Metronidazole and Pimozide: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Pimozide
No brand names on recordMetronidazole
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 QT interval prolongation
Interaction Deep Dive
The concomitant use of pimozide with drugs that cause QT interval prolongation is contraindicated, as coadministration may increase the risk of QT interval prolongation and serious ventricular arrhythmias. It is also contraindicated in patients treated with other drugs which prolong the QT interval of the echocardiogram or patients with known hypokalemia or hypomagnesemia1.
Why it happens (mechanism)
Additive QT interval prolongation
Literature reports
4 reports — tap to read
a) In a controlled study, a single dose of pimozide 2 mg coadministered with racemic citalopram 40 mg given once daily for 11 days was associated with a mean increase in QTc values of approximately 10 msec compared to pimozide given alone. Racemic citalopram did not alter the mean AUC or Cmax of pimozide. The mechanism of this pharmacodynamic interaction is not known 1.
b) Case-control studies demonstrated an association of serious ventricular arrhythmias and sudden cardiac death, particularly with domperidone doses greater than 30 mg/day and use of domperidone in patients older than 60 years 2.
c) In experimental studies of conditions other than Tourette's Disorder, sudden, unexpected deaths have occurred in patients receiving pimozide in the range of 1 mg per kg. One possible mechanism for such deaths is prolongation of the QT interval predisposing patients to ventricular arrhythmia. Perform an electrocardiogram before pimozide treatment is initiated and periodically thereafter, especially during the period of dose adjustment 1.
d) Sultopride may induce prolongation of the QT interval and ventricular arrhythmias including torsades de pointes following therapeutic or toxic doses 345.
Common questions
Can I take Metronidazole and Pimozide together?
An increased risk of QT interval prolongation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Metronidazole and Pimozide 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 "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Metronidazole or Pimozide 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 (5)
- Product Information: Pimozide oral tablet, pimozide oral tablet. Endo USA, Inc (per DailyMed), Malvern, PA, 2017. DailyMed
- Teva Canada Limited: Dear Healthcare Professional letter for domperidone maleate. Teva Canada Limited. Toronto, Canada. 2012.
- Lande G, Drouin E, Gauthier C, et al: Arrhythmogenic effects of sultopride chlorhydrate: clinical and cellular electrophysiological correlation. Ann Fr Anesth Reanim 1992; 11:629-635.
- Montaz L, Varache N, Harry P, et al: Torsades de pointes during sultopride poisoning. J Toxicol Clin Exp 1992; 12:481-496.
- Harry P: Acute poisoning by new psychotropic drugs. Rev Prat 1997; 47:731-735.
Keep reading about Pimozide
Keep reading about Metronidazole
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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