Dalfopristin and Disopyramide: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Disopyramide
Dalfopristin
No brand names on record
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
An increased risk of disopyramide toxicity (cardiac arrhythmias, hypotension, syncope)
Interaction Deep Dive
Quinupristin/dalfopristin is a potent inhibitor of cytochrome P450 3A4 enzymes and may cause an increase in disopyramide concentrations when administered concurrently. Because disopyramide possesses a narrow therapeutic window, patients should be closely monitored during concomitant therapy, and doses of disopyramide should be adjusted accordingly1.
Why it happens (mechanism)
Inhibition of cytochrome P450 3A4-mediated disopyramide metabolism
Common questions
Can I take Dalfopristin and Disopyramide together?
An increased risk of disopyramide toxicity (cardiac arrhythmias, hypotension, syncope) Always confirm with your pharmacist or prescriber before making any change.
How serious is the Dalfopristin and Disopyramide 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 Dalfopristin or Disopyramide 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: Synercid(R) I.V. quinupristin and dalfopristin. Rhone-Poulenc Rorer Pharmaceuticals Inc. Collegeville, PA, 1999.
Keep reading about Disopyramide
Keep reading about Dalfopristin
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