Why was cisapride withdrawn from the US market?

• A. Caused severe constipation
• B. Caused cardiac dysrhythmias
• C. Caused liver failure
• D. Caused pancreatitis

Answer: (B)

Drug-induced QT prolongation leading to potentially fatal ventricular arrhythmias explains why cisapride was withdrawn. Cisapride is a prokinetic that can affect cardiac repolarization by prolonging the QT interval, increasing the risk of torsades de pointes. This risk is higher when cisapride levels are increased by drug interactions (notably CYP3A4 inhibitors) or by electrolyte disturbances. As reports of serious cardiac events grew, the FDA removed cisapride from the U.S. market to prevent further harm. The other listed adverse effects (constipation, liver failure, pancreatitis) were not the driving reason for the withdrawal.