This document provides an overview of pharmacokinetics, which is the quantitative study of how the body acts on drugs. It describes the four main components of pharmacokinetics - absorption, distribution, metabolism, and excretion. Absorption refers to how drugs enter the bloodstream, distribution is how drugs spread to tissues, metabolism is how drugs are chemically altered, and excretion is how drugs and their metabolites leave the body. Key factors that determine a drug's pharmacokinetic properties and how it behaves in the body are also discussed.

2. What Is pharmacokinetic?
introduction
 How the human body act on the drugs?
 Pharmacokinetics is the quantitative study of
drug movement in, through and out of the body.
Intensity of effect is related to concentration of
the drug at the site of action, which depends on
its pharmacokinetic properties.
 Pharmacokinetic properties of particular drug is
important to determine dose, the route of
administration ,onset of action, peak action time,
duration of action and frequency of dosing.

3.  Pharmacokinetics has four component:-
ABSORPTION 01
DISTRIBUTION02
METABOLISM 03
EXCRETION04

4. ABSORPTION
• Absorption is the transfer of a drug from
its site of administration to the blood
stream .
• Most of drugs are absorbed by the way of
passive transport.
• Intravenous administration has no
absorption.
• Fraction of administered dose and rate of
absorption are important.

6. bioavailability
• Bioavailability refers to the rate and extent of
absorption of a drug. It is a measure of the fraction
(F) of administered dose of a drug that reaches the
systemic circulation in the unchanged form.
• Bioavailability of drug injected i.v. is 100%, but is
frequently lower after oral ingestion, because:
- The drug may be incompletely absorbed
-The absorbed drug may undergo first pass
metabolism in intestinal wall and/or liver or be
excreted in bile.

8. DISTRIBUTION
• It is the passage of drug from the circulation
to the tissue and site of its action.
•The extent of distribution of drug depends on
its lipid solubility, ionization at physiological
pH (dependent on pKa), extent of binding to
plasma and tissue proteins and differences in
regional blood flow, disease like CHF,
uremia, cirrhosis
•Movement of drug - until equilibration
between unbound drug in plasma and tissue
fluids

9.  Definition: Apparent Volume of distribution is
defined as the volume that would accommodate all
the drugs in the body, if the concentration was the
same as in plasma.
 Expressed as: in Liters
V = Dose administered IV/ Plasma concentration
Total drug in body=1000mg
Plasma drug concentration= 50mg/ml
V=1000/50=20L
Volume of Distribution (V)

10. Factors influencing Vd
• Lipid solubility (lipid : water partition
coefficient)
• pKa of the drug
• Affinity for different tissues
• Blood flow – Brain Vs Fat
• Disease states
• Plasma protein Binding

12. Brain and CSF Penetration
 Blood brain barrier (BBB): includes the capillary
endothelial cells (which have tight junctions and lack
large intracellular pores) and an investment of glial
tissue, over the capillaries. A similar barrier is
located in the choroid plexus.
 BBB is lipoidal and limits the entry of non-lipid
soluble drugs (amikacin, gentamicin, neostigmine
etc.). (Only lipid soluble unionized drugs penetrate
and have action on the CNS)

13. METABOLISM
 Chemical alteration of the drug in the body .
 Aim: to convert non-polar lipid soluble compounds
to polar lipid insoluble compounds to avoid
reabsorption in renal tubules .
 Most hydrophilic drugs are less biotransformed and
excreted unchanged – streptomycin, neostigmine
and pancuronium etc.
 Biotransformation is required for protection of body
from toxic metabolites

14. Results of Biotransformation
 Active drug and its metabolite to inactive metabolites
– most drugs (ibuprofen, paracetamol,
chlormphenicol etc.)
 Active drug to active product (phenacetin –
acetminophen or paracetamol, morphine to
Morphine-6-glucoronide, digitoxin to digoxin etc.)
 Inactive drug to active/enhanced activity (prodrug) –
levodopa - carbidopa, prednisone – prednisolone
and enlpril – enlprilat) .
 No toxic or less toxic drug to toxic metabolites
(Isonizide to Acetyl isoniazide)

15. Phase-
1
phase
-2
Phases of
metabolism
01 Phase1 or
non
systemic
metabolite
may be
active or
inactive
.
02 Phase2 or
systemic
metabolites are
inactive

16. Phase -1
 It includes oxidative ,reductive and hydrolytic
biotransformation.
 The main purpose of it, to introduce a functional
group into xenobiotic molecule to produce more
water soluble compound.
 They do not sufficientlyproduce inactive
metabolites but mainely tend to provide
functional groups that can go to phase-2
reactions.

17. A. Reductive
reaction
01
B. Hydrolytic
reaction 02
C. Oxidative
reaction
03
Types of
phase-1
reaction

18. PAHASE-2
 These are true detoxification reaction and are also
known as conjugational reactions.
 It involves covalent attachment of small polar
endogenous molecule such as sulfate, glycine etc to
either unchanged drug or phase-1 product having
suitable functional groups resulting in formation of
highly water soluble conjugate tha are excreted by
kidney.
 Enzymes involved in these reaction is tansferase
which is mainly found in liver.

19. Glucuronic acid
conjugation
Sulfate
conjugation
Conjugation with
glycine,glutamine and
other amino acid
ACETYLATION
METHYLATION
Glutathione or
mercaptopuric
acid conjugation

20. Factors affecting
Biotransformation
 Concurrent use of drugs: Induction and inhibition.
 Genetic polymorphism.
 Pollutant exposure from environment or industry.
 Pathological status.
 Age

21. EXCRETION
 Excretion is a transport procedure which the prototype
drug (or parent drug) or other metabolic products are
excreted through excretion organ or secretion organ.
 Hydrophilic compounds can be easily excreted.
 Routes of drug excretion -:
-Kidney
-Biliary excretion
- Sweat and saliva
-Milk
-Pulmonary

22. Hepatic Excretion
 Drugs can be excreted in bile, especially when the are
conjugated with – glucuronic Acid
 Drug is absorbed → glucuronidated or sulfatated in
the liver and secreted through the bile → glucuronic
acid/sulfate is cleaved off by bacteria in GI tract →
drug is reabsorbed (steroid hormones, rifampicin,
amoxycillin, contraceptives)
 Anthraquinone, heavy metals – directly excreted in
colon

23. 1.Glomerular filtration
AOPTION
2.Tubular
reabsorption
BOPTION
3.Tubular
secretion
COPTION
RENAL
EXCRETION

24. THANK YOU
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