Week 3 AUC Flashcards
toxicology
AUC can be used as a measure of drug exposure. It is derived from drug concentration and duration.
biopharmaceuticals
The AUC is an important parameter in the comparison of drug products. Bioequivalency (for generics) or bioavailability studies can be analyzed by comparing AUC values
pharmacokinetics
AUC values can be used to determine other pharmacokinetic parameters, such as C0, V, CL, or bioavailability, F
analytical method
for a drug following first-order elimination from a single compartment after an IV bolus, the AUC is
auc = Co/k
Trapezoidal Method - One segment
area = C1 + C2/2 x (t2-t1)
Trapezoidal Method - add it all up
auc = C1 + C2/2 x (t2-t1) + C2+ C3/2 x (t3-t2) + …Cn/k
what do you do before and after your first time point?
AUC - 0 to 1st data point
After a rapid IV bolus, can be calculated after determining C0 by extrapolation.
AUC = (C0 + C1)/2 x t1
Total clearance equation for intravenous dose
CL = dose/AUC
Total clearance equation for extravascular dose
CL/F = dose/AUC ***** very important
for drugs that are eliminated by a first-order
process, AUC is directly proportional to the dose
(linear pharmacokinetics).
in these cases, CL does not depend on dose; therefore:
AUC1/AUC2 = dose1/dose2
F
percentage of the dose absorbed
- ratio of the AUC for extravascular dose (IM, PO, SC, etc) relative to an (IV) dose
- F can be calculated from AUC, based on the assumption that CL (or k) remains constant
F = AUC po/Dosepo x Doseiv/AUCiv
Levothyroxine
• Doses are the same for PO and IV
• for both IV and PO, 97% of AUC occurred after last timepoint!
F = 68%. they were able to absorb 68% of levothyroxine
AUC
– a measure of exposure
– a direct way to estimate CL
– a way to quantify the bioavailability
what is trapezoid method for?
calculating AUC
trapezoidal Method – the End
- If we assume the last data points continue to follow a mono- exponential decay, the area after the last time point can be estimated:
AUC n - infinity = Cn/k
