Drug & supplement interaction

Soy + Isocarboxazid

Isocarboxazid brand name: Marplan.

Major Interaction
Medically reviewed by · Updated September 2026
The bottom line Major

Soy has a major interaction with Isocarboxazid. Taking soy products containing high amounts of tyramine along with MAOIs can increase the risk of hypertensive crisis.

Read the full interaction report
SeverityMajor
LikelihoodLikely
EvidenceC
What do Severity, Likelihood & Evidence mean?
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Interaction report

Soy and Isocarboxazid

Here is the interaction we found between these two, with the evidence behind it.

Major

MONOAMINE OXIDASE INHIBITORS (MAOIs)

Why this applies to Isocarboxazid

Isocarboxazid falls under MONOAMINE OXIDASE INHIBITORS (MAOIs) — the group Soy interacts with.

Taking soy products containing high amounts of tyramine along with MAOIs can increase the risk of hypertensive crisis.
Fermented soy products such as tofu and soy sauce contain tyramine, a naturally occurring chemical that affects blood pressure regulation. The metabolism of tyramine is decreased by MAOIs. Consuming more than 6 mg of tyramine while taking an MAOI can increase the risk of hypertensive crisis. The amount of tyramine in fermented soy products is usually less than 0.6 mg per serving; however, there can be significant variation depending on the specific product used, storage conditions, and length of storage. Storing one brand of tofu for a week can increase tyramine content from 0.23 mg to 4.8 mg per serving. Advise patients taking MAOIs to avoid fermented soy products that contain high amounts of tyramine.
Severity Major Likelihood Likely Evidence C

Well-controlled human studies have demonstrated the likely existence of this interaction.

Dr. Brian Staiger, PharmD, BCPS
Dr. Brian Staiger explains PharmD, Clinical Pharmacist

Here's the thing about Isocarboxazid (Marplan): as an MAO inhibitor, it slows down your body's ability to break down a chemical called tyramine. Normally tyramine gets cleared quickly, but on this medication it can build up and shove your blood pressure dangerously high. That's what we call a hypertensive crisis, and it can show up as a pounding headache, racing heart, sweating, neck stiffness, or nausea. It's a true emergency.

Most fresh soy and a single serving of tofu or soy sauce are low in tyramine, but fermented and aged soy products are the worry, and storage can really raise the tyramine amount. Because the risk here is serious, the safest move is to steer clear of fermented soy while you're on Marplan. Please check with your pharmacist or doctor about which soy foods are okay for you.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Shulman KI, Walker SE. Refining the MAOI diet: tyramine content of pizzas and soy products. J Clin Psychiatry 1999;60:191-3. DOI
  2. Gardner DM, Shulman KI, Walker SE, Tailor SA. The making of a user friendly MAOI diet. J Clin Psychiatry 1996;57:99-104.
  3. Walker SE, Shulman KI, Tailor SA, Gardner D. Tyramine content of previously restricted foods in monoamine oxidase inhibitor diets. J Clin Psychopharmacol 1996;16:383-8. PubMed

What These Ratings Mean

Every interaction above is graded three ways — here’s the key to each label.

Severity how clinically significant the interaction is
Major

Clinically significant. Avoid the combination, or use only under close professional supervision.

Moderate

Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.

Minor

Generally not serious. Be aware of it and mention it to your pharmacist.

Likelihood how strong the evidence is that the interaction actually happens in people
  • LikelyWell-controlled human studies have demonstrated the likely existence of this interaction.
  • ProbableInteraction has not been documented in well-controlled studies, however, the interaction has been demonstrated in some small human studies or in controlled animal studies in conjunction with multiple case reports.
  • PossibleInteraction has been documented in animal or in lab research, or the interaction has been documented in humans but is limited to case reports or conflicting clinical research exists.
  • UnlikelyInteraction has been demonstrated in animal or in lab research but has been shown not to occur in humans.
Evidence the quality of the studies behind the rating (graded A–D)
  • AHigh-quality meta-analysis (quantitative systematic review).
  • BCase-control study.
  • CConsensus.
  • DAnecdotal evidence.

These ratings are for information only. Never start, stop, or otherwise change your therapy before speaking with your provider.

