The risk of serious cardiac arrhythmias among cisapride users in the United Kingdom and Canada.
OBJECTIVE
Serious, although rare, ventricular arrhythmias and deaths have been reported in patients taking cisapride monohydrate. Without quantification of the risk involved, it is impossible to develop rational therapeutic guidelines.


METHODS
Arrhythmic events (sudden deaths and other events compatible with serious ventricular arrhythmias) were sought among 36,743 patients prescribed cisapride in the United Kingdom and Saskatchewan, Canada. Prescriptions and cases were identified from computerized medical claims data and physicians' office records. We compared rates of events between periods of recent cisapride use and nonrecent use, using cohort analysis. Potential confounding factors, including concomitant treatment with agents that inhibit CYP3A4 metabolism or that prolong the QT interval, were assessed in a nested case-control study.


RESULTS
In the cohort analysis, the incidence of the arrhythmic events was 1.6 times greater (95% confidence interval [CI]: 0.9 to 2.9) in periods of recent use. With adjustment for clinical history, use of CYP3A4 inhibitors, and use of drugs that prolong the QT interval, the odds ratio for cisapride and cardiac outcomes was 1.0 (95% CI: 0.3 to 3.7). There was no identifiable increase in risk when cisapride was dispensed at about the same time as QT-prolonging drugs or CYP3A4 inhibitors. QT-prolonging agents were associated with a 2.5-fold increase in the risk of arrhythmic events (95% CI: 1.1 to 5.8).


CONCLUSIONS
Serious rhythm disorders were not associated with cisapride use, although the upper confidence bounds do not rule out an increase in risk.
Walker
A M
AM
Epidemiology Resources, Inc., Newton Lower Falls, Massachusetts, USA.
Szneke
P
P
Weatherby
L B
LB
Dicker
L W
LW
Lanza
L L
LL
Loughlin
J E
JE
Yee
C L
CL
Dreyer
N A
NA
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000897:Anti-Ulcer Agents / Q000009:adverse effects*; D001145:Arrhythmias, Cardiac / Q000139:chemically induced*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D020117:Cisapride / Q000009:adverse effects*; D005260:Female; D005765:Gastrointestinal Agents / Q000009:adverse effects*; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012306:Risk; D012525:Saskatchewan / Q000453:epidemiology; D017678:Sex Distribution; D006113:United Kingdom / Q000453:epidemiology
D000897:Anti-Ulcer Agents; D005765:Gastrointestinal Agents; D020117:Cisapride