The withdrawal of Terfenadine from the market in 1997 was primarily due to drug interactions that inhibit its metabolism by which enzyme?

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Multiple Choice

The withdrawal of Terfenadine from the market in 1997 was primarily due to drug interactions that inhibit its metabolism by which enzyme?

Explanation:
Terfenadine was withdrawn because it relies on a liver enzyme, CYP3A4, to be metabolized into its active, safer form, fexofenadine. When CYP3A4 is inhibited by other drugs or substances, terfenadine levels rise in the blood. Elevated levels can prolong the QT interval and provoke dangerous ventricular arrhythmias, such as torsades de pointes. This dangerous interaction drove the withdrawal in 1997. The situation illustrates how inhibiting a specific metabolic enzyme can dramatically raise a drug’s risk profile, leading to market removal.

Terfenadine was withdrawn because it relies on a liver enzyme, CYP3A4, to be metabolized into its active, safer form, fexofenadine. When CYP3A4 is inhibited by other drugs or substances, terfenadine levels rise in the blood. Elevated levels can prolong the QT interval and provoke dangerous ventricular arrhythmias, such as torsades de pointes. This dangerous interaction drove the withdrawal in 1997. The situation illustrates how inhibiting a specific metabolic enzyme can dramatically raise a drug’s risk profile, leading to market removal.

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