Itraconazole and Famotidine: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Itraconazole
Famotidine
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 itraconazole exposure and an increased risk of QT interval prolongation
Interaction Deep Dive
Concomitant use of itraconazole and agents that suppress or neutralize gastric pH (ie, proton pump inhibitors H2 blocker, and antacids) may result in decreased gastrointestinal absorption of itraconazole and decreased itraconazole plasma concentrations and bioavailability. Use caution when itraconazole is administered with acid neutralizing medicines or acid secretion suppressors. Antacids should be administered at least 2 hours before or 2 hours after itraconazole. Also, coadministration may result in additive QT interval prolongation12. In a study when itraconazole was coadministered with raNITIdine and antacids, serum concentrations of itraconazole were considerably lower compared with administration of itraconazole alone 3.
Why it happens (mechanism)
Reduced gastrointestinal absorption of itraconazole due to suppression or neutralization of gastric pH; additive QT interval prolongation
Literature reports
1 report — tap to read
a) The systemic availability of itraconazole was evaluated in 17 lung transplant recipients who were also taking raNITIdine 150 mg every 12 hours and antacids. In patients receiving itraconazole 200 mg and 400 mg daily, the median serum concentrations were 0.5 mcg/mL and 3.5 mcg/mL, respectively. These serum levels were considerably lower than the levels recorded from previous studies, which have reported a median itraconazole serum concentration of 1.1 mcg/mL and 5.9 mcg/mL when itraconazole was administered in daily doses of 200 mg and 400 mg, respectively 3.
Common questions
Can I take Itraconazole and Famotidine together?
Reduced itraconazole exposure and an increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Itraconazole and Famotidine 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 Itraconazole or Famotidine 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 (3)
- Product Information: SPORANOX(R) oral solution, itraconazole oral solution. Janssen Pharmaceuticals Inc (per FDA), Titusville, NJ, 2024. DailyMed
- Product Information: SPORANOX(R) oral capsules, itraconazole oral capsules. Janssen Pharmaceuticals Inc (per FDA), Titusville, NJ, 2024. DailyMed
- Patterson TF, Peters J, Levine SM, et al: Systemic availability of itraconazole in lung transplantation. Antimicrob Agents Chemother 1996; 40:2217-2220. PubMed
Keep reading about Itraconazole
Keep reading about Famotidine
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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