After intake, a substance is absorbed into the bloodstream faster than the body eliminates it, so blood concentration rises to a peak and then falls off roughly exponentially. This simulator uses the classic two-phase (Bateman) pharmacokinetic curve — a fast absorption phase governed by rate ka, followed by a slower first-order elimination phase governed by rate ke, which is what a real toxicology screen has to account for when interpreting a result.
C(t) = Dose·ka / (Vd·(ka−ke)) · (e^(−ke·t) − e^(−ka·t))
elimination phase (t large): C(t) ≈ C0·e^(−ke·t)
half-life: t½ = ln(2) / ke
- Substance A/B/C — three illustrative half-lives (short, medium, long). A short half-life clears fast and gives a narrow window in which a sample will still test positive; a long half-life stays detectable for days.
- Dose — scales peak concentration (Cmax) roughly linearly; it does not change the shape or timing of the curve, only its height.
- Sample time — when in the timeline the "blood draw" is taken. Move it (or click the timeline in the 3D view) to see how the measured concentration — and whether it clears the detection threshold — depends entirely on timing.
- Detection window — the interval during which concentration stays above the assay's detection threshold (dashed red plane). Outside that window, a real sample would come back negative even though the substance was taken — the central lesson of forensic toxicokinetics.
This is an educational model with arbitrary units, not a reference for any real drug or poison — the goal is to show why sample timing, not just substance identity, determines a toxicology result.