Chloramphenicol Injection and Rifampin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Rifampin
Chloramphenicol Injection
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 chloramphenicol exposure
Interaction Deep Dive
Coadministration of rifAMPin and chloramphenicol may reduce chloramphenicol exposure123. In a number of case reports, the initiation of rifAMPin in patients on chloramphenicol resulted in a decline of chloramphenicol concentrations by as much as 90% (range 64 to 94%) 46.
Why it happens (mechanism)
Increased hepatic metabolism
Literature reports
2 reports — tap to read
a) Concomitant administration of rifAMPin and chloramphenicol caused a reduction in serum chloramphenicol levels in two patients 45. Three days after initiating rifAMPin 20 mg/kg daily, the chloramphenicol concentrations were reduced by 88.5% in one patient and by 63.8% in the other 4.
b) Concomitant administration of chloramphenicol and rifAMPin resulted in significant decreases in chloramphenicol serum concentrations in two young children (5-month-old boy, 18-month-old girl) with Haemophilus influenzae type b meningitis. Subsequent studies in animals (chimpanzees) documented an increase in chloramphenicol total body clearance after rifAMPin administration, as well as a decrease in the half-life and mean residence time. The monitoring of chloramphenicol serum levels with appropriate adjustments in dose during rifAMPin administration can maintain therapeutic serum levels; however, an increased dose of chloramphenicol could increase the risk of bone aplasia for the patient. High doses of chloramphenicol could increase the production of nitroso reduction products in the hepatic cytochrome P450 system; these compounds may be responsible for chloramphenicol-induced aplastic anemia. Due to these concerns, it was suggested that rifAMPin prophylaxis be delayed in chloramphenicol-treated patients with invasive Haemophilus influenzae type b infections until chloramphenicol is discontinued 6.
Common questions
Can I take Chloramphenicol Injection and Rifampin together?
Reduced chloramphenicol exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Chloramphenicol Injection and Rifampin interaction?
It is rated major. Potentially serious — often needs a change or close 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 Rifampin 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 (6)
- Product Information: RIFADIN(R) IV intravenous injection, rifampin intravenous injection. sanofi-aventis US LLC (per FDA), Bridgewater, NJ, 2023. DailyMed
- Product Information: RIFADIN(R) oral capsules, rifampin oral capsules. sanofi-aventis US LLC (per FDA), Bridgewater, NJ, 2023. DailyMed
- Product Information: RIFATER(R) oral tablets, rifampin, isoniazid, pyrazinamide oral tablets. sanofi-aventis US LLC (per FDA), Bridgewater, NJ, 2023. DailyMed
- Prober CG: Effect of rifampin on chloramphenicol levels (letter). N Engl J Med 1985; 312:788-789. PubMed
- Baciewicz AM, Self TH, & Bekemeyer WB: Update of rifampin drug interactions. Arch Intern Med 1987; 147:565-568.
- Kelly HW, Couch RC, Davis RL, et al: Interaction of chloramphenicol and rifampin. J Pediatr 1988; 112:817-820. PubMed
Keep reading about Rifampin
Keep reading about Chloramphenicol Injection
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