St. John's wort induces which hepatic enzyme, decreasing many drug levels?

St. John's wort induces which hepatic enzyme, decreasing many drug levels?

• A. CYP2D6
• B. CYP3A4
• C. UGT
• D. MAO

Answer: (B)

St. John's wort boosts the activity of a major liver enzyme that metabolizes many medications, which speeds up their breakdown and lowers their blood levels. The enzyme most affected is CYP3A4. Induction occurs by increasing CYP3A4 gene transcription in liver cells, leading to faster clearance of drugs that are substrates of this enzyme. Clinically, this can reduce the effectiveness of drugs with narrow therapeutic ranges or those heavily dependent on CYP3A4 for clearance, such as certain oral contraceptives, immunosuppressants, some statins, and antiretrovirals. Induction develops over days to weeks and gradually reverses after the herb is stopped. There may also be an effect on P-glycoprotein, which can further reduce drug absorption for some medications. In short, the hepatic enzyme induced by St. John’s wort is CYP3A4.

St. John's wort boosts the activity of a major liver enzyme that metabolizes many medications, which speeds up their breakdown and lowers their blood levels. The enzyme most affected is CYP3A4. Induction occurs by increasing CYP3A4 gene transcription in liver cells, leading to faster clearance of drugs that are substrates of this enzyme. Clinically, this can reduce the effectiveness of drugs with narrow therapeutic ranges or those heavily dependent on CYP3A4 for clearance, such as certain oral contraceptives, immunosuppressants, some statins, and antiretrovirals. Induction develops over days to weeks and gradually reverses after the herb is stopped. There may also be an effect on P-glycoprotein, which can further reduce drug absorption for some medications. In short, the hepatic enzyme induced by St. John’s wort is CYP3A4.