MajorFirst-generation antipsychotics. Butyrophenone derivatives×Other antidepressants (NaSSA)
Updated · Methodology
Mechanism
Mirtazapine prolongs QT dose-dependently, additively with haloperidol (especially parenteral). Plus combined sedation.
Symptoms
QT prolongation on ECG. Dizziness, syncope, palpitations. Severe cases: polymorphic ventricular tachycardia (torsades de pointes). Risk is higher with hypokalaemia and hypomagnesaemia.
Management
Avoid the combination with mirtazapine above 30 mg and parenteral haloperidol. At low doses and normal potassium, the combination is acceptable with ECG monitoring at 2 weeks. Alternative antipsychotics with minimal QT effect: olanzapine or aripiprazole.
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: Remeron (mirtazapine) prescribing information (2020)– ; DailyMed setid 98ad1917-a094-44f5-a28f-a64a8cfcd887
- AEMPS: Ficha técnica: Mirtazapina Cinfa 30 mg (nº registro 67068), secciones 4.5 y 4.7 (2026)– AEMPS, CIMA, nº registro 67068, revisión 06/2026, secciones 4.5 y 4.7