Medical Editor: John P. Cunha, DO, FACOEP Last updated on RxList: 10/6/2021
Marplan Side Effects Center

What Is Marplan?

Marplan (isocarboxazid) is a monoamine oxidase inhibitor (MAOI) used to treat symptoms of depression that may include anxiety, panic, or phobias. Marplan is usually given after other antidepressants have been tried without successful treatment of symptoms.

What Are Side Effects of Marplan?

Common side effects of Marplan include:

  • dizziness,
  • headache,
  • drowsiness,
  • tiredness,
  • weakness,
  • problems sleeping,
  • constipation,
  • dry mouth,
  • tremors or shaking, or
  • nausea.

You may have suicidal thoughts when you first start taking an antidepressant such as Marplan, especially if you are younger than 24 years old. Tell your doctor if this occurs. Tell your doctor if you have unlikely but serious side effects of Marplan including:

  • fainting,
  • mental/mood changes (e.g., agitation, confusion),
  • muscle stiffness,
  • changes in sexual ability or interest,
  • shivering,
  • swollen ankles or legs,
  • unusual weight gain, or
  • vision changes (e.g., double or blurred vision).

Dosage for Marplan

Starting dose of Marplan is one tablet (10 mg) twice daily. If tolerated, dosage may be increased by increments of 10 mg every 2 to 4 days to achieve a dosage of four tablets daily (40 mg) by the end of the first week of treatment. Dosage can then be increased to a maximum recommended dosage of 60 mg/day.

What Drugs, Substances, or Supplements Interact with Marplan?

Many other medicines can cause serious or life-threatening medical problems if taken together with Marplan. Do not take Marplan before telling your doctor about all prescription and over-the-counter medications and supplements you use.

Marplan During Pregnancy or Breastfeeding

Marplan should be used only when prescribed during pregnancy. It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Additional Information

Our Marplan (isocarboxazid) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Depression is a(n) __________ . See Answer
Marplan Consumer Information

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Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Report any new or worsening symptoms to your doctor, such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), more depressed, or have thoughts about suicide or hurting yourself.

Stop taking this medicine and call your doctor at once if you have:

  • sudden and severe headache, rapid heartbeat, stiffness in your neck, nausea, vomiting, cold sweat, vision problems, sensitivity to light;
  • chest pain, fast or slow heart rate;
  • swelling, rapid weight gain;
  • jaundice (yellowing of the skin or eyes); or
  • a light-headed feeling, like you might pass out.

Common side effects may include:

  • headache, dizziness, drowsiness;
  • tremors;
  • sleep problems (insomnia);
  • constipation, nausea; or
  • dry mouth.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Marplan (Isocarboxazid)


Learn to Spot Depression: Symptoms, Warning Signs, Medication See Slideshow
Marplan Professional Information


Adverse Findings Observed In Short-Term, Placebo-Controlled Trials

Systematically collected data are available from only 86 patients exposed to Marplan, of whom only 52 received doses of ≥50 mg/day, including only 11 who were dosed at ≥60 mg/day. Because of the limited experience with systematically monitored patients receiving Marplan at the higher end of the currently recommended dose range of up to 60 mg/day, caution is indicated in patients for whom a dose of 40 mg/day is exceeded (see WARNINGS).

The table that follows enumerates the incidence, rounded to the nearest percent, of treatment emergent adverse events that occurred among 86 depressed patients who received Marplan at doses ranging from 20 to 80 mg/day in placebo-controlled trials of 6 weeks in duration. Events included are those occurring in 1% or more of patients treated with Marplan and for which the incidence in patients treated with Marplan was greater than the incidence in placebo-treated patients.

The prescriber should be aware that these figures cannot be used to predict the incidence of adverse events in the course of usual medical practice where patient characteristics and other factors differ from those which prevailed in clinical trials. Similarly, the cited frequencies cannot be compared with figures obtained from other clinical investigations involving different treatments, uses, and investigators. The cited figures, however, do provide the prescribing physician with some basis for estimating the relative contribution of drug and non-drug factors to the adverse event incidence rate in the population studied.

The commonly observed adverse event that occurred in Marplan patients with an incidence of 5% or greater and at least twice the incidence in placebo patients were nausea, dry mouth, and dizziness (see Table).

In three clinical trials for which the data were pooled, 4 of 85 (5%) patients who received placebo, 10 of 86 (12%) who received <50 mg of Marplan per day, and 1 of 52 (2%) who received ≥50 mg of Marplan per day prematurely discontinued treatment. The most common reasons for discontinuation were dizziness, orthostatic hypotension, syncope, and dry mouth.

Treatment-Emergent Adverse Events Incidence in Placebo-Controlled Clinical Trials with Marplan Doses of 40 to 80 mg/day1

MARPLAN <50 mg
MARPLAN ≥50 mg
Drowsy 0 4% 0%
Anxiety 1 2% 0%
Chills 0% 2% 0%
Forgetful 1% 2% 2%
Hyperactive 0% 2% 0%
Lethargy 0% 2% 2%
Sedation 1% 2% 0%
Syncope 0% 2% 0%
Sweating 0% 2% 2%
Heavy feeling 0% 2% 0%
Orthostatic hypotension 1% 4% 4%
Palpitations 1% 2% 0%
Dry mouth 4% 9% 6%
Constipation 6% 7% 4%
Nausea 2% 6% 4%
Diarrhea 1% 2% 0%
Impotence 0% 2% 0%
Urinary frequency 1% 2% 0%
Urinary hesitancy 0% 1% 4%
Headache 13% 15% 6%
Insomnia 4% 4% 6%
Sleep disturbance 0% 5% 2%
Tremor 0% 4% 4%
Myoclonic jerks 0% 2% 0%
Paresthesia 1% 2% 0%
Dizziness 14% 29% 15%
1Events reported by at least 1% of patients treated with Marplan are presented, except for those that had an incidence on placebo greater than or equal to that on Marplan.
2All patients also received Marplan at doses < 50 mg.

Other Events Observed During The Postmarketing Evaluation Of Marplan

Isolated cases of akathisia, ataxia, black tongue, coma, dysuria, euphoria, hematologic changes, incontinence, neuritis, photosensitivity, sexual disturbances, spider telangiectases, and urinary retention have been reported. These side effects sometimes necessitate discontinuation of therapy. In rare instances, hallucinations have been reported with high dosages, but they have disappeared upon reduction of dosage or discontinuation of therapy. Toxic amblyopia was reported in one psychiatric patient who had received isocarboxazid for about a year; no causal relationship to isocarboxazid was established. Impaired water excretion compatible with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) has been reported.

Drug Abuse And Dependence

Controlled Substance Class

Marplan is not a controlled substance.

Physical And Psychological Dependence

Marplan has not been systematically studied in animals or humans for its potential for abuse, tolerance, or physical dependence. There have been reports of drug dependency in patients using doses of Marplan significantly in excess of the therapeutic range. Some of these patients had a history of previous substance abuse. The following withdrawal symptoms have been reported: restlessness, anxiety, depression, confusion, hallucinations, headache, weakness, and diarrhea. Consequently, physicians should carefully evaluate Marplan patients for history of drug abuse and follow such patients closely, observing them for signs of misuse or abuse (eg, development of tolerance, incrementations of dose, drug-seeking behavior).

Read the entire FDA prescribing information for Marplan (Isocarboxazid)

© Marplan Patient Information is supplied by Cerner Multum, Inc. and Marplan Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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