Theophylline plasma concentrations determined 2 and 8 hours after administration of a single iv bolus dose. were 16 and 8 mg/L, respectively. Calculate theophylline half life in this patient.
You can determine theophylline half life graphically or you can calculate it mathematically
Cp1 = 16 mg/L
Cp2 = 8 mg/L
6 hr
The y-intercept is 20 mg/L. It took 6 hours for the conc. to decide to 10 mg/L
Cp8 hr = Cp2 hr e -k(8-2)hr
8mg/L = 16mg/L e -k(8-2)hr
ln 2 = k(6hr)
k = 0.1155 hr-1
t1/2 = 0.693
k= 0.693
0.1155 hr-1 = 6hr
