Example:

A patient is taking 600 mg procainamide every 6 hours for the treatment of cardiac arrhythmia. His average procainamide plasma conc at s.s. is 4.0 mg/L. What will be the dose required to increase the average plasma procainamide conc at s.s to 6 mg/L?
(F=1, k=0.231hr-1 and Vd =110L)

Dose (mg)
The average s.s. concentration is
proportional to the administered
dose. The dose should be
increased by 50%.

Answer:

Cpaverage ss=

F D

k Vd τ
6 mg/L =

(1) D

0.231hr- 1 x 110L x 6hr
Dose = 900mg every 6hr

The dose should be increased by 50% to achieve steady state conc of 6 mg/L.

Dose (mg)