MajorFluoroquinolone antibacterials×First-generation antipsychotics. Butyrophenone derivatives
Updated · Methodology
Mechanism
Dual mechanism: both prolong QT (additively), and ciprofloxacin blocks CYP1A2 – a partial haloperidol clearance route. Haloperidol levels rise.
Symptoms
QT prolongation on ECG. Clinically: dizziness, syncope, palpitations. Severe cases progress to polymorphic ventricular tachycardia (torsades de pointes) with risk of ventricular fibrillation and sudden cardiac death. Risk is higher with hypokalaemia, hypomagnesaemia, bradycardia, and ischaemic heart disease.
Management
Avoid the combination. Alternative antibiotics: a cephalosporin or nitrofurantoin. 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: Haloperidol tablet (Ajanta Pharma USA Inc.) – Prescribing Information (2020)– ; DailyMed setid 31e33656-2f53-49e6-9816-261ea2e6961a
- AEMPS: Ficha técnica: Ciprofloxacino (nº registro 62765), sección 4.5 (2025)– AEMPS, CIMA, nº registro 62765, revisión 11/2025, sección 4.5