St. John's wort induces which enzyme family?

• A. Cytochrome P450 enzymes
• B. Cholinesterase enzymes
• C. Kinases
• D. Transpeptidases

Answer: (A)

St. John’s wort works by increasing the activity of drug-metabolizing enzymes, specifically the cytochrome P450 family. Its active components, notably hyperforin, activate the pregnane X receptor (PXR), which boosts the production of CYP enzymes, especially CYP3A4. When these enzymes are upregulated, many drugs are metabolized more quickly, lowering their blood levels and potentially reducing clinical effect or leading to treatment failure.

This is especially important in older adults who often take multiple medications. Enhanced metabolism can make anticoagulants, immunosuppressants, certain antiepileptics, oral contraceptives, and various other drugs less effective. The induction doesn't happen immediately; it develops over days to weeks and can persist after stopping, gradually returning to baseline.

The other enzyme families listed—cholinesterase enzymes, kinases, and transpeptidases—aren’t the clinically relevant targets of St. John’s wort’s inducing effect. The herb’s significant drug interaction risk centers on the cytochrome P450 system, particularly CYP3A4.