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Pharmacokinetics 819

setting all L i to zero and recalculating the tissue concen- The rate of absorption can be characterized from the cal-
trations and volumes. Thus this type of model is most culation of t residence for both i.v. administration and non-
valuable in the investigation of detailed mechanisms of i.v. administration. The mean absorption time (t absorption )
absorption, distribution, and elimination in the pharma- is calculated as the difference of the two mean residence
cokinetic simulation of a drug. times.
This method is chiefly descriptive and requires no un-
derstanding of the underlying mechanisms. It permits
C. Noncompartmental Model Approaches quantitative characterization of the kinetics of the drug
Noncompartmental pharmacokinetics has been developed in the central compartment. The advantage is that sophis-
as an alternative to data-intensive compartmental and ticated mathematics is unnecessary. This fact alone makes
physiologic models. While the latter techniques are use- noncompartmental methods particularly useful in the clin-
ful in pharmacokinetic predictions if sufficient data are ical use of drugs.
available, drugs with complex distribution and elimina-
tion may be difficult to properly model without additional SEE ALSO THE FOLLOWING ARTICLES
experimental data. The noncompartmental techniques do
not rely on specific distribution characteristics of a drug
ABSORPTION • BIOENERGETICS • ION TRANSPORT
and therefore become useful when data are limited.
ACROSSBIOLOGICALMEMBRANES•PHARMACEUTICALS,
The basis for noncompartmental methods for calcula-
CONTROLLED RELEASE OF
tion of the parameters of each step of absorption, dis-
tribution, and elimination is the theory of statistical mo-
ments. The information required is the drug concentration BIBLIOGRAPHY
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1
M AUC Chernow, B. (1995). “Critical Care Pharmacology,” Williams and
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1
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