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1. PHARMACOKINETICS
A HEMANTHBABU MPHARM,
HOW DRUG REACTS IN OUR BODY

2. • Mechanism of ABSORPTION
• Mechanism of DISTRIBUTION
• Mechanism of METABOLISM
• BIOTRANSFORMATION OF DRUGS
• Mechanism of ELIMINATION
CONTENTS :-

3. ABSORPTION
• The biological membrane of the body and the qualities of the medicine
govern the mechanism by which it enters the systemic circulation. It
happens when administered through various methods.
• BIOAVAILABILITY: A portion of the administered medication must enter
the bloodstream for it to have an unaltered e
ff
ect.
• Di
ff
erent types of modes and their tranportation of drugs are:
• PASSIVE TRANSPORT: In this mode there is no requirement of energy.
• PASSIVE DIFFUSION: In this system, the transportation occurs by di
ff
usion
with help of concentration gradient.
DEFINITION:-

4. • FACILIATED DIFFUSION: it is also on type di
ff
usion which helps to
transport drug through a particular proteins are termed as Carrier
protiens.
• ACTIVE TRANSPORT: In this transportation method the usage of ATP
occurs. And it has 2 types are -
• Primary active transport: It is direct transportation of molecules by
utilisation of ATP. Example is ABC transporters.
• Secondary active transport: It requires electrochemical gradient to drives
the uphill and downhill movement by using ATP.

5. • Lipid - water partition co-e
ff
icient of drug
• pKa value of drug
• Degree of plasma protein binding
The medicinal product is absorbed and moves through a number of
physiological
f
luids, including plasma, intestinal
f
luid, trans cellular
f
luid,
and intercellular
f
luid.
DISTRUBUTION
Vd =
Total amount of drug absorbed
_______________________________________
Plasma concerntration
Factors a
ff
ecting volume of distribution :-

6. • A
ff
inity of di
ff
erent tissues
• Fat - lean body mass ratio
• Diseases conditions
Modes of distrubution
BLOOD BRAIN BARRIER :-
This has no shortage of paracellular gaps despite the tightly packed,
connected cells.Lipid-soluble medications are permitted. Catecholamines,
which are highly selective for entrance into particularised pharmaceuticals,
are also among its specialised components.

7. PLACENTA BARRIER :-
They also have allowance of liphophillic but not hydrophilic drugs . It
limits foetal exposure of maternally administered drugs . And also it is
site for metabolism for drugs . However, the high concentration drugs
taken for longer period may allow placenta
PLASMA PROTIEN BINDING:-
The majority of medications have a strong propensity for binding to
plasma, which is a reversible mechanism.
Example:Acidic drugs — Albumin
Basic drugs — alpha 1 glycol protein

8. TISSUE STORAGE:-
Some medications may induce local toxicity, such as the discoloration of
the bone and teeth caused by tetracycline, or they may collect in certain
organs and bind to particular tissues by active transport.
METABOLISM - BIOTRANSFORMATION
The term "biotransformation" describes the metabolic changes occurring
in a given molecule, medication, or xenobiotic. Contrarily, metabolism
describes all of the biochemical processes occurring within a living
organism. EXAMPLE: xenobiotics elimination depends upon water
soluble catalysation

9. REACTION HOW IT OCCURS
OXIDATION
It is addition of oxygen radicals to compound. It occurs by
monooxygenase enzymes are cytochromeP450 & NADPH etc.,
REDUCTION
It is additional hydrogen radical and it opposes reaction of
cytochrome P450
HYDROLYSIS
This is cleavage of drug molecules by addition of water .it
occurs at liver , intestine , plasma etc., for carboxyesterases,
peptides , epoxide hydrolyses
CYCLIZATION Formation of ring formation example: progunail
DECYCLIZATION Breakdown of ring molecules example: Barbiturates
They are broadly classi
f
ied as 2 types are
PHASE 1 :-

10. REACTION HOW IT OCCURS
Glycoronide conjugation
We observe these mechanism in hydroxyl and
carboxylic acid combined drugs
Sulfate conjugation It is performed by sulfotransferase EX: methlydopa
Aminoacid
The metabolism can done by glycine taurine or
glutamine
Acetylation It is for amino acid residues and hydrazine residues
Methylation We observe in phenols and amines containing drugs
PHASE 2 REACTIONS:-
In this there is so many reactions are named, in that we discuss some
of the reactions

11. ELIMINATION
The body's procedures for drug removal are quite intricate. Although
each organ system has a distinct purpose, the tissues that make up each
organ are not all anatomically the same, and each organ may have a
di
ff
erent elimination mechanism. An overall
f
irst-order elimination rate
method was used to model drug eradication. This chapter describes drug
elimination as being cleared from a
f
ictitious well-stirred compartment
with a uniform drug distribution. The word "clearance" refers to the
process of medication removal from the body or from a speci
f
ic organ
without mentioning the speci
f
ic processes at play. The volume of
f
luid
cleared of drugs from the body per unit of time might be referred to as
clearance. Clearance is measured in litres per hour (L/h) or millilitres per
minute (mL/min).

12. EXAMPLES:-
KIDNEY —> Majority of drugs
LUNGS —> Removal of alcohols and anaesthetics
INTESTINE —> Ampillicin and erthyomycin
SALIVA —> Lithium, potassium, iodide
MILK —> Lipid soluble drugs
DRUGS
ORGANS

13. For elimination they obey some properties
First order elimination kinetics : “Elimination of a constant fraction
per time unit of the drug quantity present in the organism. The
elimination is proportional to the drug concentration.”
Zero order elimination: a constant amount of drug is eliminated per
unit time. For example 10mg of a drug maybe eliminated per hour,
this rate of elimination is constant and is independent of the total drug
concentration in the plasma. Zero order kinetics are rare Elimination
mechanisms are saturable.