Dr. Jenni Jacobsen, PhD
Author: Dr. Jenni Jacobsen, PhD Medical Reviewer: Morgan Blair Last updated:

Isocarboxazid is an antidepressant drug used to treat people who do not experience adequate symptom relief with other types of antidepressant medication. While it can be effective in the treatment of depression, isocarboxazid is not the first choice for treating this mental health condition, because of safety concerns, side effects, and dietary restrictions that come along with it [1] [2].

Isocarboxazid brand names

In the United States, isocarboxazid is most commonly marketed under the brand name Marplan [1].

What is isocarboxazid prescribed for?

Isocarboxazid is an antidepressant drug, but it can be prescribed for multiple psychiatric conditions. It is used to treat not only major depressive disorder, but also dysthymia (persistent depression), panic disorder, and phobias [3]. Given the safety concerns associated with this medication, it is not a first line of treatment for any mental health disorder. Rather, it is prescribed in patients who do not respond to other medications [2].

How does isocarboxazid work?

Isocarboxazid belongs to a class of drugs called monoamine oxidase inhibitors (MAOI). As the name suggests, this drug class works by blocking activity of the monoamine oxidase enzyme, which is responsible for breaking down numerous neurotransmitters, including dopamine, tyramine, serotonin, and norepinephrine [2].

By blocking the activity of the monoamine oxidase enzyme, isocarboxazid stops the breakdown of these neurotransmitters, and increases their availability in the nervous system. This allows the neurotransmitters to act upon the cells that are affected by depression and related psychiatric disorders [2].

How is isocarboxazid usually taken?

Isocarboxazid comes in tablet form and is taken by mouth, usually between two and four times per day. The medication is available as a 10 mg tablet. It’s important to take this medication exactly as prescribed. Your doctor and pharmacist will be able to tell you how often to take isocarboxazid [1] [3].  

How long does isocarboxazid stay in your system?

Isocarboxazid is rapidly metabolized by the liver. The medication has a half-life of 1.5 to 4 hours, which is the amount of time it takes half of the original dose of the drug to leave the system. Most of a drug is eliminated from the body after 4 to 5 half-lives, meaning that it takes 6 to 20 hours for isocarboxazid to leave the system [3] [4].

Isocarboxazid side effects

Isocarboxazid, like any medication, comes with side effects. If your doctor has prescribed this medication, they have determined that the benefits of the medication outweigh the potential risk of adverse effects. However, if side effects are severe and interfere with daily life, it’s important to discuss them with your doctor.

Common side effects of isocarboxazid include [1]:

  • Dryness in the mouth
  • Constipation
  • Diarrhea
  • Weakness
  • Severe fatigue
  • Forgetfulness
  • Reduced sexual performance
  • Difficulty or pain during urination
  • Urinating more frequently than usual

The side effects above are often considered mild, and they may improve with time. More severe side effects associated with isocarboxazid include:

  • Headache
  • Racing heart or chest pain
  • Fever or sweating
  • Chills
  • Cold, clammy skin
  • Dizziness
  • Feelings of tightness in the chest or throat
  • Neckstiffness or pain
  • Nausea and/or vomiting
  • Fainting
  • Blurred vision
  • Sensitivity to light
  • Increased pupil size
  • Yellowing in the skin or eyes
  • Uncontrollable shaking in any part of the body
  • Sudden jerking movements
  • Seizures
  • Numbness or tingling in the limbs

If you experience severe side effects, contact your doctor immediately, or present to an emergency room for immediate medical care.

Isocarboxazid precautions

In addition to being mindful of potential side effects, it’s essential to be aware of the following safety precautions that apply when taking isocarboxazid [1]:

  • You must tell your doctor about all other medications and supplements you’re taking, as some of them may interact with isocarboxazid.
  • This medication can make you very drowsy, and you shouldn’t drive, operate heavy machinery, climb, or fly a plane until you confirm how significantly isocarboxazid affects you.
  • You’ll likely need to get out of bed slowly while taking isocarboxazid, because the medication can cause dizziness and fainting, especially when you get up quickly.
  • If you’re pregnant or plan to become pregnant, it’s important to discuss this with your doctor before taking isocarboxazid.
  • Before having any surgery, including dental surgery, it’s important to tell the surgeon that you’re taking isocarboxazid.
  • If you’re taking medication for nausea or diabetes, it’s essential that you tell your doctor before beginning isocarboxazid, as the dosages of your other medications may need to be changed.
  • Monoamine oxidase inhibitors like isocarboxazid can cause liver injury in rare cases. If you have a history of liver disease, it’s important to discuss this with your doctor before beginning this medication [5].

