Pentamidine and Azithromycin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Azithromycin
Pentamidine
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
Increased risk of QT interval prolongation
Interaction Deep Dive
Concomitant use of azithromycin and pentamidine, both drugs that prolong the QT interval, may result in additive effects on QT interval prolongation and an increased risk of torsade de pointes. Therefore, use caution when these agents are given concurrently12 and consider the risk of QT prolongation which can be fatal 1.
Why it happens (mechanism)
Additive QT interval prolongation
Common questions
Can I take Pentamidine and Azithromycin together?
Increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Pentamidine and Azithromycin interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Pentamidine or Azithromycin 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: ZMAX(R) oral extended-release suspension, azithromycin oral extended-release suspension. Pfizer Inc (per FDA), New York, NY, 2021. DailyMed
- Lindsay J Jr, Smith MA, & Light JA: Torsades de pointes associated with antimicrobial therapy for pneumonia. Chest 1990; 98:222-223. PubMed
Keep reading about Azithromycin
Keep reading about Pentamidine
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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