Colistimethate Injection and Gentamicin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Colistimethate Injection
Gentamicin
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
Respiratory depression
Interaction Deep Dive
Concurrent and/or sequential use of gentamicin with other neurotoxic or nephrotoxic products, such as colistin, should be avoided2 as both aminoglycosides and colistin have been reported to interfere with nerve transmission at the neuromuscular junction. If coadministration is necessary, it should be done with great caution 1.
Why it happens (mechanism)
Additive neuromuscular blocking effects
Common questions
Can I take Colistimethate Injection and Gentamicin together?
Respiratory depression Always confirm with your pharmacist or prescriber before making any change.
How serious is the Colistimethate Injection and Gentamicin interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
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 Colistimethate Injection or Gentamicin 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: Coly-Mycin(R) M Parenteral IV and IM injection, Colistimethate IV and IM injection. JHP Pharmaceuticals LLC, Rochester, MI, 2007.
- Product Information: gentamicin IM, IV injection, gentamicin IM, IV injection. APP Pharmaceuticals, LLC (per Manufacturer), Schaumburg, IL, 2008.
Keep reading about Colistimethate Injection
Keep reading about Gentamicin
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