Serious ventricular arrhythmias among users of cisapride and other QT‐prolonging agents in the United States

PURPOSE: To evaluate the risk of serious ventricular arrhythmia (SVA) with cisapride use in the United States. METHODS: The study population included 28,078 patients under the age of 65 years who received cisapride between 1993 and 1998 with no history of antiarrhythmia treatment. Each follow-up day was classified according to use of cisapride and other factors. Outcomes of SVAs were identified using medical claims records and National Death Index search, and confirmed by medical record review. Rates of events were calculated for time on and off cisapride. Poisson regression analysis was used to calculate adjusted rate ratios. RESULTS: There were 23 cases of SVAs; 10 during periods of cisapride use and 13 during periods of non-use. The adjusted rate ratio comparing SVA events in cisapride use time to non-use time was 1.60 (95% CI: 0.67-3.82), and that identified for the other QT-prolonging drugs was 1.60 (95% CI: 0.65-3.98). CONCLUSIONS: The evidence for an increased risk of SVAs associated with cisapride was equivocal after taking observation time on and off cisapride into account, and adjusting for risk factors, though we cannot exclude the possibility of a 3.8-fold increased risk. Overall, the plausible risks of cisapride were similar to those of other QT-prolonging drugs.