Example : Quinidine sulfate is a class Ia antiarrhythmic drug. Its average total body clearance in adults is 0.22 L/hr/kg while in older patients (>70 years) the average total body clearance is 0.15 L/hr/kg. What is the steady state conc of quinidine achieved after administration of the average dose ( 5 mg/kg q 6 hr) to adults and to older patients ? What is the quinidine dose required to achieve quinidine steady state conc of 3 mg/L in older patients ? (F = 0.8)
Population
The steady state quinidine
conc is higher in older
patients since they have
lower total body clearance.
Cpaverage =
(0.8) 5 mg/kg
0.22 L/hr/kg 6hr
= 3.03 mg/L
Cpaverage =
(0.8) 5 mg/kg
0.15 L/hr/kg 6hr
= 4.44 mg/L
The dose required to achieve a steady state conc of 3 mg/L in geriatric patients
3 mg/L=
(0.8) Dose
0.15 L/hr/kg 6hr
Dose = 3.38 mg/kg
