Quetiapine and Ketoconazole Topical: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Quetiapine
Ketoconazole Topical
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 QUEtiapine exposure and an increased risk of QT interval prolongation
Interaction Deep Dive
Coadministration of ketoconazole (a strong CYP3A4 inhibitor that may prolong the QT interval) with CYP3A4 substrates that are known to prolong the QT interval, such as QUEtiapine is contraindicated1. Concomitant use may increase QUEtiapine exposure and additionally may result in additive effects on the QT interval prolongation. If coadministration cannot be avoided, the dose of QUEtiapine may need to be reduced to one-sixth of the original dose. When ketoconazole is discontinued, subsequently increase QUEtiapine dose to 6-fold 23. Concomitant use may result in life-threatening ventricular tachyarrhythmias such as torsade de pointes 1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of QUEtiapine; additive QT interval prolongation
Literature reports
2 reports — tap to read
a) In drug interaction studies, the coadministration of a potent CYP3A4 inhibitor, ketoconazole 200 mg once daily for 4 days, and a single dose of QUEtiapine 25 mg resulted in an 84% decrease in QUEtiapine clearance and a 6.2-fold increase in QUEtiapine AUC 23.
b) A 32-year-old man with schizoaffective disorder and metabolic syndrome experienced a significant increase in QUEtiapine plasma concentration following administration of clarithromycin. The patient, hospitalized for acute psychotic symptoms, was treated with 50 mg QUEtiapine daily with a gradual increase in dosage to 700 mg over 10 days. Psychotic symptoms dissipated within 3 weeks. On day 28, the patient developed a lower respiratory infection and was treated with oral sultamicillin 750 mg and clarithromycin 500 mg along with his evening dose of QUEtiapine 400 mg. The following morning, 750 mg sultamicillin, 500 mg clarithromycin, and 300 mg QUEtiapine were given. Within hours the patient became somnolent, and plasma QUEtiapine levels were 826.8 mcg/L (normal range, 70 to 170 mcg/L). The patient developed severely impaired consciousness and respiratory depression. QUEtiapine overdose was suspected and treatment was discontinued. Plasma levels were continually measured over the course of 1 week until complete recovery was achieved 4.
Common questions
Can I take Quetiapine and Ketoconazole Topical together?
Increased QUEtiapine exposure and an increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Quetiapine and Ketoconazole Topical interaction?
It is rated contraindicated. These should generally not be used together.
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.
Questions for your pharmacist
- Does my dose of Quetiapine or Ketoconazole Topical 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: Ketoconazole oral tablet, ketoconazole oral tablet. Taro Pharmaceuticals U.S.A. Inc. (per DailyMed), Hawthorne, NY, 2024. DailyMed
- Product Information: SEROQUEL(R) oral tablets, quetiapine oral tablets. AstraZeneca Pharmaceuticals LP (per FDA), Wilmington, DE, 2020. DailyMed
- Product Information: SEROQUEL XR(R) oral extended-release tablets, quetiapine oral extended-release tablets. AstraZeneca Pharmaceuticals LP (per FDA), Wilmington, DE, 2022. DailyMed
- Schulz-Du Bois C, Schulz-Du Bois AC, Bewig B, et al: Major increase of quetiapine steady-state plasma concentration following co-administration of clarithromycin: confirmation of the pharmacokinetic interaction potential of quetiapine. Pharmacopsychiatry 2008; 41(6):258-259. PubMed
Keep reading about Quetiapine
Keep reading about Ketoconazole Topical
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