Drug & supplement interaction

Phenethylamine (pea) + Isocarboxazid

Isocarboxazid brand name: Marplan.

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

Isocarboxazid falls into 2 drug categories that Phenethylamine (pea) can interact with; the most serious is rated moderate. Theoretically, combining serotonergic drugs with phenethylamine might increase the risk of serotonergic adverse effects.

Read the full interaction report
SeverityModerate
LikelihoodPossible
Interactions2
EvidenceD
What do Severity, Likelihood & Evidence mean?
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Interaction report

Phenethylamine (pea) and Isocarboxazid

These two interact in 2 distinct ways. Each one is explained separately below.

Why Are There 2 Interactions?

Phenethylamine (pea) interacts with whole categories of medication. Isocarboxazid falls into 2 of those categories, so it can interact with Phenethylamine (pea) in 2 different ways. We’ve listed each one below — your overall risk is driven by the most serious of them (Moderate).

Moderate

SEROTONERGIC DRUGS

1 of 2

Why this applies to Isocarboxazid

Isocarboxazid falls under SEROTONERGIC DRUGS — the group Phenethylamine (pea) interacts with.

Theoretically, combining serotonergic drugs with phenethylamine might increase the risk of serotonergic adverse effects.
Animal research shows that phenethylamine increases levels of serotonin, norepinephrine, and dopamine. Theoretically, combining serotonergic drugs with phenethylamine might increase the risk of additive serotonergic adverse effects, including serotonin syndrome and cerebral vasoconstrictive disorders. However, low-quality clinical research has used phenethylamine with selegiline, a monoamine oxidase inhibitor (MAOI), with apparent safety.
Severity Moderate Likelihood Possible Evidence D

Interaction 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.

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

Here's the thing about isocarboxazid (Marplan): it's a strong MAO inhibitor, which means it blocks the very enzymes (including MAO-B) that normally break down compounds like PEA. So if you took PEA while on Marplan, the PEA wouldn't get cleared the usual way. It could build up and stack on top of an already powerful drug, raising your levels of serotonin, norepinephrine, and dopamine.

In real terms, that could mean a dangerous spike in blood pressure, headache, racing heart, sweating, or agitation, the kind of reaction MAOIs are famous for. The evidence here is mostly theoretical and animal-based, but with a drug as touchy as Marplan, I wouldn't gamble on it. Please check with your pharmacist or doctor before combining them.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Singhal AB, Caviness VS, Begleiter AF, et al. Cerebral vasoconstriction and stroke after use of serotonergic drugs. Neurology 2002;58:130-3. PubMed
  2. Sabelli H, Fink P, Fawcett J, et al. Sustained antidepressant effect of PEA replacement. J Neuropsychiatry Clin Neurosci. 1996;8(2):168-71.
  3. Xie Z, Miller G. Beta-phenylehtylamine alters monoamine transporter function via trace amine-associated receptor 1: implication for modulatory roles of trace amines in brain. J Pharmacol Exp Ther. 2008;325(2):617-28.
  4. Nakamura M, Ishii A, Nakahara D. Characterization of beta-phenyltheylamine-induced monoamine release in rat nucleus accumbens: a microdialysis study. Eur J Pharmacol. 1998;349(2-3):163-9.
  5. Bailey B, Philips S, Boulton A. In vivo release of endogenous dopamine, 5-hydroxytryptamine and some of their metabolites from rat caudate nucleus by phenylethylamine. Neurochem Res. 1987;12(2):173-8. PubMed
Moderate

MONOAMINE OXIDASE INHIBITORS (MAOIs)

2 of 2

Isocarboxazid also falls under MONOAMINE OXIDASE INHIBITORS (MAOIs).

Theoretically, taking phenethylamine concomitantly with MAOIs may increase adverse effects.
In humans, phenethylamine is oxidized by MAO-B to form the inactive metabolite phenylacetic acid. Animal research shows that administering an MAOI prior to phenethylamine increases the amphetamine-like effects of phenethylamine. However, low-quality clinical research has used phenethylamine with selegiline, an MAOI, with apparent safety.
Severity Moderate Likelihood Possible Evidence D

Interaction 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.

