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Volume of Distribution

VD and Loading Dose

This page shows that the Vd determines the initial drug concentration in the plasma, after distribution. Drag the slider and watch the graph.

Drugs with a small Vd have a high initial concentration and drugs with a large Vd have a low concentration.

It follows that to achieve a target initial concentration, a loading dose (LD) is required to fill up Vd, i.e at time 0.

LD = Ab

LD = Vd x Cp


Log Cp (mg/L)

Time (hours)


Amount in body =
Vd x plasma concentration

Ab = Vd x Cp

Vd = Ab / Cp

5 L 10,000 L