CriticalSSRI (selective serotonin reuptake inhibitor)×5-HT3 serotonin receptor antagonist
Updated · Methodology
Mechanism
Ondansetron prolongs QT in a dose-dependent way, as its SmPC states, and the same label describes serotonin syndrome when it is given with SSRIs. The citalopram SmPC lists ongoing treatment with any drug capable of prolonging the QT interval among its contraindications, with no exceptions.
Symptoms
QTc prolongation on ECG, palpitations, dizziness, syncope, with torsade at the far end. Serotonin syndrome is tracked separately: agitation, confusion, tremor, myoclonus, sweating, hyperthermia. Arrhythmia risk is higher with hypokalaemia, hypomagnesaemia and bradycardia.
Management
The pair sits in the citalopram SmPC contraindications, so the question is which drug stays, not how far to cut the dose. A single intravenous dose is capped at 16 mg in the label precisely because of QT. Post-operative and chemotherapy nausea have antiemetics outside the setron group, and on citalopram those are the ones chosen.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- FDA: FDA Drug Safety Communication on citalopram QT prolongation (2012)
- AEMPS: Ficha técnica de Seropram 30 mg (citalopram) (2024)– AEMPS CIMA, nregistro 63564, revisión 01/2024, secciones 4.2, 4.3 y 4.4
- AEMPS: Ficha técnica de Zofran 4 mg comprimidos (ondansetrón) (2024)– AEMPS CIMA, nregistro 59069, revisión 05/2024, secciones 4.4 y 4.5