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

Here's the thing to understand about Marplan (isocarboxazid): it works by blocking the very enzyme that normally breaks down phenethylamine (PEA). Your body usually clears PEA quickly using MAO-B, but isocarboxazid shuts that pathway down. So if you add a PEA supplement on top, that PEA can pile up instead of being cleared, and its stimulant-like effects can be amplified.

In real terms, that could mean a spike in blood pressure, a racing or pounding heart, headache, sweating, or feeling jittery and anxious. This concern comes mostly from animal studies and is rated as theoretical, so we don't have strong human proof. Still, with an MAOI like this, I'd treat it seriously. Please don't combine them without first checking with your pharmacist or doctor.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. Sabelli H, Fink P, Fawcett J, et al. Sustained antidepressant effect of PEA replacement. J Neuropsychiatry Clin Neurosci. 1996;8(2):168-71.
  2. Mantegazza P, Riva M. Amphetamine-like activity of beta-phenethylamine after a monoamine oxidase inhibitor in vivo. Journal of Pharmacy and Pharmacology. 1963;151(1):472-8.
  3. Grimsby J, Toth M, Chen K, et al. Increased stress response and beta-phenylethylamine in MAOB-deficient mice. Nat Genet. 1997;17(2):206-10.
  4. Lindemann L, Hoener MC. A renaissance in trace amines inspired by a novel GPCR family. Trends Pharmacol Sci. 2005;26(5):274-81. 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

Phenethylamine (pea) Also Interacts With Other Medications

Phenethylamine (pea) has 186 moderate known drug interactions in our database — the Isocarboxazid one above is among them. If you take anything else, check it against the full list below.

Moderate 186 No known interaction 2,644 (incl. Isocarboxazid)
Taking anything else?

Check Another of Your Medications Against Phenethylamine (pea)

Covers the 2,830 medications we’ve checked against Phenethylamine (pea). Pick one to open its full report.

Everything else you take

See Every Supplement That Interacts With Isocarboxazid

This page covers Phenethylamine (pea) 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 Phenethylamine (pea) as Part of a Dietary Supplement Product? Check It for Interactions

We hold 208 real supplement products containing Phenethylamine (pea), each one broken down to its full ingredient list — and combination products often carry several ingredients besides Phenethylamine (pea). Your product may carry other ingredients that interact with Isocarboxazid too, on top of Phenethylamine (pea) — 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 Phenethylamine (pea) 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 Phenethylamine (pea)
Top half

#432 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 Phenethylamine (pea)

What is Phenethylamine (pea)?

Phenethylamine (pea)
  • Mood support
  • Focus and concentration
  • Energy and pre-workout boost
  • Feeling of well-being
  • Athletic performance

Phenethylamine (PEA) is a natural compound made in the body and found in foods like chocolate; supplements are marketed for mood, focus, and energy. Reliable human research on the supplement is very limited, and it may raise blood pressure or heart rate, so people with heart or blood pressure problems should be cautious and check with a pharmacist or doctor first.

Read the full Phenethylamine (pea) 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 & Phenethylamine (pea)

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

0Major
186Moderate
0Minor
2,643No known interaction
186 Moderate 2,643 No interaction
Moderate

186 interactions

Showing 60 of 186 moderate interactions — see all 186 on the Phenethylamine (pea) page.

No interaction 2,643 drugs checked — show the list

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

Showing the 60 most looked-up of 2,643 medications checked with no known interaction — see the full Phenethylamine (pea) list.

See the full Phenethylamine (pea) 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
Phenethylamine (pea) 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 Phenethylamine (pea) and Isocarboxazid Together: Common Questions

Can you take Phenethylamine (pea) with Isocarboxazid?
There is a moderate interaction, so it may be acceptable with monitoring or timing changes — but check with your pharmacist first. Read the full details on this page and confirm with your pharmacist before combining them.
Why are there 2 interactions listed for Phenethylamine (pea) and Isocarboxazid?
Isocarboxazid belongs to more than one drug category, and Phenethylamine (pea) interacts with each of those categories a little differently. We list every one so nothing is missed — your overall risk is driven by the most serious of them.
How serious is the Phenethylamine (pea) and Isocarboxazid interaction?
We rate it Moderate. This combination may require monitoring, a dose adjustment, or separating the times you take each one. Consult your pharmacist before using them together.

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

Still Have a Question About Isocarboxazid and Phenethylamine (pea)?

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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.