Combining citalopram (Celexa) with ciprofloxacin carries a risk of which cardiac change?

• A. Serotonin syndrome
• B. QT prolongation
• C. Hypertension
• D. Weight gain

Answer: (B)

The risk being tested is prolongation of the QT interval on the electrocardiogram due to drugs that affect the heart’s electrical repolarization. Citalopram can lengthen the QT interval, especially at higher doses, and ciprofloxacin can also prolong QT by blocking cardiac potassium channels that help reset the heart’s rhythm. Using them together can have additive effects, increasing the chance of a dangerous arrhythmia called torsades de pointes, which can progress to serious rhythm problems or sudden death.

This risk is more likely in people with electrolyte abnormalities (low potassium or magnesium), female sex, preexisting heart disease, bradycardia, or when higher doses are used. If this combination is necessary, monitor the QT interval and electrolytes, avoid other QT-prolonging drugs, and consider alternatives or dose adjustments.