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Module - IV Bolus

The document discusses the one-compartment model for intravenous drug administration. It describes the one-compartment model as assuming the drug distributes instantaneously and homogenously throughout the body after IV injection and is eliminated immediately from the compartment. The model is described by two parameters: apparent volume of distribution (Vd) and elimination rate constant (Ke). The concentration of drug in the body over time is shown to follow first-order kinetics and can be expressed by the exponential equation C=C0e-ket, where C0 is the initial concentration and t1/2 is calculated from Ke. A semilogarithmic plot of concentration vs. time results in a linear relationship that can be used to determine Ke and t

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115 views4 pages

Module - IV Bolus

The document discusses the one-compartment model for intravenous drug administration. It describes the one-compartment model as assuming the drug distributes instantaneously and homogenously throughout the body after IV injection and is eliminated immediately from the compartment. The model is described by two parameters: apparent volume of distribution (Vd) and elimination rate constant (Ke). The concentration of drug in the body over time is shown to follow first-order kinetics and can be expressed by the exponential equation C=C0e-ket, where C0 is the initial concentration and t1/2 is calculated from Ke. A semilogarithmic plot of concentration vs. time results in a linear relationship that can be used to determine Ke and t

Uploaded by

yashpandya01
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© Attribution Non-Commercial (BY-NC)
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M.

pharm -2008-2009, Trimester II Subject : Approaches to Analytical Method Development Title Name : RESOLUTION AND COLUMN EFFICIENCY : Roll no

Quality Assurance Code:PHA777

Page no.:

AIM: Study of one compartment model by intravenous bolus route of administration REQUIERMENTS THEORY: One-compartment open model assumes that the drug can enter or leave the
body (i.e., the model is "open"), and the body acts like a single, uniform compartment. The one-compartment model that describes the distribution and elimination after an IV bolus dose isThe simplest kinetic model that describes drug disposition in the body is to consider that the drug is injected all at once into a box, or compartment, and that the drug distributes instantaneously and homogenously throughout the compartment. Drug elimination also occurs from the compartment immediately after injection. In the body, when a drug is given in the form of an IV bolus, the entire dose of drug enters the bloodstream immediately, and the drug absorption process is considered to be instantaneous. In most cases, the drug distributes via the circulatory system to potentially all the tissues in the body. Uptake of drugs by various tissue organs will occur at varying rates, depending on the blood flow to the tissue, the lipophilicity of the drug, the molecular weight of the drug, and the binding affinity of the drug for the tissue mass. Most drugs are eliminated from the body either through the kidney and/or by being metabolized in the liver Because of rapid drug equilibration between the blood and tissue, drug elimination occurs as if the dose is all dissolved in a tank of uniform fluid (a single compartment) from which the drug is eliminated. The volume in which the drug is distributed is termed the apparent volume of distribution, V D. The apparent volume of distribution assumes that the drug is uniformly distributed in the body. The V D is determined from the preinjected amount of the dose in the syringe and the plasma drug concentration resulting immediately after the dose is injected. The apparent volume of distribution is a parameter of the one-compartment model and governs the plasma concentration of the drug after a given dose. A second pharmacokinetic parameter is the elimination rate constant, k, which governs the rate at which the drug concentration in the body declines over time. The one-compartment model that describes the distribution and elimination after an IV bolus dose is

Figure 1.
Date: Initial of student: Initial of faculty:

M.pharm -2008-2009, Trimester II Subject : Approaches to Analytical Method Development Title Name : RESOLUTION AND COLUMN EFFICIENCY : Roll no

Quality Assurance Code:PHA777

Page no.:

Rate of elimination is dX = rate in - rate out dt

where : Ke is the elimination rate constant X is the amount of drug in body at time = t C is the concentration of the drug in the body at time = t dx = 0 - KeX dt dX = -KeX dt Taking log on both sides, Log X = log X0 - Ke t
2.303

Taking Natural log, lnX = lnX0 - ket The exponential form of the equation is: X = X0 e-Ket

Where X0 is amount of drug at time t = 0 i.e initial amount of drug injected


Date: Initial of student: Initial of faculty:

M.pharm -2008-2009, Trimester II Subject : Approaches to Analytical Method Development Title Name : RESOLUTION AND COLUMN EFFICIENCY : Roll no

Quality Assurance Code:PHA777

Page no.:

Now,

X = CpVd (Vd = X/C)

Where Vd is the volume of distribution .. Log C = log C0 - Ke t


2.303

C = C0 e-Ket

Where C0 is plsama drug concentration immediately after i.v injection.

The semilograthmic plot of log C vs time will be linear with y intercept log C0 Ke (elimination rate constant) is directly obtained from slope of the line Half life (t1/2) is related to elimination rate constant by equation

t1/2 = 0.693 Ke

Date:

Initial of student:

Initial of faculty:

M.pharm -2008-2009, Trimester II Subject : Approaches to Analytical Method Development Title Name : RESOLUTION AND COLUMN EFFICIENCY : Roll no

Quality Assurance Code:PHA777

Page no.:

Date:

Initial of student:

Initial of faculty:

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