Reviewed on 6/29/2022

What Is Isocarboxazid and How Does It Work?

Isocarboxazid is a prescription medication used for the treatment of depression. 

  • Isocarboxazid is available under the following different brand names: Marplan

What Are Side Effects Associated with Using Isocarboxazid?

Common side effects of Isocarboxazid include:

  • headache,
  • dizziness,
  • drowsiness,
  • tremors,
  • sleep problem (insomnia),
  • constipation,
  • nausea, and
  • dry mouth

Serious side effects of Isocarboxazid include:

  • hives,
  • difficulty breathing,
  • swelling of the face, lips, tongue, or throat,
  • mood or behavior changes,
  • anxiety,
  • panic attacks,
  • trouble sleeping,
  • impulsiveness,
  • irritableness,
  • agitation,
  • hostility,
  • aggression,
  • restlessness,
  • hyperactivity (mentally or physically),
  • increase depression,
  • thoughts of self-harm,
  • sudden and severe headache,
  • rapid heartbeat,
  • stiffness in your neck,
  • nausea,
  • vomiting,
  • cold sweat,
  • vision problems,
  • sensitivity to light,
  • chest pain,
  • slow heartbeat,
  • swelling,
  • rapid weight gain,
  • yellow of the skin or eyes (jaundice), and
  • lightheadedness

Rare side effects of Isocarboxazid include:

  • none
  • Seek medical care or call 911 at once if you have the following serious side effects:
  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms such as fast, irregular, or pounding heartbeats; fluttering in your chest; shortness of breath; sudden dizziness, lightheartedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Are Dosages of Isocarboxazid?

Adult dosage


  • 10 mg


Adult and geriatric dosage

  • 10 mg orally every 6-12 hours, increase by 10 mg/day every 2-4 days to 40 mg/day orally divided every 6-12 hours by end of the first week
  • After the first week, may increase by up to 20 mg/week to a maximum of 60 mg/day; decrease dose to maintenance dose once maximum effect achieved

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”.

What Other Drugs Interact with Isocarboxazid?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Isocarboxazid has severe interactions with at least 91 other drugs.
  • Isocarboxazid has serious interactions with at least 106 other drugs.
  • Isocarboxazid has moderate interactions with at least 51 other drugs.
  • Isocarboxazid has minor interactions with the following drugs:

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all your products. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions or concerns.

What Are Warnings and Precautions for Isocarboxazid?


Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Isocarboxazid?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Isocarboxazid?”


  • Use caution with doses above 40 mg/day
  • Clinical worsening & suicide ideation may occur despite medication in adolescents & young adults (18-24 years)
  • Caution in patients with diabetes mellitus (monitor glucose closely), glaucoma, hepatic/renal impairment, thyroid dysfunction
  • Therapy can cause serious side effects; not recommended as initial therapy; should be reserved for patients who have not responded satisfactorily to other antidepressants
  • Hypotension may occur; seen most commonly in patients with preexistent hypertension; blood pressure usually returns rapidly to pretreatment levels upon discontinuation of the drug; dosage increases should be made more gradually in patients showing a tendency toward hypotension at beginning of therapy; postural hypotension may be relieved by having the patient lie down until blood pressure returns to normal
  • Therapy lowers the convulsive threshold in some animal experiments, use caution if epileptic patients are treated; therapy appears to have varying effects in epileptic patients; while some have a decrease in the frequency of seizures, others have more seizures; discontinue at least 48 hours before myelography; should not resume therapy for at least 24 hours postprocedure
  • There is a low incidence of altered liver function or jaundice in patients receiving therapy; periodic liver chemistry tests should be performed during therapy; discontinue use at the first sign of hepatic dysfunction or jaundice
  • MAO inhibitors can suppress anginal pain that would otherwise serve as a warning of myocardial ischemia
  • Use cautiously in hyperactive or agitated patients, as well as in schizophrenic patients; may cause excessive stimulation; activation of mania/hypomania was reported in a small proportion of patients with the major affective disorder who were treated with marketed antidepressants
  • Hypertensive crisis
    • The hypertensive crisis associated with MAO inhibitor use, which can be fatal; may result from co-administration of MAOIs and certain drugs and foods; monitor blood pressure should closely to detect any pressor response; discontinue therapy immediately if palpitations or frequent headaches occur; these symptoms may be prodromal of a hypertensive crisis
    • If a hypertensive crisis occurs, institute therapy to lower blood pressure
  • Bipolar disorder
    • A major depressive episode may be the initial presentation of bipolar disorder; treating such an episode with an antidepressant alone may increase the likelihood of precipitation of a mixed/manic episode in patients at risk for bipolar disorder
    • Before initiating treatment with an antidepressant, patients with depressive symptoms should be adequately screened to determine if they are at risk for bipolar disorder; such screening should include a detailed psychiatric history, including a family history of suicide, bipolar disorder, and depression
    • The drug is not approved for use in treating bipolar depression

Pregnancy and Lactation

  • There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to antidepressants, during pregnancy; healthcare providers are encouraged to register patients by calling the National Pregnancy Registry for Antidepressants at 1-844405-6185 or visiting online at
  • The potential reproductive toxicity of the drug has not been adequately evaluated in animals; it is also not known whether isocarboxazid can cause embryo/fetal harm when administered to a pregnant woman or can affect reproductive capacity; the drug should be given to a pregnant woman only if needed
  • Lactation
    • Levels of excretion in human milk have not been determined, and effects on a nursing infant are unknown; therapy should be used in women who are nursing only if needed

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