In the setting of auto-induction, what trough pattern would you expect over time?

• A. Increasing troughs
• B. Decreasing troughs
• C. Stable troughs
• D. No troughs

Answer: (B)

Auto-induction means the drug increases the activity of enzymes that metabolize it, typically hepatic enzymes. As you continue dosing, these enzymes are induced and clearance rises. With a constant dosing regimen, higher clearance pulls the trough concentrations (the lowest point just before the next dose) lower over time. After induction reaches its maximum, troughs level off at a new, lower value. So the trough pattern over time is decreasing as the drug’s own metabolism ramps up.