Marplan (Isocarboxazid) for Depression

Marplan (isocarboxazid) is a prescription medication approved by the U.S. Food and Drug Administration (FDA) for treating depression in adults.

How Marplan Works and How It’s Taken

Marplan is a type of medication called a monoamine oxidase (MAO) inhibitor that works by blocking monoamine oxidase, an enzyme found in the brain and other parts of the body. This may raise levels of certain brain chemicals, and that may help improve symptoms of depression, although its exact antidepressant effect is not fully understood.

Doctors prescribe Marplan to adults with depression, including major depressive episodes.

Marplan is given as a tablet by mouth, typically in divided doses two to four times a day. Treatment usually starts with a lower daily dose, and a doctor may raise it gradually based on how well it is tolerated.

Typical Dosing for Depression

The recommended starting dose of Marplan for depression is one 10-milligram tablet twice daily.

A doctor may increase the dose every two to four days to reach 40 milligrams a day by the end of the first week, then by up to 20 milligrams a week if needed and tolerated, to a maximum of 60 milligrams a day. After the best response is reached, a doctor may slowly lower the dose over several weeks.

If there is no response after three to six weeks, a doctor may decide continued treatment is unlikely to help.

This information is based on the prescribing information, but your healthcare provider may tailor your treatment plan. Always follow their guidance.

Marplan Side Effects

In clinical studies of Marplan for depression in adults, the most common side effects that occurred more often than placebo (an inactive treatment) were:

Dizziness
Dry mouth
Nausea

Serious Side Effects and Warnings

Marplan can cause serious side effects that require immediate medical attention. These include:

Suicidal thoughts and behaviors — Risk may be higher in individuals ages 18 to 24, especially early in treatment or when the dose changes.
Hypertensive crisis — Dangerously high blood pressure can cause severe headache, heart pounding, chest or throat tightness, sweating, neck stiffness, nausea or vomiting, and bleeding in the brain.
Hypotension (low blood pressure) — This can include orthostatic hypotension, a drop in blood pressure when standing that can cause dizziness or fainting.
Hepatotoxicity (liver injury) — This can include jaundice, or yellowing of the skin or eyes.
Seizures — Marplan may lower the seizure threshold.

Get medical help right away if you think you are having a serious reaction.

Additional warnings for Marplan include:

Serotonin syndrome — This serious reaction is caused by excessive serotonin accumulation in the body and may occur if Marplan is used with certain drugs or foods. Tell your doctor about all medications you use, and your doctor should ask about your diet.
Activation of mania or hypomania — Very high energy, fast talking, or unusual behavior may occur if Marplan is used in individuals with bipolar disorder. Your doctor should ensure that you don’t have bipolar disorder.

What To Know Before Taking Marplan

Tell your doctor if you have any allergies to isocarboxazid. Do not take Marplan if you have a known hypersensitivity to isocarboxazid.

Tell your doctor about all medicines you take, including prescription drugs, over-the-counter medicines, and supplements.

Do not take Marplan if you have:

A confirmed or suspected cerebrovascular defect, or problem with the blood vessels in your brain
Cardiovascular disease
High blood pressure
A history of headache
Pheochromocytoma, a tumor that can affect hormone levels and blood pressure
A history of liver disease or abnormal liver function tests
Severe kidney impairment

Do not take Marplan with certain other medicines or foods. These include other MAO inhibitors, dibenzazepine-related medicines, stimulants like amphetamines, and some medicines that slow the brain, such as narcotics and alcohol.

Do not take it with some blood pressure medicines, diuretics, antihistamines, sedatives, or anesthetic drugs. It should also not be used with bupropion, buspirone, or dextromethorphan.

Avoid foods high in tyramine, such as aged cheeses, and limit caffeine. Do not use over-the-counter cold, allergy, or weight-loss products that contain vasoconstrictors.

If you are pregnant, planning to become pregnant, or breastfeeding while taking Marplan, talk with your doctor about the risks and benefits. It is not known if Marplan can cause fetal harm.

If you become pregnant during treatment with Marplan, talk with your doctor about registering with the National Pregnancy Registry for Antidepressants by calling 866-961-2388.

Community FAQs

These answers are fact-checked by our editorial staff.

How effective is Marplan?

In two studies that lasted six weeks, adults with depression who took Marplan had more improvement in their symptoms than those who took a placebo. Doctors measured this using a standard test called the Hamilton Depression Scale, which tracks how severe depression symptoms are.

How long does Marplan take to work for depression?

Some individuals may not feel better right away when taking Marplan. It can take three to six weeks to see improvement. If there is no improvement after that time, the doctor may decide the treatment is unlikely to help.

Can Marplan be used with other medicines for depression?

Marplan should not be taken with, or in close proximity to, certain other medicines for depression. These include SSRIs, bupropion hydrochloride, buspirone hydrochloride, other MAO inhibitors, and dibenzazepine-related medicines.

Serious and sometimes fatal reactions can happen with these combinations. Marplan’s effects can continue after stopping the medicine.

Your doctor may have you wait 10 days, two weeks, or five weeks before starting another medicine, depending on which medicine is being used.

What tests or monitoring are needed with Marplan for depression?

Individuals taking Marplan should be watched closely, especially in the first few months and when the dose changes. Doctors should look for worsening depression, suicidal thoughts, or unusual behavior.

Blood pressure should be checked regularly because a dangerous rise in blood pressure can happen. Blood tests to check liver function should also be done during treatment.

The medicine should be stopped if there are signs of liver problems or jaundice.