Chloramphenicol Injection and Tolbutamide: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Chloramphenicol Injection
Tolbutamide
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
Hypoglycemia (CNS depression, seizures)
Interaction Deep Dive
Doses of 2 g chloramphenicol per day may increase TOLBUTamide levels by up to 90% and decrease blood glucose levels by 30%. Chloramphenicol has also been reported to increase chlorpropamide levels3124.
Why it happens (mechanism)
May decrease TOLBUTamide hepatic clearance
Common questions
Can I take Chloramphenicol Injection and Tolbutamide together?
Hypoglycemia (CNS depression, seizures) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Chloramphenicol Injection and Tolbutamide 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 Tolbutamide 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 (4)
- Christensen LK & Skovsted L: Inhibition of drug metabolism by chloramphenicol. Lancet 1969; 2:1397. DOI
- Petitpierre B & Fabre J: Chlorpropamide and chloramphenicol. Lancet 1970; 1:789. PubMed
- Brunova E, Slabochova Z, Platilova H, et al: Interaction of tolbutamide and chloramphenicol in diabetic patients. Int J Clin Pharmacol Biopharm 1977; 15:7-12.
- Petitpierre B, Perrin L, Rudhardt M, et al: Behaviour of chlorpropamide in renal insufficiency and under the effect of associated drug therapy. Int J Clin Pharmacol Ther Toxicol 1972; 6:120-124.
Keep reading about Chloramphenicol Injection
Keep reading about Tolbutamide
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