Rifampin exerts its effect by which mechanism, and what is a major consequence for drug interactions?

• A. Inhibits bacterial DNA-dependent RNA polymerase; induces hepatic enzymes causing drug interactions
• B. Inhibits cell wall synthesis and increases drug susceptibility
• C. Disrupts RNA polymerase without affecting metabolism
• D. Inhibits folate synthesis in bacteria

Answer: (A)

Rifampin works by binding to the bacterial DNA-dependent RNA polymerase and blocking transcription, which is how it stops bacterial growth. A major consequence for drug interactions is that rifampin strongly induces hepatic cytochrome P450 enzymes, speeding up the metabolism of many other drugs. This leads to lower blood levels and potentially reduced efficacy of coadministered medications, sometimes requiring dose adjustments or avoidance of certain combinations. In addition to the antibacterial action, this enzyme induction is the key reason rifampin has so many drug interactions.