Medically reviewed by Drugs.com. Last updated on Apr 25, 2022.
Antidepressants increased the risk compared to placebo of suicidal thinking and behavior (suicidality) in children, adolescents, and young adults in short-term studies of major depressive disorder (MDD) and other psychiatric disorders. Anyone considering the use of phenelzine sulfate or any other antidepressant in a child, adolescent, or young adult must balance this risk with the clinical need. Short-term studies did not show an increase in the risk of suicidality with antidepressants compared to placebo in adults beyond age 24; there was a reduction in risk with antidepressants compared to placebo in adults aged 65 and older. Depression and certain other psychiatric disorders are themselves associated with increases in the risk of suicide. Patients of all ages who are started on antidepressant therapy should be monitored appropriately and observed closely for clinical worsening, suicidality, or unusual changes in behavior. Families and caregivers should be advised of the need for close observation and communication with the prescriber. Phenelzine sulfate is not approved for use in pediatric patients .
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
Therapeutic Class: Antidepressant
Pharmacologic Class: Monoamine Oxidase Inhibitor, Nonselective
Uses for phenelzine
Phenelzine is used to treat certain types of depression. It belongs to the group of medicines called monoamine oxidase inhibitors (MAOI). Phenelzine works by blocking the action of a chemical substance known as monoamine oxidase (MAO) in the nervous system.
Although phenelzine is very effective for certain patients, it may also cause some unwanted reactions if taken the wrong way. It is very important to avoid certain foods, beverages, and medicines while you are using phenelzine. Your doctor may provide a list as a reminder of which products you should avoid.
Phenelzine is available only with your doctor's prescription.
Before using phenelzine
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For phenelzine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to phenelzine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Appropriate studies have not been performed on the relationship of age to the effects of phenelzine in the pediatric population. Safety and efficacy have not been established.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of phenelzine in the elderly. However, elderly patients are more likely to have age-related kidney, liver, or heart problems, which may require caution and an adjustment in the dose for patients receiving phenelzine.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking phenelzine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using phenelzine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
- Methylene Blue
Using phenelzine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
- Iobenguane I 123
- Iobenguane I 131
- Ma Huang
- Morphine Sulfate Liposome
- St John's Wort
Using phenelzine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
- Insulin Aspart, Recombinant
- Insulin Bovine
- Insulin Degludec
- Insulin Detemir
- Insulin Glargine, Recombinant
- Insulin Glulisine
- Insulin Lispro, Recombinant
Interactions with food/tobacco/alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using phenelzine with any of the following is not recommended. Your doctor may decide not to treat you with this medication, change some of the other medicines you take, or give you special instructions about the use of food, alcohol, or tobacco.
- Dopamine Containing Food
- Tyramine Containing Food
Using phenelzine with any of the following is usually not recommended, but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use phenelzine, or give you special instructions about the use of food, alcohol, or tobacco.
- Bitter Orange
Other medical problems
The presence of other medical problems may affect the use of phenelzine. Make sure you tell your doctor if you have any other medical problems, especially:
- Bipolar disorder (manic-depressive illness) or
- Congestive heart failure or
- Kidney disease, severe or
- Liver disease, history of or
- Pheochromocytoma (an adrenal problem)—Should not be used in patients with these conditions.
- Diabetes or
- Hypotension (low blood pressure) or
- Schizophrenia—Use with caution. May make these conditions worse.
Proper use of phenelzine
Take phenelzine exactly as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered. To do so may increase the chance of side effects.
Phenelzine should come with a medication guide. Read and follow these instructions carefully. Ask your doctor if you have any questions.
The dose of phenelzine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of phenelzine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For oral dosage form (tablets):
- For depression:
- Adults—At first, 15 milligrams (mg) three times a day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 90 mg per day.
- Children—Use is not recommended.
- For depression:
If you miss a dose of phenelzine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Precautions while using phenelzine
It is very important that your doctor check your progress at regular visits to allow for changes in your dose and to check for any unwanted effects.
You will also need to have your blood pressure measured before starting phenelzine and while you are using it. If you notice any change to your recommended blood pressure, call your doctor right away. If you have questions about this, talk to your doctor.
When taken with certain foods, drinks, or other medicines, phenelzine can cause very dangerous reactions, such as sudden high blood pressure (also called hypertensive crisis). To avoid such reactions, follow these rules of caution:
- Do not eat foods that have dopamine and a high tyramine content (most common in foods that are aged or fermented to increase their flavor), such as cheese (especially strong or aged kinds), caviar, sour cream, liver, canned figs, soy sauce, sauerkraut, fava beans, yeasts, and yogurt. Avoid smoked or pickled meat, poultry, or fish, such as sausage, pepperoni, salami, anchovies, or herring. Do not eat dried fruit (such as raisins), bananas, avocados, raspberries, or very ripe fruit.
