Drug Interaction Report

Linezolid Injection and Phenylephrine: Interaction Details

A pharmacist-reviewed analysis of the Linezolid Injection and Phenylephrine 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

Phenylephrine

Biorphen Children's Sudafed PE Nasal Decongestant® Immphentiv Little Noses Decongestant Lusonal® Medicone Hemorrhoidal Mydfrin Nasop
+

Linezolid Injection

Zyvox Zyvox®
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Contraindicated
These should generally not be used together.
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
unspecified
Evidence
theoretical
Severity
Contraindicated

What happens

Increased blood pressure

Interaction Deep Dive

Concomitant use of linezolid and sympathomimetic agents, such as phenylephrine1, is contraindicated in the absence of monitoring for potential blood pressure increases. Although not specifically studied with phenylephrine, the coadministration of linezolid with 2 doses of pseudoephedrine or phenylpropanolamine resulted in increased blood pressure in each group, with maximum blood pressure readings observed 2 to 3 hours after the second dose of phenylpropanolamine or pseudoephedrine administration. Levels returned to baseline 2 to 3 hours after the peak. Linezolid is a reversible, nonselective inhibitor of monoamine oxidase 2 and coadministration with phenylephrine should be approached with caution. When initiating phenylephrine in a patient receiving linezolid, use a small initial dose 1 and monitor for increased blood pressure.

Why it happens (mechanism)

Enhanced pressor response; inhibition of phenylephrine metabolism

Common questions

Can I take Linezolid Injection and Phenylephrine together?

Increased blood pressure Always confirm with your pharmacist or prescriber before making any change.

How serious is the Linezolid Injection and Phenylephrine interaction?

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

How quickly could this interaction happen?

The documented onset is "unspecified". The timing of this interaction is not well characterized.

How strong is the evidence for this interaction?

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

From our Q&A

Real reader questions about these medications, each personally answered by our pharmacist:

Questions for your pharmacist

  • Does my dose of Linezolid Injection or Phenylephrine 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)

  1. Product Information: phenylephrine hcl injection, 1%, phenylephrine hcl injection, 1%. Parenta Pharmaceuticals,Inc, West Columbia, SC, 2005. DailyMed
  2. Product Information: ZYVOX(R) intravenous injection, oral tablets, oral suspension, linezolid intravenous injection, oral tablets, oral suspension. Pharmacia & Upjohn Company (per FDA), New York, NY, 2011. DailyMed
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Phenylephrine

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All Phenylephrine interactions (6) Phenylephrine drug information
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Linezolid Injection

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All Linezolid Injection interactions (212) Linezolid Injection drug information
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Beyond drug–drug

These medications also interact with supplements

Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:

Phenylephrine + Activated Charcoal Ephedra Lithium Peyote Rauvolfia Vomitoria Sida Cordifolia 1,3-dmaa 1,3-dmba + 73 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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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.