Keep it in perspective

Soy Also Interacts With Other Medications

Soy has 8 major, 343 moderate, 259 minor known drug interactions in our database — the Isocarboxazid one above is one of them. If you take anything else, check it against the full list below.

Major 8 Moderate 343 Minor 259 No known interaction 2,220 (incl. Isocarboxazid)
Taking anything else?

Check Another of Your Medications Against Soy

Covers the 2,830 medications we’ve checked against Soy. Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Isocarboxazid

This page covers Soy only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Isocarboxazid page lists 81 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Beer (major), Bitter Orange (major), Brewer's Yeast (major) and Cowhage (major).

By severity: 14 major · 55 moderate · 12 minor.

From our pharmacist’s overview on the Isocarboxazid page

“Isocarboxazid (Marplan) is an MAOI antidepressant, and that drug class carries some of the sharpest supplement and food hazards in the pharmacy, so read this list closely rather than skimming it. Fourteen of the 81 entries rate major, and most of the danger runs through tyramine.”

Reviewed by 2 · Jul 18, 2026

Open the Isocarboxazid interaction page

One more smart check

Taking Soy as Part of a Dietary Supplement Product? Check It for Interactions

We hold 821 real supplement products containing Soy, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Soy. Your product may carry other ingredients that interact with Isocarboxazid too, on top of Soy — and those would not show on this page. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Soy and Isocarboxazid Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Soy
Top 25%

#224 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Isocarboxazid
Steady interest

#2,535 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Supplement

About Soy

What is Soy?

  • Menopause symptoms (hot flashes)
  • Heart and cholesterol health
  • Bone health
  • Plant-based protein source
  • General nutrition

Soy is a nutritious bean that is a staple food and a popular source of plant protein and isoflavones. Eating soy foods as part of a balanced diet is generally considered safe for most people, and there is moderate evidence it may modestly help cholesterol and some menopause symptoms, though results vary. Talk with your pharmacist or doctor before using concentrated soy isoflavone supplements, especially if you have a history of hormone-sensitive conditions.

Read the full Soy monograph & all interactions
Medication

About Isocarboxazid

What Is Isocarboxazid Used For?

Brand name: Marplan

Marplan (isocarboxazid) is indicated for the treatment of depression — specifically, major depressive disorder. Because it carries serious risks, it is not a first-choice antidepressant. Marplan is generally reserved for patients who have not responded adequately to other antidepressants.

Clinical trials showed Marplan to be effective in adult outpatients with major depressive disorder, including those whose depression was accompanied by anxiety symptoms such as panic or phobias. Marplan is not approved for use in children or adolescents.

See full Isocarboxazid drug information
Keep checking

Other Drugs & Soy

Browse every other medication we’ve checked against Soy — both the ones with a known interaction and the ones without. Select any drug for the full detail.

8Major
343Moderate
259Minor
2,219No known interaction
8 Major 343 Moderate 259 Minor 2,219 No interaction
Major

8 interactions

Moderate

343 interactions

Showing 60 of 343 moderate interactions — see all 343 on the Soy page.

Minor

259 interactions

Showing 60 of 259 minor interactions — see all 259 on the Soy page.

No interaction 2,219 drugs checked — show the list

We also checked Soy against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,219 medications checked with no known interaction — see the full Soy list.

See the full Soy interactions page
See every supplement checked against Isocarboxazid, ranked by severity
Sources

Sources & How We Checked

Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

Keep exploring
Soy monograph › Uses, safety, and every drug interaction in one place Isocarboxazid supplement interactions › Every supplement checked against Isocarboxazid, ranked by severity Isocarboxazid drug information › The full plain-English guide to this medication Supplement interaction checker › Check any supplement or product against your medications Browse medications A–Z › Every drug we've checked against herbs & supplements Ask a pharmacist › Free, personal answer from our licensed team
Pharmacist Counseling Corner

Taking Soy and Isocarboxazid Together: Common Questions

Can you take Soy with Isocarboxazid?
This is rated a major interaction, so the combination is best avoided unless your doctor or pharmacist has specifically told you otherwise. Read the full details on this page and confirm with your pharmacist before combining them.
How serious is the Soy and Isocarboxazid interaction?
We rate it Major. This is a clinically significant combination that is generally best avoided, or used only under the direct supervision of your physician or pharmacist.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Still Have a Question About Isocarboxazid and Soy?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.