Drug & supplement interaction

Guarana + Phenelzine Sulfate

Phenelzine Sulfate brand name: Nardil.

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

Guarana has a moderate interaction with Phenelzine Sulfate. Theoretically, concomitant use might increase the risk of a hypertensive crisis.

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

Guarana and Phenelzine Sulfate

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

Moderate

MONOAMINE OXIDASE INHIBITORS (MAOIs)

Why this applies to Phenelzine Sulfate

Phenelzine Sulfate falls under MONOAMINE OXIDASE INHIBITORS (MAOIs) — the group Guarana interacts with.

Theoretically, concomitant use might increase the risk of a hypertensive crisis.
Guarana contains caffeine. Caffeine has been shown to inhibit MAO-A and -B in laboratory studies. Concomitant intake of large amounts of caffeine with MAOIs might precipitate a hypertensive crisis. In a case report, a patient that consumed 10-12 cups of caffeinated coffee and took the MAOI tranylcypromine presented with severe hypertension. Hypertension was resolved after the patient switched to drinking decaffeinated coffee.
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 deal with pairing guarana and phenelzine (Nardil). Guarana is basically a concentrated source of caffeine, and Nardil is an MAOI, a powerful older antidepressant. The worry is that loading up on caffeine while taking an MAOI could push your blood pressure too high. That can show up as a pounding headache, a racing or thumping heartbeat, sweating, or feeling flushed and jittery. In rare cases blood pressure can spike dangerously, which is why this matters.

To be fair, this concern is mostly theoretical and built around one case report involving heavy coffee drinking (10 to 12 cups a day). A normal cup probably isn't the same as a strong guarana energy supplement. Since Nardil already comes with strict diet and stimulant cautions, please check with your pharmacist or doctor before using guarana.

Contact Dr. Brian directly if you have additional questions on this interaction
References
  1. McEvoy GK, ed. AHFS Drug Information. Bethesda, MD: American Society of Health-System Pharmacists, 1998.
  2. MacKenzie, T., Comi, R., Sluss, P., Keisari, R., Manwar, S., Kim, J., Larson, R., and Baron, J. A. Metabolic and hormonal effects of caffeine: randomized, double-blind, placebo-controlled crossover trial. Metabolism 2007;56(12):1694-1698. PubMed
  3. Moisey, L. L., Robinson, L. E., and Graham, T. E. Consumption of caffeinated coffee and a high carbohydrate meal affects postprandial metabolism of a subsequent oral glucose tolerance test in young, healthy males. Br.J Nutr. 2010;103(6):833-841. PubMed
  4. Buscemi, S., Verga, S., Batsis, J. A., Donatelli, M., Tranchina, M. R., Belmonte, S., Mattina, A., Re, A., and Cerasola, G. Acute effects of coffee on endothelial function in healthy subjects. Eur.J Clin Nutr. 2010;64(5):483-489. PubMed
  5. Orozco-Gregorio, H., Mota-Rojas, D., Bonilla-Jaime, H., Trujillo-Ortega, M. E., Becerril-Herrera, M., Hernandez-Gonzalez, R., and Villanueva-Garcia, D. Effects of administration of caffeine on metabolic variables in neonatal pigs with peripartum asphyxia PubMed
  6. van der Hoeven N, Visser I, Schene A, van den Born BJ. Severe hypertension related to caffeinated coffee and tranylcypromine: a case report. Ann Intern Med. 2014 May 6;160(9):657-8. doi: 10.7326/L14-5009-8. No abstract available. 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

Guarana Also Interacts With Other Medications

Guarana has 8 major, 461 moderate, 185 minor known drug interactions in our database — the Phenelzine Sulfate one above is one of them. If you take anything else, check it against the full list below.

Major 8 Moderate 461 Minor 185 No known interaction 2,176 (incl. Phenelzine Sulfate)
Taking anything else?

Check Another of Your Medications Against Guarana

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

Everything else you take

See Every Supplement That Interacts With Phenelzine Sulfate

This page covers Guarana only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Phenelzine Sulfate page lists 144 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: 1,4-butanediol (major), Activated Charcoal (major), Beer (major), Bitter Orange (major) and Brewer's Yeast (major).

By severity: 18 major · 111 moderate · 15 minor.

From our pharmacist’s overview on the Phenelzine Sulfate page

“Few medications demand as much dietary and supplement care as phenelzine sulfate (Nardil), an older MAOI antidepressant, and this list backs that up, with 18 of its 144 recorded interactions rated major. The two dominant themes are sedation and blood pressure.”

Reviewed by 2 · Jul 18, 2026

Open the Phenelzine Sulfate interaction page

One more smart check

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

We hold 1,430 real supplement products containing Guarana, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Guarana. Your product may carry other ingredients that interact with Phenelzine Sulfate too, on top of Guarana — 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 Guarana and Phenelzine Sulfate 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 Guarana
Top 10%

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

29 days ago today
Medication Phenelzine Sulfate
Top half

#1,119 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 Guarana

What is Guarana?

Guarana
  • Energy and alertness
  • Reducing fatigue
  • Weight loss support
  • Athletic performance
  • Mental focus

Guarana is an Amazonian seed that is naturally high in caffeine, which explains most of its stimulant and energy effects. While it may give a short-term boost in alertness and reduce fatigue, strong evidence for weight loss or major performance gains is limited, and it carries the same risks as too much caffeine. Talk to your pharmacist or doctor before using it, especially if you have heart problems, anxiety, or are pregnant.

Read the full Guarana monograph & all interactions
Medication

About Phenelzine

What Is Phenelzine Used For?

Brand name: Nardil

Phenelzine is used to treat depression — specifically the types described as atypical, nonendogenous, or neurotic depression. This often includes people who have a mix of anxiety and depression, or who have phobic or hypochondriacal features (strong fears about illness or physical symptoms).

It is generally not the first antidepressant a doctor will try. It is best suited for patients who have already tried other antidepressants without enough relief. There is less evidence supporting its use in severe depression with classic biological features (called endogenous depression).

See full Phenelzine drug information
Keep checking

Other Drugs & Guarana

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

8Major
461Moderate
185Minor
2,175No known interaction
8 Major 461 Moderate 185 Minor 2,175 No interaction
Major

8 interactions

Moderate

461 interactions

Showing 60 of 461 moderate interactions — see all 461 on the Guarana page.

Minor

185 interactions

Showing 60 of 185 minor interactions — see all 185 on the Guarana page.

No interaction 2,175 drugs checked — show the list

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

Showing the 60 most looked-up of 2,175 medications checked with no known interaction — see the full Guarana list.

See the full Guarana interactions page
See every supplement checked against Phenelzine Sulfate, 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
Guarana monograph › Uses, safety, and every drug interaction in one place Phenelzine Sulfate supplement interactions › Every supplement checked against Phenelzine Sulfate, ranked by severity Phenelzine 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 Guarana and Phenelzine Sulfate Together: Common Questions

Can you take Guarana with Phenelzine Sulfate?
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.
How serious is the Guarana and Phenelzine Sulfate 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 Phenelzine Sulfate and Guarana?

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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.