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 – Semantic Scholar

Tozer, Clinical Pharmacokinetics,concepts and Applications, third edition,Waverly. By clicking accept or continuing to use the site, you agree to the terms outlined in our Ruegelman PolicyTerms of Serviceand Dataset License. The Loo- Riegelman method requires plasma drug concentration — time data both after oral and i. Equation 1 can be written as.

For a drug that follows one-compartmentkinetics and administered extra vascularlly, the time course of drug concentration in plasma is expressed by a bi exponential equation 1.

Parameters K 12K 21K 10 can be obtained by plasma concentration- time data after oral administration. The biexponential curve has been resolved into its two components- absorption and elimination. Plot log concentration of drug versus time. Applied Biopharmaceutics and pharmacokinetics by Leon shargel. It is assumed that ka is at least five times larger than k el, if not neither constant can be determined accurately. However, if such an intersection occurs at a time greater than zero, it indicate time lag.

You do not have the permission to view this presentation. Find AUCt0 by plotting Cp versus time. Semi-log plot of Cp versus Time after Oral Administration.


K E is obtained from plot of log C versus t and are obtained from plots of C versus t. This method can be applied to drug that can distributed by any number of compartments. Lag time should not be confused with onset time. Atomic Absorption Spectroscopy.

The time delay prior to the commencement of the first order drug absorption is known as Lag time t 0. Topics Discussed in This Paper.

Application of the Loo-Riegelman absorption method.

In this method of calculation it eiegelman important to remember that the following assumptionsare made:. Ka can similarly be estimated from urinary excreation data In cases where there is metabolism in compartment 2, the disposition parameters estimated from intravenous data are only apparent and not the real values.

Textbook of Biopharmaceutics and Pharmacokinetics by Dr.

Absorption half life can then be computed from K a using the relation 0. 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 riegelmzn of amount of drug in the body X and the amount of drug eliminated from the body X E.

Assuming first-order elimination kinetics with renal elimination constant ke 5.

Application of the Loo-Riegelman absorption method.

Loading SlideShow in 5 Seconds. The method of residual is used for the drugs which follow one or multi compartmental characteristics but the absorption process should not be complex. Metzler Journal of pharmaceutical sciences Transport of drug across the capillary membrane and into the systemic circulation 4 The overall rate of riegeoman drug absorption from an orally administered solid Dosage form is combination of many individual process including.


Percent drug unabsorbed at any time is therefore: For a drug following intravenous administration and confer multy compartmental characteristics.

Automatically changes to Flash methkd non-Flash embed. This method requires collection of blood samples riegelmman a single oral dose at regular of time intervals till the entire amount of drug is eliminated from the body. 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.

Despite its complexity the method can be applied to drugs that distribute in any number of components. Wagner-Nelson Method for estimation of K a One mrthod the better alternatives to curve fitting method in the estimation of K a is Wagner-Nelson method.

In some instances, the K E obtained after IV bolus of the same drug is very large, much larger than K a obtained by the method of residuals e.

Go to Application Have a question? For a drug that follows one compartment kinetics and administered extravascularly, the concentration of drug in plasma is expressed by a biexponential equation 7 PowerPoint Presentation: The amount of drug eliminated at any time t can be calculated as follows: The method involves the determination of K a from percent unabsorbed time plots and does not require assumption of zero or first order absorption.

John Meethod WagnerCarl M.

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