Phenylalanine + Mexiletine
Mexiletine brand name: Mexitil.
We found no known interaction between Phenylalanine and Mexiletine in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, the label for Mexiletine states a food rule worth keeping to, and the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.
Phenylalanine and Mexiletine
We checked these two against our interaction database. Here is what we found.
No Known Interaction Found
We did not find a documented interaction between Mexiletine and Phenylalanine in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.
If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.
Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.
Phenylalanine safety at a glance
Pregnancy & breastfeeding ratings are from Natural Medicines (Therapeutic Research Center) — the full detail is in the Special populations card below. Safety guidance is general; always confirm with your pharmacist or doctor for your situation.
Why No Interaction Is Listed for Mexiletine
Interactions in our licensed database are recorded against drug classes, not just single drug names. Mexiletine is filed under 7 classifications — including cytochrome p450 1a2 (cyp1a2) inhibitors, cytochrome p450 1a2 (cyp1a2) substrates, cytochrome p450 1a2 (cyp1a2) substrates. Phenylalanine has documented interactions with 3 drug classes — the most serious being levodopa (major), baclofen (moderate) and monoamine oxidase inhibitors (maois) (moderate) — and none of Mexiletine’s classifications are among them.
Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.
Phenylalanine Does Interact With Other Medications
Phenylalanine has 5 major, 11 moderate known drug interactions in our database — Mexiletine isn’t 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.
Phenylalanine in Pregnancy & Breastfeeding
When L-phenylalanine is consumed in amounts typically found in foods by pregnant patients with normal phenylalanine metabolism.
When L-phenylalanine is consumed in amounts typically found in foods by pregnant patients with high serum phenylalanine concentrations, such as those with phenylketonuria (PKU). Serum levels of phenylalanine greater than 360 micromol/L increase the risk of birth defects. Experts recommend that patients with high phenylalanine serum concentrations follow a low phenylalanine diet for at least 20 weeks prior to conception to decrease the risk for birth defects. There is insufficient reliable information available about the safety of L-phenylalanine when taken by mouth in large doses during pregnancy; avoid using. There is insufficient reliable information available about the safety of oral D-phenylalanine during pregnancy; avoid using.
When L-phenylalanine is consumed in amounts typically found in foods by breast-feeding patients with normal phenylalanine metabolism. There is insufficient reliable information available about the safety of L-phenylalanine when taken by mouth in medicinal amounts during lactation; avoid using. There is insufficient reliable information available about the safety of oral D-phenylalanine during lactation; avoid using.
DISCLAIMER: This tool is intended for informational purposes only, and should not be interpreted as specific medical advice. Patients should consult with a qualified healthcare provider before making decisions about therapies and/or health conditions.© 2026 Therapeutic Research Center
Some Mexiletine Products Have a Food Rule — Phenylalanine Should Not Break It
At least one FDA label for a product containing Mexiletine says to take it with food. If you take Phenylalanine on an empty stomach out of habit, keep them separate — and take Mexiletine with a meal where the label says to.
This may not be true of your version. Food instructions belong to the product, not the ingredient: two Mexiletine products can carry different directions, and extended-release forms often differ from immediate-release ones. The label we read is quoted below — check the directions on your own box or bottle, or ask your pharmacist, for how to take the exact product you were given.
Administration with food or antacid is recommended.
From the Dosage and Administration section of the FDA label we read for Mexiletine — where that label names a specific product, the instruction is that product's. Read the label on DailyMed ›
A food rule is not an interaction — it is about how much of the medicine you absorb. The directions that came with your own product, and your pharmacist, outrank anything on this page.
See Every Supplement That Interacts With Mexiletine
This page covers Phenylalanine only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Mexiletine page lists 152 supplements it has a documented interaction with, worst first, each one explained.
The most serious there right now: Activated Charcoal (major), 1,3-dmaa (moderate), Acacia Rigidula (moderate), Active Hexose Correlated Compound (ahcc) (moderate) and Adrafinil (moderate).