- Do not drink alcoholic beverages. This includes Chianti wine, sherry, beer, non-alcohol or low alcohol beer and wine, and liqueurs.
- Do not eat or drink too much caffeine. Caffeine can be found in coffee, cola, chocolate, tea, and many other foods and drinks. Ask your doctor how much caffeine is safe to use.
Phenelzine may cause some people to be agitated, irritable, or display other abnormal behaviors. It may also cause some people to have suicidal thoughts and tendencies or to become more depressed. If you or your caregiver notice any of these adverse effects, tell your doctor right away.
Call your doctor or hospital emergency room right away if you have a severe headache, stiff or sore neck, chest pains, fast heartbeat, sweating, dizziness, or nausea and vomiting while you are taking phenelzine. These may be symptoms of a serious side effect called hypertensive crisis.
Phenelzine may cause blurred vision or make some people drowsy or less alert than they are normally. Make sure you know how you react to phenelzine before you drive, use machines, or do anything else that could be dangerous if you are unable to see well or not alert.
Phenelzine will add to the effects of alcohol and other CNS depressants (medicines that slow down the nervous system, possibly causing drowsiness). Some examples of CNS depressants are antihistamines or medicine for hay fever, allergies, or colds; sedatives, tranquilizers, or sleeping medicine; prescription pain medicine or narcotics; medicine for seizures or barbiturates; muscle relaxants; or anesthetics, including some dental anesthetics. Check with your doctor before taking any of the above while you are using phenelzine.
Dizziness, lightheadedness, or fainting may occur, especially when you get up suddenly from a lying or sitting position. Getting up slowly may help. When you get up from lying down, sit on the edge of the bed with your feet dangling for 1 or 2 minutes, then stand up slowly. If the problem continues or gets worse, check with your doctor.
Do not stop taking phenelzine without checking first with your doctor. Your doctor may want you to gradually reduce the amount you are using before stopping it completely.
Before having any kind of surgery, dental treatment, or emergency treatment, tell the medical doctor or dentist in charge that you are using phenelzine or have used it within the past 10 days. Taking phenelzine together with medicines that are used during surgery, dental, or emergency treatments may increase the risk of serious side effects.
Your doctor may want you to carry an identification card stating that you are using phenelzine.
Phenelzine may affect blood sugar levels. If you are diabetic, be especially careful in testing for sugar in your blood or urine. If you have any questions about this, check with your doctor.
After you stop using phenelzine, you must continue to exercise caution for at least 2 weeks with your foods, drinks, and other medicines, since these items may continue to react with phenelzine.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.
Phenelzine side effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
- cold sweats
- dizziness, faintness, or lightheadedness when getting up from a lying or sitting position
- overactive reflexes
- shakiness in the legs, arms, hands, or feet
- sudden jerky movements of the body
- trembling or shaking of the hands or feet
- Abdominal or stomach pain
- actions that are out of control
- burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
- change in consciousness
- clay-colored stools
- dark urine
- decrease in frequency of urination
- decrease in urine volume
- difficult or troubled breathing
- difficulty in passing urine (dribbling)
- disorganized thoughts
- false or unusual sense of well-being
- fast, pounding, or irregular heartbeat or pulse
- fear or nervousness
- general feeling of discomfort, illness, or weakness
- high blood pressure
- increased sweating
- irregular, fast or slow, or shallow breathing
- lack of emotion or feelings
- loss of appetite
- loss of consciousness
- loud or fast speech
- low blood pressure
- muscle tremors
- muscle twitching
- nausea or vomiting
- no emotion or expression in speech
- painful urination
- pale or blue lips, fingernails, or skin
- rapid, deep, or shallow breathing
- seeing or hearing things that are not there
- shakiness and unsteady walk
- shortness of breath
- slow or irregular heartbeat
- stomach cramps
- swelling of the feet or lower legs
- talking, feeling, and acting with excitement
- uncontrolled eye movements
- unpleasant breath odor
- unsteadiness, trembling, or other problems with muscle control or coordination
- unusual paleness
- unusual tiredness or weakness
- vomiting of blood
- yellow eyes or skin
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- decreased interest in sexual intercourse
- dry mouth
- inability to have or keep an erection
- loss in sexual ability, desire, drive, or performance
- loss of appetite
- not able to have an orgasm
- passing of gas
- stomach pain, fullness, or discomfort
- trouble sleeping
- unable to sleep
- unusually deep sleep
- unusually long duration of sleep
- weight gain
- blurred vision
- decreased vision
- eye pain
- redness, swelling, or soreness of the tongue
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
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