In Vitro CYP Inhibition Screen (ICH M12 Basic Methods)
ICH M12 basic in vitro screen for CYP inhibition: Cmax,u/Ki,u under 0.02, the gut CYP3A test under 10, or the time-dependent ratio under 1.25 excludes the risk.
Open the tool → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Mechanism
- Time-dependent inhibition
- Concentration unit
- µM
- Cmax,u directly
- 0.1
- KI,u
- 1
- kinact
- 0.05
- Enzyme for Table 6 kdeg
- CYP3A4 (hepatic)
Result: (kobs + kdeg) / kdeg = 53.08, not below 1.25
The tool opens with these values already filled in. Replace them with your own.
What you enter
- Mechanism
- Concentration unit
- Molecular weight (g/mol)
- Cmax at steady state (total)
- fu,p
- fu,p below 1% shown reliable
- Cmax,u directly
- Ki,u
The other 5 fields
- Maximum clinical dose (mg)
- KI,u (time-dependent)
- kinact (per minute)
- Enzyme for Table 6 kdeg
- kdeg (per minute)
How this is calculated
Citation
ICH M12 Guideline, Drug Interaction Studies (Step 4, May 21, 2024), sections 2.1.2.1 and 2.1.2.2: basic methods for reversible, intestinal CYP3A and time-dependent inhibition, the 1% fu,p default, and Table 6 kdeg. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.