Major
Ciprofloxacin × citalopram
Fluoroquinolone antibacterials×SSRI (selective serotonin reuptake inhibitor)
Mechanism
Additive QT prolongation (both prolong QT). Ciprofloxacin weakly blocks CYP1A2; citalopram is metabolised by CYP2C19, so the pharmacokinetic effect is minimal. The main risk is additive QT.
Symptoms
QT prolongation on ECG. Clinically: dizziness, syncope, palpitations. Severe cases progress to polymorphic ventricular tachycardia (torsades de pointes). Risk is higher with hypokalaemia, hypomagnesaemia, bradycardia, and ischaemic heart disease.
Management
Alternative antibiotics: a cephalosporin or nitrofurantoin (no QT effect). If ciprofloxacin is needed: ECG before start, maintain potassium and magnesium, keep citalopram at 20 mg.
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.