Area Under the Curve (Pharmacokinetics)
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The area under the curve (AUC) represents the total drug exposure over time and is calculated from the concentration of a drug in blood plasma plotted over time. The AUC is useful for determining if two formulations deliver the same dose and for monitoring toxic drugs. It can indicate the average concentration over an interval and is referenced when discussing drug elimination from the body.
![Area under the curve (pharmacokinetics)
In the field of pharmacokinetics, the area under the
curve (AUC) is the area under the curve (mathematically
known as definite integral) in a plot of concentration of
drug in blood plasma against time. Typically, the area
is computed starting at the time the drug is administered
and ending when the concentration in plasma is negligi-
ble. In practice, the drug concentration is measured at
certain discrete points in time and the trapezoidal rule is
used to estimate AUC.
1 Interpretation and usefulness of
AUC values
The AUC (from zero to infinity) represents the total drug
exposure over time. Assuming linear pharmacodynamics
with elimination rate constant K, one can show that AUC
is proportional to the total amount of drug absorbed by
the body. The proportionality constant is 1/K.
This is useful when trying to determine whether two for-
mulations of the same dose (for example a capsule and
a tablet) release the same dose of drug to the body. An-
other use is in the therapeutic monitoring of toxic drugs.
For example, gentamicin is an antibiotic which displays
nephro- and ototoxicities; measurement of gentamicin
concentrations in a patient’s plasma and calculation of the
AUC is used to guide the dosage of this drug.
AUC becomes useful for knowing the average concen-
tration over a time interval, AUC/t. Also, AUC is refer-
enced when talking about elimination. The amount elim-
inated by the body (mass) = clearance (volume/time) *
AUC (mass*time/volume).
2 AUC and bioavailability
In pharmacokinetics, bioavailability generally refers to
the fraction of drug absorbed systemically, and is thus
available to produce a biological effect. This is often
measured by quantifying the “AUC.” In order to deter-
mine the respective AUCs, the serum concentration vs.
time plots are typically gathered using C-14 labeled drugs
and AMS (accelerated mass spectroscopy) [1]
Bioavailability can be measured in terms of “absolute
bioavailablity” or “relative bioavailablity”
2.1 Absolute bioavailability
Absolute bioavailablity refers to the bioavailability of drug
when administered via a non-intravenous dosage form
(i.e. oral tablet, suppository, subcutaneous, etc.) com-
pared with the bioavailability of the same drug adminis-
tered intravenously. This is done by comparing the AUC
of the non-intravenous dosage form with the AUC for
the drug administered intravenously. This fraction is nor-
malized by multiplying by each dosage form’s respective
dose. [2]
Fₐ =(AUC ₒ -ᵢ ᵣₐᵥₑ ₒᵤ /AUCᵢ ᵣₐᵥₑ ₒᵤ ) * (Dᵢ ᵣₐᵥₑ ₒᵤ /D ₒ -
ᵢ ᵣₐᵥₑ ₒᵤ )
2.2 Relative bioavailability
Relative bioavailability compares the bioavailability be-
tween two different dosage forms. Again, the relative
AUCs are used to make this comparison and relative
doses are used to normalize the calculation.
Fᵣₑ =(AUC ₒ ₐ ₑA/AUC ₒ ₐ ₑB)* (DoseB/DoseA)
3 References
[1] Lappin, Graham; Rowland, Malcolm; Garner, R Colin
(2006). “The use of isotopes in the determination of ab-
solute bioavailability of drugs in humans”. Expert Opin-
ion on Drug Metabolism & Toxicology 2 (3): 419–27.
[2] Srinivasan, V. Srini (2001). “Bioavailability of Nutri-
ents: A Practical Approach to In Vitro Demonstration
of the Availability of Nutrients in Multivitamin-Mineral
Combination Products”. The Journal of Nutrition 131 (4
Suppl): 1349S–1350S.
4 See also
• Integral
1](https://image.slidesharecdn.com/areaunderthecurvepharmacokinetics-200202134701/85/Area-Under-the-Curve-Pharmacokinetics-1-320.jpg)
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Area Under the Curve (Pharmacokinetics)
- 1. Area under the curve (pharmacokinetics) In the field of pharmacokinetics, the area under the curve (AUC) is the area under the curve (mathematically known as definite integral) in a plot of concentration of drug in blood plasma against time. Typically, the area is computed starting at the time the drug is administered and ending when the concentration in plasma is negligi- ble. In practice, the drug concentration is measured at certain discrete points in time and the trapezoidal rule is used to estimate AUC. 1 Interpretation and usefulness of AUC values The AUC (from zero to infinity) represents the total drug exposure over time. Assuming linear pharmacodynamics with elimination rate constant K, one can show that AUC is proportional to the total amount of drug absorbed by the body. The proportionality constant is 1/K. This is useful when trying to determine whether two for- mulations of the same dose (for example a capsule and a tablet) release the same dose of drug to the body. An- other use is in the therapeutic monitoring of toxic drugs. For example, gentamicin is an antibiotic which displays nephro- and ototoxicities; measurement of gentamicin concentrations in a patient’s plasma and calculation of the AUC is used to guide the dosage of this drug. AUC becomes useful for knowing the average concen- tration over a time interval, AUC/t. Also, AUC is refer- enced when talking about elimination. The amount elim- inated by the body (mass) = clearance (volume/time) * AUC (mass*time/volume). 2 AUC and bioavailability In pharmacokinetics, bioavailability generally refers to the fraction of drug absorbed systemically, and is thus available to produce a biological effect. This is often measured by quantifying the “AUC.” In order to deter- mine the respective AUCs, the serum concentration vs. time plots are typically gathered using C-14 labeled drugs and AMS (accelerated mass spectroscopy) [1] Bioavailability can be measured in terms of “absolute bioavailablity” or “relative bioavailablity” 2.1 Absolute bioavailability Absolute bioavailablity refers to the bioavailability of drug when administered via a non-intravenous dosage form (i.e. oral tablet, suppository, subcutaneous, etc.) com- pared with the bioavailability of the same drug adminis- tered intravenously. This is done by comparing the AUC of the non-intravenous dosage form with the AUC for the drug administered intravenously. This fraction is nor- malized by multiplying by each dosage form’s respective dose. [2] Fₐ =(AUC ₒ -ᵢ ᵣₐᵥₑ ₒᵤ /AUCᵢ ᵣₐᵥₑ ₒᵤ ) * (Dᵢ ᵣₐᵥₑ ₒᵤ /D ₒ - ᵢ ᵣₐᵥₑ ₒᵤ ) 2.2 Relative bioavailability Relative bioavailability compares the bioavailability be- tween two different dosage forms. Again, the relative AUCs are used to make this comparison and relative doses are used to normalize the calculation. Fᵣₑ =(AUC ₒ ₐ ₑA/AUC ₒ ₐ ₑB)* (DoseB/DoseA) 3 References [1] Lappin, Graham; Rowland, Malcolm; Garner, R Colin (2006). “The use of isotopes in the determination of ab- solute bioavailability of drugs in humans”. Expert Opin- ion on Drug Metabolism & Toxicology 2 (3): 419–27. [2] Srinivasan, V. Srini (2001). “Bioavailability of Nutri- ents: A Practical Approach to In Vitro Demonstration of the Availability of Nutrients in Multivitamin-Mineral Combination Products”. The Journal of Nutrition 131 (4 Suppl): 1349S–1350S. 4 See also • Integral 1
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