Drug Interaction Report

Dofetilide and Pentamidine: Interaction Details

A pharmacist-reviewed analysis of the Dofetilide and Pentamidine interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Dofetilide

Tikosyn Tikosyn®
+

Pentamidine

NebuPent Pentam
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
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.

Of 454 documented Dofetilide interactions, 288 are rated major — including this one.
Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.
Onset
unspecified
Evidence
theoretical
Severity
Major

What happens

An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest)

Interaction Deep Dive

Class III antiarrhythmics and pentamidine have been shown to prolong the QTc interval at the recommended therapeutic dose13. Even though no formal drug interaction studies have been done, the coadministration of Class III and other drugs known to prolong the QTc interval, including pentamidine, is not recommended 24.

Why it happens (mechanism)

Additive effects on QT prolongation

Literature reports

1 report — tap to read

a) Concurrent use of class III antiarrhythmic agents, and other drugs that can prolong the QT interval, such as pentamidine, is not recommended. Dofetilide should be stopped for at least 2 days before any interacting drug is initiated. If concurrent use cannot be avoided, cautious dosing and telemetric monitoring is advised 2.

Common questions

Can I take Dofetilide and Pentamidine together?

An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Always confirm with your pharmacist or prescriber before making any change.

How serious is the Dofetilide and Pentamidine 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 Dofetilide or Pentamidine 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)

  1. Allen MJ, Nichols DJ, & Oliver SD: The pharmacokinetics and pharmacodynamics of oral dofetilide after twice daily and three times daily dosing. Br J Clin Pharmacol 2000; 50:247-253. PubMed
  2. Yamreudeewong W, DeBisschop M, Martin LG, et al: Potentially significant drug interactions of class III antiarrhythmic drugs. Drug Safety 2003; 26(6):421-438. PubMed
  3. Lindsay J Jr, Smith MA, & Light JA: Torsades de pointes associated with antimicrobial therapy for pneumonia. Chest 1990; 98:222-223. PubMed
  4. Product Information: Tikosyn(TM), dofetilide. Pfizer Inc, New York, NY, 1999. DailyMed
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Dofetilide

Keep reading about Dofetilide

All Dofetilide interactions (454) Dofetilide drug information
Also serious with: Bictegravir Cimetidine Saquinavir Cisapride
Pentamidine

Keep reading about Pentamidine

All Pentamidine interactions (56)
Also serious with: Moxifloxacin Oxaliplatin Injection Lenvatinib Histrelin Implant
Beyond drug–drug

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:

Dofetilide + Activated Charcoal American Hellebore Arsenic Cesium Ephedra Grapefruit Sida Cordifolia St. John's Wort + 138 more
Pentamidine + American Hellebore Arsenic Asarabacca Cesium Ephedra Grapefruit Siberian Cocklebur Sida Cordifolia + 70 more

major · moderate · minor — check everything you take with our drug–supplement interaction checker.

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This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.