2017-AccessPharmacy - Pharmacokinetics Of Drug Absorption

By Brian Winkel


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AccessPharmacy (McGraw Ill). Applied Biopharmaceutics & Pharmacokinetics. Chapter 7.  Pharmacokinetics of Oral.

See https://accesspharmacy.mhmedical.com/book.aspx?bookID=1592 .  Accessed 7 September 2017.

From the web page.

“The pharmacokinetics of drugs following intravenous drug administration are more simple to model compared to extravascular delivery (see , , , , , and ). Extravascular delivery routes, particularly oral dosing, are important and popular means of drug administration. Unlike intravenous administration, in which the drug is injected directly into the plasma, pharmacokinetic models after extravascular drug administration must consider systemic drug absorption from the site of administration, e.g., the lung, the gut, etc., into the plasma. Extravascular drug delivery is further complicated by variables at the absorption site, including possible drug degradation and significant inter- and intrapatient differences in the rate and extent of absorption. Absorption and metabolic variables are characterized using pharmacokinetic methods. The variability in systemic drug absorption can be minimized to some extent by proper biopharmaceutical design of the dosage form to provide predictable and reliable drug therapy (, , and ). The major advantage of intravenous administration is that the rate and extent of systemic drug input is carefully controlled.

“The systemic drug absorption from the gastrointestinal (GI) tract or from any other extravascular site is dependent on (1) the physicochemical properties of the drug, (2) the dosage form used, and (3) the anatomy and physiology of the absorption site. Although this chapter will focus primarily on oral dosing, the concepts discussed here may be easily extrapolated to other extravascular routes. For oral dosing, such factors as surface area of the GI tract, stomach-emptying rate, GI mobility, and blood flow to the absorption site all affect the rate and the extent of drug absorption. In pharmacokinetics, the overall rate of drug absorption may be described as either a first-order or zero-order input process. Most pharmacokinetic models assume first-order absorption unless an assumption of zero-order absorption improves the model significantly or has been verified experimentally.”

Step by step formation of drug absorption models is shown with many good graphics of system and plots. Solutions are offered but no solution methods are show. The goal is to determine the rate constant and some of the strategies are the same ones employed by chemists of old, namely reading slopes of tangent lines. Hypothetical data, but no real data, is offered and modeled.

Keywords: pharmacokinetics, kinetics, differential equation, model, first order, system, Michaelis-Menten, enzyme, substrate, urinary data, rate constant, compartment, absorption rate

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Researchers should cite this work as follows:

  • Brian Winkel (2017), "2017-AccessPharmacy - Pharmacokinetics Of Drug Absorption," https://www.simiode.org/resources/3991.

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