Example : A beta blocker has a biological half life of 3 hr, Vd of 20 L, and MEC of 2 mg/L. What is the duration of effect after administration of a single iv dose of 200 mg of this drug ? and what is the iv dose required to produce therapeutic effect for a period of 6 hr ?
MEC
Duration of effect
The duration of effect is the time
required for the drag conc to
decline to the MEC (2 mg/L).
MEC
The dose should achieve
initial drug conc that will
decline to 2 mg/L after 6 hr.
The duration of effect is the time required for the drug conc to decline to 2 mg/L
2 mg/L =
200 mg
20 L
e -0.231 (t)
t = 7 hr Duration = 7 hr
The dose that will achieve drug conc of 2 mg/L after 6hr :
2 mg/L =
Dose
20 L
e -0.231 (6hr)
Dose = 160 mg
