Pick a scenario; every slider stays editable.
Educational model with made-up drug constants. It is not medical advice and not a tool for choosing a dose.
The science
Compartments. Gut dA0/dt = -kaA0; blood (central) dA1/dt = kaA0 - (k10+k12)A1 + k21A2; tissue (peripheral) dA2/dt = k12A1 - k21A2. Elimination rate constant k10 = CL/V, concentration C = A1/V. Each dose adds F * Dose to the gut at once; the equations are integrated with fourth-order Runge-Kutta (step 0.02 h).
One compartment (k12 = 0). One dose gives the Bateman curve C(t) = F D ka / (V (ka - k)) * (e-kt - e-kat) with half-life t1/2 = ln2 / k. The equations are linear, so repeated doses simply add (superposition).
Total exposure. AUC0-inf = F D / CL for a single dose, whatever the number of compartments. At steady state the average concentration is Cavg = F D / (CL tau), and the trough builds up by the accumulation factor R = 1/(1 - e-k tau) (one compartment, fast absorption).
Two compartments. Distribution into tissue makes a biphasic decline with rate constants alpha and beta, the roots of s2 - (k10+k12+k21)s + k10k21 = 0; the late slope is beta.
Therapeutic window. Below the minimum effective concentration (MEC) the drug does little; above the minimum toxic concentration (MTC) side effects grow. The page reports time in window and the peak and trough after the last dose.
Honest simplifications. First-order (linear) kinetics only, no saturable metabolism, no food effect, no lag time, no protein binding, constants that look typical but match no real drug, a single patient with no variability (real people differ 2-3 fold).