Pharmacokinetics

1. PHARMACOKINETIC
Sameer Ganjave
Msc Part 2 : Roll No 08
Organic paper 4

2. PHARMACOKINETIC
Introduction: Pharmacokinetics
Absorption
Distribution
Metabolism
Elimination

3. INTRODUCTION: PHARMACOKINETICS
Pharmacokinetics (Greek: Kinesis—movement) — What the body
does to the drug. Pharmacokinetics is the quantitative study of drug
movement in, through and out of the body. This refers to movement
of the drugs absorption, distribution, biotransformation (metabolism)
and elimination of the drug.
After entry of the drug into the systemic circulation either by
intravascular injection or by absorption from any extravascular site,
drug is followed different processes by which changes in its plasma
concentration called disposition processes.

5. ABSORPTION
Absorption is the movement of the drug from its site of
administration to the blood stream. Rate and efficiency of
absorption depend on the route of administration.
Routes of drug administration
The route of administration is determined by the
properties of the drug and by the therapeutic objectives.
There are two major routes of drug administration,
enteral and parenteral.

6. Enteral 1.
Oral: Giving a drug by mouth is the
most common route of administration,
but it is also the most variable, and
requires the most complicated pathway
to the tissues
Sublingual: Placement under the
tongue allows the drug to diffuse into
the capillary network and therefore to
enter the systemic circulation directly.
Rectal: Fifty percent of the drainage of
the rectal region bypasses the portal
circulation; thus the biotransformation
of drugs by the liver is minimized
Parenteral :Parenteral administration is
used for treatment of unconscious
patients and under circumstances that
require a rapid onset of action.
Parenteral administration provides the
most control over the actual dose of
drug delivered body

7. Commonly used routes of drug
administration.

8. FACTOR AFFECTING DRUG ABSORPTION-
Factor affecting drug absorption-
Blood flow to the absorption site:
Aqueous solubility:
Route of administration

9. DISTRIBUTION
Distribution is the delivery of drug from the systemic
circulation to tissues. Once a drug has gained access to
the blood stream, it gets distributed to other tissues that
initially had no drug, concentration gradient being in the
direction of plasma to tissues. Distribution is defined as
the reversible transfer of drugs between body fluid
compartments. Distribution of a drug depends on its-
Lipid solubility

10. AFFECTED BY THE FOLLOWING
FACTORS:
1. Blood Flow
2. Capillary permeability
3. capillary structure
4. blood brain barrier
5. Binding of Drugs to proteins

11. BINDING OF DRUGS TO PLASMA
PROTEINS
Bound drugs are pharmacologically inactive, only the free, unbound drug
can act on target sites in the tissues, elicit a biologic response & be
available to the processes of Elimination
Note : ALBUMIN has the strongest affinity for ANIONIC DRUGS &
HYDROPHOBIC DRUGS.

12. DRUG METABOLISM
Drugs are often eliminated by biotransformation and or excretion into the URINE OR BILE
LIVER – THE MAJOR SITE FOR DRUG METABOLISM.
Reactions of Drug Metabolism
The kidney cannot efficiently eliminate lipophilic drugs , therefore lipid soluble agents
must 1st be metabolized in the liver using 2 general sets of reactions Eg.Phase 1 and
Phase 2
Phase 1/ Non synthetic / functionalization reaction:
Functional group is generated or exposed
Metabolite may be active or inactive
Phase 2/ synthetic / conjugation reaction:
Metabolite is mostly inactive ; except few drugs e.g. glucuronide conjugate of morphine
and sulfate conjugate and minoxidil are active.

13. DRUG ELIMINATION
Removal of a drug from the body may occur via a number of routes, the most important
being the kidney or urine.
Drugs that have been made water soluble in the liver are often readily excreted in the kidneys.
Kidney dysfunction can lead to toxic levels of the drug in the body because the drug cannot be
excreted
Other routes:
Intestine, lung, milk

14. REFERENCES……
Principle of medicinal chemistry vol.1, Dr S.S. Kadam, Dr K.R. Mahadik, Dr. S.S. Jadhav.
A Book of Medicinal chemistry Dr. Wilson and Gisvold’s.