## Clearance

## Total volume of plasma from which drug is completely removed per unit of time (units = ml/min). May be viewed as a proportionality constant that relates the rate of elimination to C

_{p}.## Rate of Elimination = Cl C

_{p}(1)## Rate of Elimination = (dq

_{T}/dt) = q_{T}k_{e}(2)## Cl C

_{p}= q_{T}k_{e }(3)## Cl = (q

_{T}k_{e})/C_{p}= V_{d}k_{e}(4)## Cl = Dose/AUC

(AUC is area under plasma concentration vs. time curve )

Drug

Variable

A

BClearance, ml/min1500 100

Rate of elimination, µg/min15

500 Volume of distribution, liter20

0.7

Plasma concentration, mg/liter0.01

5

This table shows that a rapidly cleared drug (A) can be eliminated slowly if the C

_{p}is low. Drug B is rapidly eliminated even though the clearance is low because the V_{d }is small and the C_{p}correspondingly high.

B.7c-1