What drug was withdrawn from the market in 1997 and why?

• A. Rimonabant; due to suicidality
• B. Terfenadine; due to metabolism to Fexofenadine being inhibited by CYP3A4 inhibitors, causing QT prolongation and torsades de pointes
• C. Rofecoxib; due to cardiovascular risk
• D. Terbutaline; due to tachyphylaxis

Answer: (B)

This question tests how drug safety can hinge on drug–drug interactions that affect metabolism and lead to dangerous cardiac effects. Terfenadine was withdrawn from the market in 1997 because when its metabolism by CYP3A4 is inhibited (for example by certain antibiotics or antifungals), terfenadine accumulates in the body. This buildup can block cardiac potassium channels, prolong the QT interval, and trigger torsades de pointes, a potentially life‑threatening arrhythmia. After this risk was recognized, terfenadine was removed and later reintroduced in a safer form (fexofenadine) that doesn’t rely on the same metabolic pathway and has much less risk of QT prolongation. The other drugs had safety issues at different times or in different contexts, not the specific 1997 withdrawal for QT-related arrhythmias due to CYP3A4 inhibition.