By severity: 1 major · 107 moderate · 44 minor.
From our pharmacist’s overview on the Mexiletine page
“Mexiletine (Mexitil) steadies the heart's rhythm, and its benefit depends on holding a fairly precise blood level, so the 152 supplements on this list deserve real attention rather than a shrug. Only one entry, activated charcoal, is rated major, because it can soak up the drug in the gut and cut how much actually reaches your bloodstr…”
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. Even though Phenylalanine itself has no known interaction with Mexiletine, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:
Where Phenylalanine and Mexiletine 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
#552 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.
Where does our data come from?
- Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
- Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Phenylalanine reference on this page ↓
- Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Phenylalanine and Mexiletine records this page draws on were last updated July 11, 2026.
- What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
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.
Amino acid (not a plant part) · Capsules, tablets, powder
An interaction check asks whether these two react with each other — it does not ask whether Phenylalanine is a good idea for someone in your situation. Here is what our Phenylalanine record says about it on its own.
Phenylalanine: dosing
There is no well-established standard supplement dose for phenylalanine, and the right amount may differ depending on the form (L-, D-, or DL-) and the reason for use.If you choose to use a product, follow the directions on the label and do not exceed the recommended amount.
From our Phenylalanine monograph — the full record covers uses, side effects and every documented interaction.
About Mexiletine
What Is Mexiletine Used For?
Brand name: Mexitil
Mexiletine Hydrochloride capsules are indicated for the treatment of documented, life-threatening ventricular arrhythmias — for example, sustained ventricular tachycardia (a dangerously fast heart rhythm originating in the lower chambers). Because mexiletine itself can trigger arrhythmias, it is not recommended for minor or symptom-free irregular heartbeats.
Treatment is started in a hospital setting so heart rhythm can be monitored closely. Antiarrhythmic drugs, including mexiletine, have not been shown to improve overall survival in patients with ventricular arrhythmias.
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
11 interactions
No interaction 2,813 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 ›
- Ivermectin ›
- Aspirin ›
- Rivaroxaban ›
- Rosuvastatin ›
- Escitalopram ›
- Acetaminophen ›
- Tadalafil ›
- Clopidogrel ›
- Atorvastatin ›
- Docusate ›
- Abemaciclib ›
- Hydroxyurea ›
- Valacyclovir ›
- Ibuprofen ›
- Methamphetamine ›
- Semaglutide ›
- Sumatriptan ›
- Tirzepatide ›
- Warfarin Sodium ›
- Prednisone ›
- Propranolol ›
- Lisdexamfetamine ›
- Bupropion ›
- Metformin ›
- Amoxicillin ›
- Lisinopril ›
- Bendamustine ›
- Acyclovir ›
- Amitriptyline ›
- Methotrexate ›
- Doxycycline ›
- Fluoxetine ›
- Acetaminophen, Codeine ›
- Lamotrigine ›
- Pregabalin ›
- Gabapentin ›
- Dextroamphetamine ›
- Azithromycin ›
- Isotretinoin ›
- Methylene Blue ›
- Clonazepam ›
- Omeprazole ›
- Amlodipine Besylate ›
- Quetiapine ›
- Duloxetine ›
- Letrozole ›
- Buspirone ›
- Naproxen ›
- Citalopram ›
- Ciprofloxacin ›
- Bisoprolol ›
Showing the 60 most looked-up of 2,813 medications checked with no known interaction — see the full Phenylalanine list.
Phenylalanine References
The 23 references that drive our Phenylalanine monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.
- Rouse B, Azen C, Koch R, et al. Maternal phenylketonuria collaborative Study (MPKUCS) offspring: facial anomalies, malformations, and early neurological sequelae. Am J Med Genet 1997;69:89-95. DOI
- Sturtevant FM. Use of aspartame in pregnancy. Int J Fertil 1985;30:85-7.
