Guanethidine and Linezolid Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Linezolid Injection
Guanethidine
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
Reduced antihypertensive response to guanethidine and an increased risk of hypertensive crisis
Interaction Deep Dive
The concurrent use of guanethidine and an MAOI is contraindicated. Guanethidine inhibits norepinephrine release from neuronal storage sites in response to stimulation of the nerve and causes depletion of norepinephrine from nerve endings. Nonselective MAO inhibitors may antagonize the antihypertensive effects of guanethidine. In addition, the initiation of guanethidine therapy in a patient receiving a nonselective MAO inhibitor could result in hypertensive emergency1.
Why it happens (mechanism)
Release of catecholamines
Common questions
Can I take Guanethidine and Linezolid Injection together?
Reduced antihypertensive response to guanethidine and an increased risk of hypertensive crisis Always confirm with your pharmacist or prescriber before making any change.
How serious is the Guanethidine and Linezolid Injection 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 Guanethidine or Linezolid Injection 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 (1)
- Product Information: Ismelin(R), guanethidine. Ciba-Geneva Pharmaceuticals, Summit, NJ, 1996.
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