isocarboxazid

Adjunctive therapy

Brands: Marplan

Last reviewed 2025-12-30

Reviewed by PsychMed Editorial Team.

View details

Quick answers

What is isocarboxazid?
Isocarboxazid (brand Marplan) is an irreversible, nonselective MAOI antidepressant indicated for major depressive disorder in adults who have not responded to other antidepressants (label).
What is Marplan?
Marplan is a brand name for isocarboxazid.
What is Marplan (isocarboxazid) used for?
Label indications include: Major depressive disorder in adults not responding to other antidepressants (label).
What drug class is Marplan (isocarboxazid)?
Irreversible, nonselective monoamine oxidase inhibitor (MAOI). Generally reserved for treatment-resistant depression because of dietary restrictions and high-risk drug interaction profile (label/clinical).
What strengths does Marplan (isocarboxazid) come in?
Oral tablets (label): 10 mg.

Snapshot

Class: Adjunctive therapy
Common US brands: Marplan
Therapeutic drug monitoring not routinely recommended.
Last reviewed: 2025-12-30

Label indications

Major depressive disorder in adults not responding to other antidepressants (label).

View labelExact

Clinical Highlights

Isocarboxazid (brand Marplan) is an irreversible, nonselective MAOI antidepressant indicated for major depressive disorder in adults who have not responded to other antidepressants (label). MAOIs can be effective for some forms of treatment-resistant depression and atypical depression, but they carry a uniquely high-risk drug and food interaction profile. For many patients, those logistics (and the consequences of mistakes) are the main limiting factor (label/clinical).

Hypertensive crisis can occur with dietary tyramine exposure (aged cheeses, certain cured/fermented foods, some supplements), while serotonin syndrome and other severe reactions can occur with many serotonergic medications (label/clinical).
Irreversible MAO inhibition means interaction risk can persist after stopping. Washout timing is especially important with fluoxetine because of its long half-life (label).
The compare view, isocarboxazid evidence feed, and isocarboxazid print page help frame MAOI-specific safety planning and alternatives.

Dosing & Formulations

Oral tablets (label): 10 mg. Label trials initiated patients at 10 mg twice daily with increases every 2–4 days as tolerated; doses were divided 2–4 times daily up to a labeled maximum of 80 mg/day (label).

Because MAOIs have high-stakes interactions, clinicians often use careful medication reconciliation, written instructions, and clear washout timelines when starting or switching therapy (clinical).

Monitoring & Risks

Boxed warning (antidepressants): increased risk of suicidal thoughts and behaviors in children, adolescents, and young adults; monitor closely early in treatment (class/label). Hypertensive crisis risk with tyramine-containing foods/supplements and sympathomimetic drugs; patient education and emergency planning are core parts of MAOI prescribing (label/clinical).

Serotonin syndrome and severe reactions can occur with serotonergic agents (SSRIs/SNRIs, TCAs, linezolid, methylene blue, some opioids), and with certain combinations even after stopping due to washout needs (label).
Orthostatic hypotension, dizziness, and sleep disruption can occur; these effects can influence fall risk and daytime function (label/clinical).
Teach warning signs that need urgent evaluation (sudden severe headache, chest pain, palpitations, stiff neck, marked confusion), because they can signal hypertensive crisis or other severe reactions (label/clinical).

Drug Interactions

MAOI combinations with SSRIs/SNRIs, many TCAs, stimulants, and other serotonergic/sympathomimetic agents are contraindicated or strongly discouraged because of life-threatening reactions (label). Fluoxetine requires a long washout (weeks) before starting an MAOI due to fluoxetine/norfluoxetine long elimination half-life (label).

OTC decongestants, some weight-loss agents, and certain supplements can raise blood pressure or interact; clinicians often advise avoiding new OTC/supplement starts without review (clinical).

Practice Notes

MAOIs are often positioned after multiple antidepressant trials and augmentation strategies (APA/CANMAT/clinical), and selection usually balances potential benefit against safety logistics. A structured “do-not-combine” list, diet handouts, and an explicit plan for missed doses/symptom escalation can reduce accidental interaction risk (clinical).

References

MARPLAN (isocarboxazid) tablets prescribing information — DailyMed (2023)
Consensus recommendations for MAOI safety and dietary management — Journal of Clinical Psychopharmacology (2022)
APA Clinical Practice Guideline for the Treatment of Depression — American Psychiatric Association (2023)Guidelinedepressionclinical
CANMAT 2024 Clinical Guidelines for Major Depressive Disorder — Canadian Journal of Psychiatry (2024)