Pimozide is contraindicated with any other QT-prolonging drug, and citalopram raised its QTc by about 10 milliseconds
The pimozide label contraindicates it "in patients taking other drugs which prolong the QT interval" and with CYP3A4 inhibitors; one 2 mg dose with citalopram 40 mg gave "a mean increase in QTc values of approximately 10 msec."
Reasonable evidence with real limitations. how we score evidence
Caveat on this rating: The 10 msec figure is from a single-dose volunteer study cited in the label, not from patients on chronic pimozide.
Pimozide is a niche antipsychotic, used for Tourette's, but its label is the clearest example in psychiatry of an interaction written as an absolute bar.
Significant findings
Pimozide tablets prescribing information (Par, September 2026), Contraindications: "Because pimozide prolongs the QT interval of the electrocardiogram it is contraindicated in patients with congenital long QT syndrome, patients with a history of cardiac arrhythmias, patients taking other drugs which prolong the QT interval of the electrocardiogram or patients with known hypokalemia or hypomagnesemia".
The Drug Interactions section lists the partners: "pimozide should not be given with dofetilide, sotalol, quinidine, other Class Ia and III anti-arrhythmics, mesoridazine, thioridazine, chlorpromazine, droperidol, sparfloxacin, gatifloxacin, moxifloxacin, halofantrine, mefloquine, pentamidine, arsenic trioxide, levomethadyl acetate, dolasetron mesylate, probucol, tacrolimus, ziprasidone, or other drugs that have demonstrated QT prolongation as one of their pharmacodynamic effects." Macrolide antibiotics are named separately.
On metabolism: "Since pimozide is partly metabolized via CYP 3A4, it should not be administered concomitantly with inhibitors of this metabolic system, such as azole antifungal agents and protease inhibitor drugs". And the one measured interaction with an antidepressant: "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" alone.
Worth asking
Ten milliseconds is the number that made the citalopram, escitalopram, sertraline, paroxetine and fluvoxamine labels contraindicate pimozide. If you or a child takes pimozide, every new prescription, including an antibiotic, an antifungal or an antidepressant, is a question for the pharmacist first. The label also names grapefruit's mechanism, CYP3A4, and the Bailey 2013 row in this wave lists pimozide among the grapefruit interactions.
Source
Pimozide tablets: FDA-approved prescribing information, Contraindications and Drug Interactions — Par Health USA, LLC; US Food and Drug Administration (2026)
Regulator or national health body
How this was scored
- Study design
- Regulatory safety determination
- Funding
- Industry funded
- Published in
- Regulator or national health body
- Sample size
- not recorded
- Preregistered
- not recorded
- Conflicts disclosed
- not recorded
- Independent of proponent
- not recorded
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published September 21, 2026.
Questions
How strong is the evidence behind this?
veisund rates this source "moderate evidence". Reasonable evidence with real limitations. It scores 57 out of 100 on our published rubric. One caveat travels with that badge: The 10 msec figure is from a single-dose volunteer study cited in the label, not from patients on chronic pimozide. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
Pimozide tablets: FDA-approved prescribing information, Contraindications and Drug Interactions — Par Health USA, LLC; US Food and Drug Administration (2026). Published in: Regulator or national health body. The full source is linked on this page so you can read it yourself.
Who paid for this research, and does that matter?
Study design: Regulatory safety determination. Funding: Industry funded. Independence from the proponent is not recorded. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.