Linezolid Injection and Phenylpropanolamine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Linezolid Injection
Phenylpropanolamine
No brand names on record
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.
What happens
An increase in blood pressure
Interaction Deep Dive
Concomitant use of linezolid and indirectly acting sympathomimetic agents, such as phenylpropanolamine, is contraindicated in the absence of monitoring for potential blood pressure increases. Linezolid is a reversible, nonselective inhibitor of monoamine oxidase and may therefore interact with phenylpropanolamine. Patients may experience reversible enhancement of the pressor response to phenylpropanolamine1.
Why it happens (mechanism)
Inhibition of phenylpropanolamine metabolism
Literature reports
1 report — tap to read
a) Plasma concentration and area under the concentration-time curve (AUC) of phenylpropanolamine were increased when coadministered with linezolid. Participants received 2 doses of phenylpropanolamine (or matching placebo) 4 hours apart, alone on days 1, and with concomitantly administered linezolid tablets 600 mg (every 12 hours on days 4 to 9) on days 7 and 9. Linezolid has minimal effect on the pharmacokinetics of phenylpropanolamine with increases of 30% (p=0.0001) in AUC and 20% (p=0.0006) in Cmax for phenylpropanolamine. The pharmacokinetic parameters of linezolid were not changed significantly when administered with phenylpropanolamine. Statistically significant increases in systolic blood pressure were observed as compared to placebo. This population of patients was minimally affected by the level of sympathomimetic potentiation due to linezolid. However, patients sensitive to the effects of increased blood pressure due to predisposing factors should be treated with linezolid and phenylpropanolamine cautiously 2.
Common questions
Can I take Linezolid Injection and Phenylpropanolamine together?
An increase in blood pressure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Linezolid Injection and Phenylpropanolamine 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 "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Linezolid Injection or Phenylpropanolamine 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: ZYVOX(R) IV injection, oral tablets, oral suspension, linezolid IV injection, oral tablets, oral suspension. Pharmacia and Upjohn Company, New York, NY, 2008.
- Hendershot P, Antal E, Welshman I, et al: Linezolid: pharmacokinetic and pharmacodynamic evaluation of coadministration with pseudoephedrine HCl, phenylpropanolamine HCl, and dextromethorphan HBr. J Clin Pharmacol 2001; 41:563-572. DOI
Keep reading about Linezolid Injection
Keep reading about Phenylpropanolamine
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