How Drugs Move — Walkelia Fabián

Parameters · Dosing

Dose D 400 mg

Amount administered with each modeled dose

Bioavailability F 80%

Fraction that reaches systemic circulation

Apparent volume of distribution Vd 30 L

Relates amount in the body to measured plasma concentration

Clearance CL 5.2 L/hr

Apparent volume of plasma cleared per unit time

Absorption rate k_a 2.0 /hr

Speed of absorption from the GI tract

Dosing interval τ 8 hr

How often the dose is repeated

Concentration–Time Curve

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C_max

µg/mL · peak concentration

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T_max

time to peak

—

t½ derived

from Vd and CL

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AUC

µg·h/mL · displayed interval

Tutor annotation

Choose a parameter, predict the direction of change, then test it.

Reading the curve

C_max is the peak — the highest concentration the body reaches after one dose.

T_max is when the curve peaks — absorption rate vs. elimination rate.

Yellow band is a fictional reference range for comparing model outputs. It is not a dosing recommendation.

AUC represents total modeled systemic exposure over the displayed interval.

This educational simulation uses a one-compartment oral model with first-order absorption and elimination: C(t) = (F·D·k_a) / (Vd·(k_a−k_e)) · (e^−k_et − e^−k_at), where k_e = CL/Vd and t½ = 0.693·Vd/CL. Scenarios and reference bands are fictional. Clinical interpretation requires drug-specific exposure–response evidence, patient characteristics and established dosing guidance.

Walkelia Fabián