The drug-action atlas

Enter through a molecule, a synapse, or a brain circuit. Change the conditions and trace what happens next.

All learning models

Explore the system

How much remains?

Change amount, half-life, and elapsed time. Compare a constant fractional loss with a constant absolute loss.

How much remains?

Diagram zoom

Amount remaining (model units)

Mechanism and exceptions

Half-life (hours)
Time (hours)	Amount remaining (model units)
0	60
5,3	23,81
10,7	9,45
16	3,75
21,3	1,49
26,7	0,59
32	0,23

Amount remaining (model units): 30

First order: constant fraction per time. Zero order: constant amount per time; ethanol is the course example. These models omit absorption, redistribution, and individual metabolism.

Starting amount / amount per dose60Half-life (hours)4Elapsed time (hours)4Zero-order comparison

Model units; no clinical dose or treatment prediction.

Animate the diagram

On a small screen, pan the diagram or increase zoom. Named controls provide the same exploration by keyboard.

Sources and model limits

Original schematic. Positions show relationships; structures and concentrations are not to scale.

Julien's Primer of Drug Action · 15 · 1 · How much remains? · PDF 18, 19 · 1.10

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The drug-action atlas

Enter through a molecule, a synapse, or a brain circuit. Change the conditions and trace what happens next.

All learning models

Explore the system

How much remains?

Change amount, half-life, and elapsed time. Compare a constant fractional loss with a constant absolute loss.

How much remains?

Diagram zoom

Amount remaining (model units)

Mechanism and exceptions

Half-life (hours)
Time (hours)	Amount remaining (model units)
0	60
5,3	23,81
10,7	9,45
16	3,75
21,3	1,49
26,7	0,59
32	0,23

Amount remaining (model units): 30

First order: constant fraction per time. Zero order: constant amount per time; ethanol is the course example. These models omit absorption, redistribution, and individual metabolism.

Starting amount / amount per dose60Half-life (hours)4Elapsed time (hours)4Zero-order comparison

Model units; no clinical dose or treatment prediction.

Animate the diagram

On a small screen, pan the diagram or increase zoom. Named controls provide the same exploration by keyboard.

Sources and model limits

Original schematic. Positions show relationships; structures and concentrations are not to scale.

Julien's Primer of Drug Action · 15 · 1 · How much remains? · PDF 18, 19 · 1.10