Rifampin and Doxycycline Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Rifampin
Doxycycline 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 doxycycline exposure and potential loss of doxycycline efficacy
Interaction Deep Dive
Coadministration of rifAMPin and doxycycline may reduce doxycycline exposure123. Concurrent rifAMPin may increase doxycycline clearance resulting in reduced doxycycline bioavailability 4.
Why it happens (mechanism)
Increased doxycycline clearance induced by rifAMPin
Literature reports
1 report — tap to read
a) Serum concentrations of doxycycline were lower when rifAMPin was coadministered compared with coadministration with streptomycin, in a study of 20 patients with brucellosis was conducted. Half of the study group was treated with the combination of doxycycline and rifAMPin and the other half with doxycycline and streptomycin. There was a significant inverse correlation between serum concentrations of rifAMPin and those of doxycycline. Clearance of doxycycline was 130% higher in the rifAMPin group compared with the streptomycin group. Doxycycline area under the concentration-time curve (AUC) and half-life (t1/2) were significantly lower in the group receiving concomitant rifAMPin compared with values for the group given streptomycin. Two of 10 patients in the rifAMPin group experienced therapeutic failure or relapse; all patients in the streptomycin group were cured. RifAMPin is a known inducer of hepatic metabolism. To date, the elimination process of doxycycline has not been fully defined; however, much of its clearance appears to be via hepatic metabolism. The mechanism of this interaction is likely to be rifAMPin induction of cytochrome P450 enzymes involved in doxycycline metabolism 4.
Common questions
Can I take Rifampin and Doxycycline Injection together?
Reduced doxycycline exposure and potential loss of doxycycline efficacy Always confirm with your pharmacist or prescriber before making any change.
How serious is the Rifampin and Doxycycline Injection 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 Rifampin or Doxycycline 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 (4)
- 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
- Colmenero JD, Fernandez-Gallardo LC, Agundez JAG, et al: Possible implications of doxycycline-rifampin interaction for treatment of brucellosis. Antimicrob Agents Chemother 1994; 38:2798-2802. PubMed
Keep reading about Rifampin
Keep reading about Doxycycline Injection
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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