My Easy Science
Drug Interaction Visualiser
A CYP inhibitor or inducer changes clearance. See the curve, the AUC and the peak move.
Set the drug and the interaction, then tap Show the interaction.
For learning only. Not for patient care decisions. Always check with a qualified professional and the product label.
Before and with the interaction
| Value | Result | ||
|---|---|---|---|
| Clearance ratio (new / old) | — | ||
| Half-life before (h) | — | ||
| Half-life with interaction (h) | — | ||
| AUC before (mg·h/L) | — | ||
| AUC with interaction (mg·h/L) | — | ||
| AUC ratio | — | ||
| Steady-state average concentration before (mg/L) | — | ||
| Steady-state average concentration with interaction (mg/L) | — | ||
| Steady-state concentration change (%) | — | ||
| Peak before (mg/L) | — | ||
| Peak with interaction (mg/L) | — | ||
Curve data
Show data
| Time (h) | Baseline | With interaction |
|---|---|---|
| Tap Show the interaction to see the numbers. | ||
Values from the drawn curves.
Starting values
Worked example: an inhibitor with fm 0.8 and [I]/Ki 4 gives CL new / CL = 0.8/5 + 0.2 = 0.36, so the AUC ratio is 1 / 0.36 = 2.78, about 178% higher exposure.
How it works
Checked against three hand-worked examples (see the page source comments).
Results are shown to 2 decimal places (the clearance ratio to 3).
Most drugs are cleared by CYP enzymes in the liver, but usually only part of the clearance goes through one enzyme. That share is fm, the fraction cleared by that enzyme. An inhibitor blocks the enzyme, so only the fm part of the clearance falls: CL new / CL = fm / (1 + [I]/Ki) + (1 − fm). An inducer makes more enzyme, so the fm part grows: CL new / CL = fm × (1 + induction) + (1 − fm), where the induction number is the added fold change, so 2 means three-fold activity. Because AUC equals dose / clearance, the AUC ratio is the old clearance divided by the new one, and the half-life moves by the same ratio when Vd is unchanged.
Worked examples, all checked: an inhibitor with fm 0.8 and [I]/Ki 4 gives CL new / CL = 0.8/5 + 0.2 = 0.36, so the AUC ratio is 1 / 0.36 = 2.78, about 178% higher exposure. An inducer with fm 0.8 and induction 2 gives CL new / CL = 0.8 × 3 + 0.2 = 2.6, so the AUC ratio is 1 / 2.6 = 0.38, about 62% lower exposure. And if fm is 0, the drug is not cleared by that enzyme at all, so the AUC ratio is 1.00 whatever the strength. That is why the same inhibitor can matter a lot for one drug and barely at all for another.
The steady-state average concentration moves with the AUC ratio, so a 2.78× AUC means the average level at steady state is also about 2.78× higher. The peak moves less than the AUC for an oral drug, because absorption still limits how fast the level can climb, and for an IV bolus the first-dose peak does not change at all. This tool shows the shape of the change; real decisions need the real drug, its therapeutic range, and a clinician.