Calculator
Mean Residence Time Calculator
The average time a drug molecule spends in the body before it is eliminated.
Mean residence time
34.56h
Estimated from half-life, assuming one-compartment IV bolus kinetics.
Calculation method
AUMC/AUC is preferred when you have the concentration–time data.
Valid only for a one-compartment drug given as an IV bolus.
Working
What AUMC means
Blue is the concentration curve C(t). Green is t × C(t) — AUMC is the area beneath it.
MRT = AUMC₀–∞ / AUC₀–∞
MRT = 1.44 × t½ (one-compartment IV bolus only)
AUC is the area under the concentration curve. AUMC is the area under the same curve after every point has been multiplied by its own time — the "first moment". Dividing one by the other gives a time-weighted average, which is exactly what a mean residence time is.
The 1.44 shortcut is 1/ln 2. It applies only when elimination is monoexponential from a single compartment after an IV bolus; for anything else, use AUMC/AUC.
References
- Gibaldi M, Perrier D. Pharmacokinetics. 2nd ed. New York: Marcel Dekker; 1982.
- Ducharme MP, Shargel L, editors. Shargel and Yu's Applied Biopharmaceutics & Pharmacokinetics. 8th ed. New York: McGraw Hill; 2022.
Common questions
Half-life is how long the concentration takes to halve. MRT is the average time an individual molecule spends in the body. For a simple one-compartment IV drug they are proportional (MRT = 1.44 × t½), but for a two-compartment or orally absorbed drug they diverge.
MRT is 1/k and half-life is ln 2 / k, so MRT / t½ = 1 / ln 2 = 1.4427. It only holds where a single exponential describes the whole curve.
Mean absorption time. After oral dosing, MRT_oral = MRT_iv + MAT, so subtracting the IV MRT from the oral MRT isolates how long absorption itself takes. It is one of the cleanest ways to compare formulations.
Because multiplying by t weights the late, low, noisy concentrations most heavily, and those are precisely the points measured least accurately. The extrapolated tail can contribute a large share of AUMC, so a small error in the terminal rate constant moves MRT a lot.
Vss = CL × MRT, where CL is Dose/AUC after an IV dose. Vss derived this way is model-independent, which is why it is preferred over the older Varea.
Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy