This document discusses pharmacokinetic models, which are mathematical models used to predict how drugs move through the body over time. It describes several types of pharmacokinetic models including compartment models that divide the body into hypothetical compartments and non-compartment models. Compartment models include one, two, and multi-compartment models. Pharmacokinetic models can also be classified based on elimination rate constants, compartment arrangement, and physiology. The document provides examples and diagrams of different pharmacokinetic models and discusses their applications in drug development and clinical practice.

1. An assignment on
Pharmacokinetic Models
Submitted to:-
Mohammed Kamal Hossain
Assistant professor
University of science and technology,
Chittagong
Submitted by:-
Roll – 14301
Reg – 1078
Course Name: Biopharmaceutics-I
Course No:-PHR-305
Department of Pharmacy
University of science and technology, Chittagong

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Pharmacokinetic: Pharmacokinetics is a branch of pharmacology that determines the
fate of substances such as pharmaceutical drugs, pesticides, food additives, cosmetics
etc. from the moment that it is administered to a living organism up to the point at which
it is completely eliminated from the body.
Pharmacokinetics refers to the studies of rates of drug absorption, distribution,
metabolism and excretion (ADME). It determines change of ADME processes with
time.
 Absorption is defined as the process by which a drug proceeds from the site of
administration to the site of measurement (usually blood, plasma or serum)
 Distribution is the process of reversible transfer of drug to and from the site of
measurement (usually blood or plasma)
 Metabolism is the process of a conversion of one chemical species to another
chemical species
 Excretion is the irreversible loss of a drug in a chemically unchanged or
unaltered form
Fig:-Pharmacokinetic
Introduction

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Pharmacokinetic Models: It is a hypothetical consideration by which we predict
the drug dispositions in our body.
Pharmacokinetic model is a mathematical modeling technique for predicting the
absorption, distribution, metabolism and excretion of pharmaceutical drug.
Pharmacokinetic models are mathematical tools that allow simulating drug
concentration level in the blood prior to real administration. These models have
countless applications in new drug development and clinical activities.
We can classify pharmacokinetic model on the basis of –
1. Compartment
2. Elimination rate constant
3. Arrangement
4. Physiology
Pharmacokinetic model on the basis of Compartment: it is of two types
1) Compartment model
2) Non-compartment model
1) Compartment model:
Compartmental analysis is commonly used to estimate the pharmacokinetic
characters of a drug.
The compartments are hypothetical in nature
The body is represented as a series of compartments arranged either in series
or parallel to each other, that communicate reversibly with each other.
Types of pharmacokinetic Model
Pharmacokinetic
Models
Compartment model

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Each compartment is not a real physiologic or anatomic region and
considered as a tissue or group of tissues that have similar drug distribution
characteristics (similar blood flow and affinity).
Every organ, tissue or body fluid that can get equilibrated with the drug is
considered as a separate compartment.
The rate of drug movement between compartments (i.e. entry and exit) is
described by first-order kinetics.
Rate constants are used to represented to entry and exit from the
compartment.
Compartment model are further classified as-
 One compartment model
 Two compartment model
 Multi compartment model
One compartment model: In a one compartment model entire body acts like a single
compartment. Drug distribute instantly and homogenously.
It is unidirectional, here rate of absorption = rate of elimination.
Fig:-One compartment Model
One Compartment model

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Two compartment model: The two compartment model divides the whole body in two
compartment-
I. Central compartment: Blood, extracellular fluid and highly perfused
tissue. The drug distributes rapidly and uniformly in the central
compartment.
II. Tissue or peripheral compartment: Tissue in which the drug equilibrates
more slowly.
The two compartment model is not unidirectional, here rate of absorption is not
equal rate of elimination.
Fig:-Two Compartment Model
Multi compartment model: In multi compartment model the body is divided into many
compartment. According to this model the drug is distributed according to their
perfusion characteristics.
It is not unidirectional and here the rate of absorption is not equal to the rate of
elimination.
Two Compartment model
Multi Compartment model

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Fig:Multi Compartment Model
2) Non compartment model: it does not require the assumption of specific
compartment model.
There are two model on the basis of elimination rate constant. These are-
o Open model
o Closed model
Open model: it describes that administered drug dose is excreted from the body by a
excretory mechanism.
It is of two type
One compartment open model: for plasma
Fig:- One compartment open model
central
compartment
Tissue
compartment
Deep Tissue
Compartment
Drug Central Compartment Excretion
Pharmacokinetic model on the basis of Elimination rate
constant constant
Open model

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Two compartment open model: for tissue
Fig:- Two compartment open model
Closed model: the drug full dose does not eliminated from the body completely, some of
drug accumulates in deep tissue compartment.e.g:-Multicompartment model.
Fig:-Closed Model
Drug
Central
compartment
Pweripheral/Tissue
compartment
Excretion
Plasma
compartment
•Excretion
Tissue
compartment
•Excretion
Deep Tissue
Compartment
• No
Excretion
Closed model

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There are two model on the basis of arrangement of compartment. These are-
 Catenary model
 Mammillary model
Catenary model: It consists of compartment, joined to one another like the compartment
of a train.
Fig:-Catenary model
Mammillary model: it is the most common model used in pharmacokinetic.
Here one or more peripheral compartments are connected to a central compartment
(parallel to central compartment) which consist of plasma and highly perfused tissues.
Plasma Heart Liver Kidney
Pharmacokinetic model on the basis of Arrangement
Catenary model
Mammillary model

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Fig:-Mammillary model
it is two types.
Perfusion rate limited model
Diffusion limited model
Perfusion limited model: Here drugs can across the cell membrane without barrier.it is
limited by blood flow. This is only applicable to the highly membrane potential,
molecular weight, poorly ionized and highly lipophilic drug.
Diffusion limited model: these are more applicable to highly polar ionized and charged
drugs in which case the cell plasma barrier for the drug that gradually permeates by
diffusion.
1. Characterizing the behavior of drugs in patients
2. Predicting the concentration of drug in various body fluid with any dosage
regimen
3. Predicting the multiple dose concentration curves from single dose experiments
4. Calculating the optimum dosage regimen for individual patients.
5. Evaluating the risk of toxicity with certain dosage regimen.
6. Correlating plasma drug concentration with physiological response
Plasma
Heart
Liver
Kidney
Intestine
Pharmacokinetic model on the basis of Physiology
Applications of pharmacokinetic models

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7. Evaluating the bioequivalence between different formulations of the same drug
8. Estimating the possibility of drug accumulation in the body.
Bibliography
1.YU, Leon Shargel,Susanna Wu-Pung.Andrew. 2012. Applied Biopharmaceutics &
Pharmacokinetics. 6th. s.l. : McGraw-Hill, 2012. pp. 43-84. ISBN-13:978-007-
160393-5.
2.https://www.slideshare.net/SURYAKANTVERMA2/pharmacokinetic-models-
194807718?from_action=save
3.Weiner D,GabrielssonJ (2000). "PK24–Non-linearkinetics–flow
II". Pharmacokinetic/pharmacodynamic data analysis: concepts and applications.
Apotekarsocieteten. pp. 527–36. ISBN 91-86274-92-9.
4. Ruiz-Garcia A, Bermejo M, Moss A, Casabo VG (February 2008).
"Pharmacokinetics in drug discovery". Journal of Pharmaceutical Sciences. 97 (2):
654–90. doi:10.1002/jps.21009. PMID 17630642