PHA 5127
Homework #1
(Total: 10 points)
#1) Calculate AUC0
Æ
∞ from the given concentration-time profile. (3 points)
Time (h) Plasma concentration (mg/L)
1 94.8
4 80.1
6 70.3
8 59.9
12 40.1
We first need to determine whether the drug is eliminated in a first or a zero-order
elimination process. An easy way to approach this question is to graph the data.
y = -4.9831x + 99.935
R2 = 0.9999
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02468101214
Time (h)
Plasma concentration (mg/L)
Plasma concentration and time show a linear relationship on a normal scale. Therefore,
drug is eliminated in a zero-order process. (First-order process would show a linear
relationship on a semi-log scale!) Æ Equal amounts of drug are eliminated per hour. In
order to determine AUC0Æ∞ we need to calculate t(0 hours) and the time when the plasma
concentration reaches zero. Looking at the data set, we see that the plasma concentration
decreases by approximately 5mg/L per hour. Thus, the plasma concentration will be
about 100mg/L at time zero and approach zero after about 20 hours.
Now let’s calculate the areas of the individual trapezoids according to:
)(
212
12 tt
CC −•
+
Time (h) Plasma concentration (mg/L) AUCs (mg*h)/L
0 100
1 94.8 97.4
4 80.1 262.35
6 70.3 150.4
8 59.9 130.2
12 40.1 200
20 0 160.4
SUM 1000.75
1