Isocarboxazid interactions

There are various substances and medications that can cause potentially dangerous interactions when taken in combination with isocarboxazid, which is why it’s essential to tell your doctor about all substances and medications you’re using. The following substances are known to cause potential interactions with isocarboxazid, but there are additional medications that could also be problematic [1] [2] [6]:

  • Other antidepressant drugs: Taking isocarboxazid in combination with other antidepressant drugs, such as selective serotoninreuptake inhibitors (SSRIs) like Prozac or Zoloft, can cause serotonin syndrome, which is potentially fatal. Symptoms include fever, sweating, confusion, seizures, fluctuations in heart rhythm and blood pressure, and organ problems. Given this risk, isocarboxazid should not be taken alongside other antidepressants.
  • Tyramine-containing foods: Dietary restrictions required when taking isocarboxazid can be significant, because this medication can interact with tyramine-containing foods, causing an increase in blood pressure that can lead to hemorrhage. Tyramine levels increase as foods age, which means that patients taking isocarboxazid should avoid leftovers and choose fresh foods. Other tyramine-containing foods that can cause dangerous interactions include sausage, turkey, liver, salami, cheeses, fava beans, and overripe fruits, such as bananas, avocados, raisins, and figs.
  • Alcohol: Alcohol can increase the drowsiness caused by isocarboxazid and should not be consumed while taking this medication.
  • Opioids: Opioid drugs like Tramadol and Demerol can also increase ther isk of serotonin syndrome and should not be taken with isocarboxazid.
  • Bupropion: Bupropion, the substance in brand name drugs including Wellbutrin and Zyban, should not be taken with isocarboxazid.
  • Buspirone: When used with buspirone, a medication for the treatment of anxiety, isocarboxazid can cause dangerously elevated blood pressure.
  • Stimulant Drugs: Stimulant medications, including ADHD drugs such as Ritalin and Adderall, can cause hypertension and other severe adverse reactionsin combination with isocarboxazid.
  • Drugs used in the treatment of Parkinson disease:Medications, including Levodopa, which are used to treat symptoms of Parkinson disease, can cause hypertension, headaches, and other serious side effects when used with isocarboxazid.
  • Cough medication: The cough medication dextromethorphan should not be used with isocarboxazid, as the interaction of these two medications can lead to bizarre or psychotic behavior.
  • Antihypertensive drugs: Isocarboxazid should not be used with antihypertensive drugs, which are used to treat high blood pressure, as thesedrug interactions can cause dangerously low blood pressure.
  • CNS Depressants: Any medication or substance that depresses, or slows, the activity of the central nervous system (CNS) has the potential to cause dangerous interactions with isocarboxazid. Some of these substances have been mentioned elsewhere, but some CNS depressants that can be harmful include alcohol, narcotic drugs, and barbiturates.

The list above is not exhaustive and does not include every specific medication that can interact with isocarboxazid, so you must consult with a doctor about the potential interaction between isocarboxazid and any medications you’re taking.

Isocarboxazid storage

Isocarboxazid should be stored at room temperature. It should not be kept in a bathroom, since it should be away from excess heat and moisture. Keep the medication in its original container, out of reach of children. Keeping isocarboxazid in a pill container or in other locations where children can reach it could result in unintentional poisoning [1].

What to do if you overdose on isocarboxazid

Isocarboxazid can result in overdose. Symptoms of overdose include elevated heart rate, dizziness, fainting, blurred vision, seizures, slowed breathing or reflexes, fever, sweating, nausea, and coma [1].

If you or someone you know shows signs of isocarboxazid overdose, contact poison control immediately. If a person has collapsed, is non-responsive, has a seizure, or has trouble breathing, call 911 or take them to the emergency room immediately [1].

  1. National Library of Medicine. (2016). Retrieved August 9, 2023, from
  2. Sub Labah, T., & Saadabadi, A. (2022). Monoamine oxidase inhibitors (MAOI). National Library of Medicine. Retrieved August 9, 2023, from
  3. DrugBank Online. (2021). Isocarboxazid. Retrieved August 9, 2023, from
  4. Hallare, J., & Gerriets, V. (2023). Half life.National Library of Medicine. Retrieved August 10, 2023 from,is%20removed%20from%20the%20body.
  5. National Institute of Diabetes and Digestive and Kidney Diseases. (2012). LiverTox: Clinical and research information on drug-induced liver injury. National Library of Medicine. Retrieved August 10, 2023 from
  6. Validus Pharmaceuticals. (2007). FDA. Retrieved August 10, 2023 from
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Dr. Jenni Jacobsen, PhD
Author Dr. Jenni Jacobsen, PhD Medical Reviewer, Writer

Dr. Jenni Jacobsen, PhD is a medical reviewer, licensed social worker, and behavioral health consultant, holding a PhD in clinical psychology.

Published: Oct 6th 2023, Last edited: Nov 10th 2023

Morgan Blair
Medical Reviewer Morgan Blair MA, LPCC

Morgan Blair is a licensed therapist, writer and medical reviewer, holding a master’s degree in clinical mental health counseling from Northwestern University.

Content reviewed by a medical professional. Last reviewed: Oct 6th 2023