Chloramphenicol Injection and Cyanocobalamin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Chloramphenicol Injection
Cyanocobalamin
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
Decreased efficacy of cyanocobalamin when used to treat anemia
Interaction Deep Dive
If chloramphenicol is used concomitantly with cyanocobalamin patients being treated for anemia, monitor for reduced cyanocobalamin efficacy and consider alternative therapy1.
Why it happens (mechanism)
Antagonism
Common questions
Can I take Chloramphenicol Injection and Cyanocobalamin together?
Decreased efficacy of cyanocobalamin when used to treat anemia Always confirm with your pharmacist or prescriber before making any change.
How serious is the Chloramphenicol Injection and Cyanocobalamin interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
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 Chloramphenicol Injection or Cyanocobalamin 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 anything you'd monitor while I'm on both?
References (1)
- Product Information: Nascobal(R) nasal spray, cyanocobalamin nasal spray. Par Pharmaceutical Companies Inc (per FDA), Chestnut Ridge, NY, 2018. DailyMed
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