Drug Interaction Report

Linezolid Injection and Phenylalanine: Interaction Details

Name: Linezolid Injection and Phenylalanine Interaction
Creator: Dr. Brian Staiger, PharmD, BCPS

A pharmacist-reviewed analysis of the Linezolid Injection and Phenylalanine interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Linezolid Injection

Zyvox Zyvox®

Phenylalanine

No brand names on record

Medically reviewed by

Dr. Brian Staiger, PharmD, BCPS

Updated Aug 8, 2026

Editorial policy · Data sources

Interaction severity

Contraindicated

These should generally not be used together.

Minor

Moderate

Major

Contraindicated

How we grade severity & evidence

Severity levels

Contraindicated: These should generally not be used together.
Major: Potentially serious — often needs a change or close monitoring.
Moderate: Can be significant — usually manageable with monitoring.
Minor: Usually limited clinical impact.

Evidence grades

Established: Well documented — supported by controlled studies or strong clinical data.
Probable: Good supporting evidence, though not definitively proven.
Suspected: Some evidence suggests this interaction, but it is not well established.
Possible: Limited or conflicting evidence; the interaction may occur.
Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.

Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.

Of 212 documented Linezolid Injection interactions, 98 are rated contraindicated — including this one.

Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.

Onset

rapid

Evidence

theoretical

Severity

Contraindicated

What happens

Increased risk of hypertensive crisis (headache, palpitation, neck stiffness)

Interaction Deep Dive

Phenylalanine is contraindicated in patients taking monoamine oxidase inhibitors¹. Concomitant use of phenylalanine with various non-selective monoamine-oxidase inhibitors may prevent elimination of tyramine, thus increasing the risk of hypertensive crisis ². Coadministration may result in hypertensive crisis, which is characterized by symptoms such as occipital headache, palpitation, neck stiffness, nausea, and vomiting. Hypertensive crisis associated with monoamine oxidase inhibitors may be fatal ¹.

Why it happens (mechanism)

Interference with tyramine metabolism resulting in increased catecholamine availability

Common questions

Can I take Linezolid Injection and Phenylalanine together?

Increased risk of hypertensive crisis (headache, palpitation, neck stiffness) Always confirm with your pharmacist or prescriber before making any change.

How serious is the Linezolid Injection and Phenylalanine interaction?

It is rated contraindicated. These should generally not be used together.

How quickly could this interaction happen?

The documented onset is "rapid". Effects can appear quickly, often within about 24 hours of combining the drugs.

How strong is the evidence for this interaction?

The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.

Questions for your pharmacist

Does my dose of Linezolid Injection or Phenylalanine need adjusting while I take them together?
What symptoms should prompt me to call you or my prescriber right away?
Does the timing of my doses matter for this combination?
Is there a safer alternative to one of these medications for me?

References (2)

Product Information: NARDIL(R) oral film coated tablets, phenelzine sulfate oral film coated tablets. Parke-Davis Div of Pfizer Inc (per DailyMed), New York, NY, 2020. DailyMed
Silkaitis RP & Mosnaim AD: Pathways linking L-phenylalanine and 2-phenylethylamine with p-tyramine in rabbit brain. Brain Res 1976; 114(1):105-115.

Was this write-up helpful?

Linezolid Injection

Keep reading about Linezolid Injection

All Linezolid Injection interactions (212) Linezolid Injection drug information

Also serious with: Tramadol Tranylcypromine Trazodone Trimipramine

Phenylalanine

Keep reading about Phenylalanine

All Phenylalanine interactions (2)

Check another combination

Our instant two-drug interaction checker is almost here.

Coming soon

The instant two-drug checker is on its way.

In the meantime, browse the directory below to look up any drug and see its documented interactions.

Still have questions about this combination?

Every question gets a real answer from a licensed pharmacist — free, and usually within a day.

Ask the pharmacist

A message from HelloPharmacist

About our interaction database: depth, not breadth

HelloPharmacist doesn't license one of the big commercial interaction databases, so what you'll find here is not a complete list of every known drug interaction. Instead, each entry is researched, analyzed, and written up individually — documented from the published literature, reviewed by a pharmacist, and cited so you can check every source yourself.

If a combination isn't listed here, it means we haven't documented it yet — never that it's safe. For screening a full medication list, we recommend pairing this site with a comprehensive tool like the Drugs.com Interaction Checker and, most importantly, a review by your own pharmacist. For a deep, plain-English, fully sourced explanation of a specific documented interaction — that's exactly what we built this for.

This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.