Methods To Detect Absorption Rate Constant. ➢ Method of Residuals. ➢ Wagner- Nelson Method. ➢ Loo – Riegelman Method. ➢ Deconvolution Method. The Loo-Riegelman absorption method provides the correct A∞/V1 value and the correct rate constant ka (if absorption is first order), whether metabolism. LOO RIEGELMAN METHOD Wagner-Nelson method can be used only to determine Ka of a drug with one compartment charecteristic. Wagner.

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Application of the Loo-Riegelman absorption method.

Five Methods of Determining Proximity Damages. Semi-log plot of Cp versus Time after Oral Administration. Plasma drug level Back extrapolated terminal portion of curve Residual curve Time hours Lag time t0 Figure 4.

Some alternate methods for calculating the intrinsic absorption rate of drugs. For a drug that follows one compartment kinetics and administered extravascularly, the concentration of drug in plasma is expressed by a biexponential equation 7. Wagner-Nelson Method for estimation of Ka: It require both the data after oral and IV administration in same subject.

It is denoted by symbol t o and represents the beginning of absorption process. The Loo- Riegelman method requires plasma methov concentration — time data both after oral and i. Howeverwhen conc vs time curve after oral administration shows multi compartmental characteristics and on IV administration shows one compartmental model, analysis by this method gives incorrect result.


Methods Of Determining Absorption Rate Constant

This method can be applied to drug that can distributed by any number of compartments. Dividing the equation 3.

After oral administration of a single dose of a drug, at any given time, the amount of drug absorbed into the systemic circulation X Ais the sum of amount of drug in the body X and the amount of drug eliminated from the body X E. Applied Biopharmaceutics and pharmacokinetics by Leon shargel. Substitution of values of X and X E in equation 1 yields: Thus, the method of residuals enables resolution of the biexponential plasma level time curve into its two exponential components.


Determination of lag time by graphically. Reference Biopharmaceutics and Pharmacokinetics A treatise by D. With the increase in absorption rate constant, C max also increases.

It requires the plasma concentration time data after i. It is assumed that the absorption and elimination processes both follow the first order, if not the residual line and, perhaps, the elimination line will not be straight.

Example To Calculate Ct values. Documents Flashcards Grammar checker. The Wagner-Nelson method of calculation does not require a model assumption concerning the absorption process. The presentation is successfully added In Your Favorites. Parameters K 12K 21K 10 can be obtained by plasma concentration- time data after oral administration.


Methods Of Determining Absorption Rate Constant

When there is lack of sufficiently sensitive analytic techniques to measure concentration of drugs in plasma, urinary excretion data is used. Tozer, Clinical Pharmacokinetics,concepts and Applications, third edition,Waverly.

Skip to search form Skip to main content. Linear distribution and elimination are assumed. WordPress Embed Customize Embed. This is called as flip-flop phenomenon since the slopes of the two lines have exchanged their meanings. It requires no assumptions regarding the no of compartments or kinetics of absorption.

Application of the Loo-Riegelman absorption method

Types of Rate Laws. Metzler Journal of pharmaceutical sciences Email Presentation to Friend.

Unit Rate as the Constant of Proportionality Lesson 7. Semi-log Plot of Cp versus Time after oral administration of single dose Substracting of true plasma concentration values i. It is assumed that the absorption and elimination processes both follow the first order, if not metnod residual line and, perhaps, the elimination line will not be straight.