Variables
Description
What is this formula?
The two-compartment distribution model describes drug concentration after intravenous administration using two exponential phases.
The first term represents the rapid distribution phase, while the second term represents the slower terminal elimination phase.
When to use it
Use this formula when plasma concentration-time data show a biexponential decline after IV administration.
Example
Data:
A = 30 mg/L
B = 10 mg/L
alpha = 1.2 h⁻¹
beta = 0.15 h⁻¹
t = 3 h
Formula:
C = A·e^(-alpha·t) + B·e^(-beta·t)
Substitution:
C = 30·e^(-1.2×3) + 10·e^(-0.15×3)
Result:
C ≈ 6.68 mg/L
Applications
- Two-compartment pharmacokinetic modeling
- IV drug disposition analysis
- Distribution phase evaluation
- Terminal elimination assessment
- Pharmacokinetic simulation
Note
This is a biexponential pharmacokinetic model. The parameters A, B, alpha, and beta are usually estimated from concentration-time data. Only the main explicit concentration equation is included because solving for several variables would require nonlinear or iterative methods, which are not suitable for fCalc.