Example: A patient received a single dose of 500 mg erythromycin in the form of a tablet that is known to have 80% bioavailability.

Calculate the time to reach the maximum concentration and the maximum erythromycin concentration after this single dose if k is 0.2 hr-1, ka is 1.3 hr-1, and Vd is 40 liters.

tmax =

In ka - In k

ka - k
Cpmax =

F D ka

Vd (ka - k) (e -k tmax - e-ka tmax)
tmax =

In 1.3-In 0.2

(1.3 - 0.2)hr-1 =1.7hr
Cpmax =

(0.8) 500mg 1.3hr-1

40L (1.3 - 0.2)hr-1 (e-0.2hr-1(1.7hr) -e1.3hr-1(1.7hr)) =7.115 mg/L

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