Phenylalanine + Phenelzine Sulfate
Phenelzine Sulfate brand name: Nardil.
Phenylalanine has a moderate interaction with Phenelzine Sulfate. Theoretically, concomitant use of L-phenylalanine and non-selective MAOIs might increase the risk of hypertensive crisis.
Read the full interaction reportPhenylalanine and Phenelzine Sulfate
Here is the interaction we found between these two, with the evidence behind it.
MONOAMINE OXIDASE INHIBITORS (MAOIs)
Why this applies to Phenelzine Sulfate
Phenelzine Sulfate falls under MONOAMINE OXIDASE INHIBITORS (MAOIs) — the group Phenylalanine interacts with.
L-phenylalanine is metabolized to tyrosine. Some evidence suggests that L-phenylalanine, given with the non-selective MAOI pargyline, might prevent the elimination of tyramine, increasing the risk of hypertensive crisis. However, this was not reported in a small number of patients when using L-phenylalanine with the partially selective MAO-B inhibitor, selegiline.
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.
Here's the concern with pairing phenylalanine and Nardil (phenelzine). Phenelzine is an MAOI, meaning it blocks the enzyme that normally breaks down certain stimulating substances in your body. Your body turns L-phenylalanine into tyrosine, and there's some lab-based thinking that it may also slow the clearing of tyramine, a compound that can spike blood pressure. With that breakdown pathway already blocked by phenelzine, the worry is a hypertensive crisis, a dangerous surge in blood pressure that can bring on a pounding headache, neck stiffness, chest pain, or a racing heart.
I'll be honest: this is mostly theoretical, drawn from animal and lab studies, not solid human reports. Still, because phenelzine already requires careful diet limits, I wouldn't add a phenylalanine supplement without first checking with your doctor or pharmacist.
- Silkaitis RP, Mosnaim AD. Pathways linking L-phenylalanine and 2-phenylethylamine with p-tyramine in rabbit brain. Brain Res 1976;114:105-15.
- Lehmann WD, Theobald N, Fischer R, Heinrich HC. Stereospecificity of phenylalanine plasma kinetics and hydroxylation in man following oral application of a stable isotope-labelled pseudo-racemic mixture of L- and D-phenylalanine. Clin Chim Acta 1983;128 PubMed
- Birkmayer W, Riederer P, Linauer W, Knoll J. L-deprenyl plus L-phenylalanine in the treatment of depression. J Neural Transm 1984;59:81-7. PubMed
- Baker GB, Bornstein RA, Rouget AC, et al. Phenylethylaminergic mechanisms in attention-deficit disorder. Biol Psychiatry 1991;29:15-22.. PubMed
What These Ratings Mean
Every interaction above is graded three ways — here’s the key to each label.
Clinically significant. Avoid the combination, or use only under close professional supervision.
Usually worth avoiding or managing — may need monitoring, a dose change, or timing apart.
Generally not serious. Be aware of it and mention it to your pharmacist.
- 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.
- 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.
Phenylalanine Also Interacts With Other Medications
Phenylalanine has 5 major, 10 moderate 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.
Check Another of Your Medications Against Phenylalanine
We haven’t checked that one against Phenylalanine yet — ask our pharmacists directly.
Covers the 2,830 medications we’ve checked against Phenylalanine. Pick one to open its full report.
See Every Supplement That Interacts With Phenelzine Sulfate
This page covers Phenylalanine 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
Taking Phenylalanine as Part of a Dietary Supplement Product? Check It for Interactions
We hold 1,990 real supplement products containing Phenylalanine, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Phenylalanine. Your product may carry other ingredients that interact with Phenelzine Sulfate too, on top of Phenylalanine — and those would not show on this page. Find your product and we’ll check every ingredient on its label:
Where Phenylalanine 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.
#118 of 1,452 supplements looked up here in the last 7 days
#1,119 of 2,830 medications looked up here in the last 7 days
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.
About Phenylalanine
What is Phenylalanine?
- Depression and mood
- Skin condition vitiligo
- Pain conditions
- Attention and focus
- Appetite control
Phenylalanine is an essential amino acid the body uses to make brain chemicals like dopamine and norepinephrine. Some people take it for mood, vitiligo, or pain, but the evidence is mostly limited or mixed. People with the genetic condition PKU must strictly avoid it.
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).
Other Drugs & Phenylalanine
Browse every other medication we’ve checked against Phenylalanine — both the ones with a known interaction and the ones without. Select any drug for the full detail.
No drugs match “”.
5 interactions
10 interactions
No interaction 2,814 drugs checked — show the list
We also checked Phenylalanine against these medications and found no known interaction in our sources. Open any page to confirm.
- Apixaban ›
- Levothyroxine ›
- Amlodipine ›
- Methylphenidate ›
- Warfarin ›
- Sertraline ›
- Testosterone ›
- Losartan Potassium ›
- Metoprolol ›
- Aspirin ›
- Ivermectin ›
- Rivaroxaban ›
- Rosuvastatin ›
- Escitalopram ›
- Tadalafil ›
- Acetaminophen ›
- Clopidogrel ›
- Valacyclovir ›
- Atorvastatin ›
- Docusate ›
- Hydroxyurea ›
- Abemaciclib ›
- Methamphetamine ›
- Ibuprofen ›
- Sumatriptan ›
- Semaglutide ›
- Tirzepatide ›
- Warfarin Sodium ›
- Prednisone ›
- Propranolol ›
- Lisdexamfetamine ›
- Acyclovir ›
- Bupropion ›
- Metformin ›
- Amoxicillin ›
- Lisinopril ›
- Bendamustine ›
- Amitriptyline ›
- Doxycycline ›
- Lamotrigine ›
- Fluoxetine ›
- Methotrexate ›
- Acetaminophen, Codeine ›
- Gabapentin ›
- Pregabalin ›
- Isotretinoin ›
- Dextroamphetamine ›
- Azithromycin ›
- Clonazepam ›
- Quetiapine ›
- Omeprazole ›
- Amlodipine Besylate ›
- Methylene Blue ›
- Duloxetine ›
- Letrozole ›
- Buspirone ›
- Citalopram ›
- Ciprofloxacin ›
- Naproxen ›
- Bisoprolol ›
Showing the 60 most looked-up of 2,814 medications checked with no known interaction — see the full Phenylalanine list.
Sources & How We Checked
Interaction details are evidence-graded and sourced from the Natural Medicines database. The medication overview comes from MedlinePlus.
- Natural Medicines (Therapeutic Research Center) — Evidence-graded clinical reference for vitamins, herbs and supplements — the basis for our interaction data.
- MedlinePlus, U.S. National Library of Medicine — NIH consumer drug information, used for the medication overviews.
- NIH Dietary Supplement Label Database (DSLD) — Official supplement product labels.
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
Phenelzine Sulfate Is Linked to Lower Levels of One Nutrient
Natural Medicines records Phenelzine Sulfate as a medicine that can lower these. This is not an interaction with Phenylalanine — it is a separate effect of the medicine, and it is a reason some people are advised to supplement rather than to avoid one:
Read the full Phenelzine Sulfate nutrient depletion report ›
Depletion records come from the licensed Natural Medicines database. Do not start a supplement on the strength of this page — ask your pharmacist or doctor whether it applies to you.
Taking Phenylalanine and Phenelzine Sulfate Together: Common Questions
Can you take Phenylalanine with Phenelzine Sulfate?
How serious is the Phenylalanine and Phenelzine Sulfate interaction?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
Still Have a Question About Phenelzine Sulfate and Phenylalanine?
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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.