- 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
- Mosnik DM, Spring B, Rogers K, Baruah S. Tardive dyskinesia exacerbated after ingestion of phenylalanine by schizophrenic patients. Neuropsychopharmacology 1997;16:136-46. PubMed
- Siddiqui AH, Stolk LM, Bhaggoe R, et al. L-phenylalanine and UVA irradiation in the treatment of vitiligo. Dermatology 1994;88:215-8. 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
- Nutt JG, Woodward WR, Hammerstad JP, et al. The "on-off" phenomenon in Parkinson's disease. Relation to levodopa absorption and transport. N Engl J Med 1984;310:483-8. PubMed
- Baruzzi A, Contin M, Riva R, et al. Influence of meal ingestion time on pharmacokinetics of orally administered levodopa in parkinsonian patients. Clin Neuropharmacol 1987;10:527-37. PubMed
- Juncos JL, Fabbrini G, Mouradian MM, et al. Dietary influences on the antiparkinsonian response to levodopa. Arch Neurol 1987;44:1003-5. PubMed
- Eriksson T, Granerus AK, Linde A, et al. "On-off" phenomenon in Parkinson's disease: relationship between dopa and other large neutral amino acids in plasma. Neurology 1988;38:1245-8. PubMed
- Baker GB, Bornstein RA, Rouget AC, et al. Phenylethylaminergic mechanisms in attention-deficit disorder. Biol Psychiatry 1991;29:15-22.. PubMed
- Wood DR, Reimherr FW, Wender PH. Treatment of attention deficit disorder with DL-phenylalanine. Psychiatry Res 1985;16:21-6.. PubMed
- Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, DC: National Academy Press, 2002. Available at: http://www.n
- Cederbaum S. Phenylketonuria: an update. Curr Opin Pediatr 2002;14:702-6. PubMed
- Cejudo-Ferragud, E., Nacher, A., Polache, A., Cercos-Fortea, T., Merino, M., and Casabo, V. G. Evidence of competitive inhibition for the intestinal absorption of baclofen by phenylalanine. Int J of Pharm (Amsterdam) 1996;132:63-69. DOI
- Fischer, E., Heller, B., Nachon, M., and Spatz, H. Therapy of depression by phenylalanine. Preliminary note. Arzneimittelforschung. 1975;25(1):132.
- Beckmann, H., Strauss, M. A., and Ludolph, E. Dl-phenylalanine in depressed patients: an open study. J.Neural Transm. 1977;41(2-3):123-134. PubMed
- Sabelli, H. C., Fawcett, J., Gusovsky, F., Javaid, J. I., Wynn, P., Edwards, J., Jeffriess, H., and Kravitz, H. Clinical studies on the phenylethylamine hypothesis of affective disorder: urine and blood phenylacetic acid and phenylalanine dietary supplem
- Cotzias, G. C., Van Woert, M. H., and Schiffer, L. M. Aromatic amino acids and modification of parkinsonism. N Engl.J Med 2-16-1967;276(7):374-379. PubMed
- Kravitz, H. M., Sabelli, H. C., and Fawcett, J. Dietary supplements of phenylalanine and other amino acid precursors of brain neuroamines in the treatment of depressive disorders. J Am Osteopath.Assoc 1984;84(1 Suppl):119-123. DOI
- Mann, J., Peselow, E. D., Snyderman, S., and Gershon, S. D-phenylalanine in endogenous depression. Am.J.Psychiatry 1980;137(12):1611-1612. PubMed
- Katoulis AC, Alevizou A, Bozi E, et al. A randomized, double-blind, vehicle-controlled study of a preparation containing undecylenoyl phenylalanine 2% in the treatment of solar lentigines. Clin Exp Dermatol 2010;35(5):473-6. PubMed
Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.
Taking Phenylalanine and Mexiletine Together: Common Questions
Is it safe to take Phenylalanine with Mexiletine?
Do Phenylalanine and Mexiletine have any of the same side effects?
Should I take Phenylalanine and Mexiletine at the same time of day?
How was the Phenylalanine and Mexiletine combination checked?
Does Phenylalanine interact with any other medications?
Does Mexiletine interact with any supplements?
Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy
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