Cardiotoxicity of cisapride may increase when this drug is associated with ranitidine.
Case report: A 37-day old term infant, treated with cisapride (1.2 mg/kg/d) and ranitidine for regurgitations, was hospitalized for malaise. A prolonged QT interval (with isolate ventricular extrasystoles), noted at admission, disappeared rapidly after cisapride withdrawal. Linkage to cisapride was probable, promoted by high dosage and cisapride metabolism inhibition by ranitidine, but its plasma concentration was not measured.
Conclusion: This case report stresses the problem of cisapride dosage in infants and the question of an interaction between cisapride and ranitidine.