doctor if you experience any unusual problems while you are taking this medication.

Warnings & Precautions

Before taking phenelzine:

  • tell your doctor and pharmacist if you are allergic to phenelzine or any other medications.
  • tell your doctor if you are taking, have recently taken, or plan to take any of the following prescription and non-prescription medications: certain other antidepressants including amitriptyline (Elavil), amoxapine, clomipramine (Anafranil), desipramine (Norpramin), doxepin (Sinequan), imipramine (Tofranil), maprotiline, mirtazapine (Remeron), nortriptyline (Pamelor), protriptyline (Vivactil), and trimipramine (Surmontil);amphetamines such as amphetamine (in Adderall), benzphetamine (Didrex), dextroamphetamine (Dexedrine, Dextrostat, in Adderall), and methamphetamine (Desoxyn);bupropion (Wellbutrin, Zyban); buspirone (BuSpar); caffeine (No-Doz, Quick-Pep, Vivarin); cyclobenzaprine (Flexeril); dexfenfluramine (Redux) (not available in the U.S.); dextromethorphan (Robitussin, others); duloxetine (Cymbalta); epinephrine (Epipen, Primatene Mist); guanethidine (Ismelin) (not available in the U.S.); levodopa (Larodopa, in Sinemet); medications for allergies, cough and cold symptoms, hay fever; anxiety, sinus problems, or weight loss (diet pills, appetite suppressants); medications for seizures such as carbamazepine (Tegretol); narcotic medications for pain; nasal decongestants, including nose drops and sprays; other MAOIs such as isocarboxazid (Marplan); pargyline (not available in the U.S.), procarbazine (Matulane), tranylcypromine (Parnate), and selegiline (Eldepryl, Emsam, Zelapar); meperidine (Demerol); methyldopa (Aldomet); ‘pep pills’; sedatives; selective serotonin reuptake inhibitors such as citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac), fluvoxamine (Luvox), paroxetine (Paxil), and sertraline (Zoloft);sleeping pills; tranquilizers; venlafaxine (Effexor); and medications containing alcohol (Nyquil, elixirs, others). Your doctor may tell you not to take phenelzine if you are taking or have recently stopped taking one or more of these medications.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, and herbal products you are taking or plan to take. Be sure to mention any of the following: barbiturates such as pentobarbital (Nembutal), phenobarbital (Luminal), and secobarbital (Seconal); beta-blockers such as atenolol (Tenormin), labetalol (Normodyne), metoprolol (Lopressor, Toprol XL), nadolol (Corgard), and propranolol (Inderal); doxepin cream (Zonelon), insulin and oral medications for diabetes; and medication for high blood pressure including diuretics (‘water pills’), and reserpine (Serpalan). Your doctor may need to change the doses of your medications and monitor you carefully for side effects.
  • you should know that phenelzine may remain in your body for several weeks after you stop taking the medication. During the first few weeks after your treatment ends, tell your doctor and pharmacist that you have recently stopped taking phenelzine before you start taking any new medications.
  • tell your doctor if you are taking any nutritional supplements, especially phenylalanine (DLPA)(contained in aspartame-sweetened products such as diet sodas and foods, over-the-counter medications, and some prescription medications), rauwolfia, tyrosine, or tryptophan.
  • tell your doctor if you have or have ever had pheochromocytoma (a tumor on a small gland near the kidneys) or heart or liver disease. Your doctor may tell you not to take phenelzine.
  • tell your doctor if you use street drugs. Also, tell your doctor if you have or have ever had high blood pressure; diabetes; seizures; schizophrenia (a mental illness that causes disturbed thinking, loss of interest in life, and strong or unusual emotions); agitation; or hyperactivity or other movement disorders.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking phenelzine, call your doctor.
  • if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking phenelzine.
  • you should know that this medication may make you drowsy. Do not drive a car or operate machinery until you know how this medication affects you.
  • do not drink alcohol while you are taking phenelzine. Alcohol can make the side effects of phenelzine worse.
  • you should know that phenelzine may cause dizziness, lightheadedness, and fainting when you get up too quickly from a lying position. This is more common when you first start taking phenelzine. To avoid this problem, get out of bed slowly, resting your feet on the floor for a few minutes before standing up.

Phenelzine Dosage

Phenelzine comes as a tablet to take by mouth. It is usually taken three times a day,. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take phenelzine exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Your doctor will probably start you on a low dose of phenelzine and gradually increase your dose. After your symptoms have improved, your doctor will probably gradually decrease your dose. Follow these directions carefully.

Phenelzine controls the symptoms of depression but does not cure the condition. It may take 4 weeks or longer for you to feel the full benefit of phenelzine. Continue to take phenelzine even if you feel well. Do not stop taking phenelzine without talking to your doctor. Your doctor probably will want to decrease your dose gradually. If you suddenly stop taking phenelzine, you may experience withdrawal symptoms such as nightmares, agitation, loss of contact with reality, nausea, vomiting, and weakness.


Keep all appointments with your doctor and the laboratory. Your doctor will check your blood pressure regularly during your treatment with phenelzine.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.


All information has been provided courtesy of MedLinePlus from the National Library of Medicine and from the FDA.