This course was prepared by Dr.Osman Abdulahi Farah Cismaan shiine Lecturer of Gollis University Faculty of Agriculture and Veterinary Medicine 2014 The main content of this course including introduction of Veterinary Pharmacology, division of pharmacology and list of terms of terminology about veterinay pharmacology

1. Gollis University
Faculty of Agriculture and Veterinary
Medicine
Introduction to Veterinary
Pharmacology
LECTURER: Dr.Osman Abdulahi Farah
Date: 24 th nov 2014

2. Introduction
Pharmacology can be defined as the study of
substances that interact with living systems
through chemical process, by binding to
regulatory molecules activity or inhibiting normal
body process.
 applications may be considered the proper role of
Veterinary pharmacology, which is often
defined as the science of substances used to
prevent, diagnose, and treat disease for live
animals.
 Toxicology is that branch of pharmacology
which deals with the undesirable effects of
chemicals on living systems, from individual cells
to complex ecosystems.

3. introduction
Veterinary Pharmacology is divided into two main
subdivisions, pharmacokinetics and
1. pharmacodynamics .
2.Pharmacodynamics is the study of the
actions of drug on target organs. nd way of
thinking about it is that
pharmacodynamics (PD)is what the drug does to
the body,

4. Vet Pharmacokinetics(PK)
Vet Pharmacokinetics is What the body does to drug
 Modern pharmacology is focused on the
biochemical and molecular mechanisms by which
drugs produce their physiologic effects and with
the dose-response relationship , defined as
the relationship between the concentration of a
drug in a tissue and the magnitude of the tissue’s
response to that drug.

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Most Vet drugs produce their effects
by binding to protein receptors in
target tissues, a process that
activates a flow of events known
as signal transduction .

6. Vet Drug Nomenclature
Chemical name  represents the exact description of
the drug’s chemical composition
Example 1: the chemical name 2-methyl-5-
nitroimidazole-l-ethanol is metronidazole. The word
methylnitro is condensed to metro and ni-dazole is
due to its imidazole ring
Example 2: Metoclopramide is the condensed form
of the word methoxychloroprocainamide: where Me
is retained and th is written as t; chloro is written
as clo: and procainamide is written as pramide

7. Generic name
Generic name
Name that was established when drug
was first manufactured
Written in lowercase letters
Official name of a drug
Each drug has only one generic name
Original manufacturer is only company
that can use generic name for the first
17 years

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 Brand or trade name  is developed by the company
requesting approval for the drug and identifies it as the
exclusive property of that company.
 Is Name under which the drug is sold by a specific
manufacturer
 Spelling always begins with a capital letter
 Name is owned by the drug company and no other
company may use that name
 Example 1: Metrogyl® is the trade name for metronidazole.
 Example 2: Reglan® is the trade name for Metoclopramide.
 Example 3: Amoxil® is the trade name for amoxycillin.
 Example 4: Celebrex® is the trade name for Celecoxib

9. Pharmacokinetics is the
description of the time course of a
drug in the body, encompassing
Absorption, Distribution, Metabolism,
and excretion/Elimination. ADME
In simplest terms, it can be described
as what the body does to the drug.

11. The relationship between these
subdivisions and tissues over time,
including drug absorption,
distribution,
biotransformation (metabolism) ,
and excretion .

12. Absorption
It is the passage of drug from the site of
administration into the circulation.
 Bioavailability: is the extend to which a drug reaches its site of
action or to biological fluid such as plasma from which the drug
has access to its site of action
Aqueous solubility. Drugs given in solid
form must dissolve in the aqueous
biophase before they are absorbed. For
poorly water soluble drugs (aspirin,
griseofulvin) the rate of dissolution
governs the rate of absorption. If a drug is
given as water solution, it is absorbed
faster than the same given in solid form or

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Concentration. Passive transport depends
on the concentration gradient. A drug
given as concentrated solution is absorbed
faster than dilute solution.
Area of absorbing surface. If the area is
larger, the absorption is faster
Route of administration affects drug
absorption, because each route has its
own custom

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Oral application. Unionized lipid soluble
drugs (e.g.ethanol) are readily absorbed
from GIT. Acid drugs (aspirin,
barbiturates, etc.) are predominantly
unionized in the acid gastric juice and are
absorbed from the stomach. Acid
drugs absorption from the stomach is
slower, because the mucosa is thick,
covered with mucus and the surface is
small

15. Factors affect drug absorption
1.dose , concentration of rate
administration
2. Dosage form
3. Physical and chemical properties
4. Route of administration

16. Distribution
Distribution: is the passage of a drug from
the circulation
to the tissue and the site of its action.
The extent of distribution of a drug
depends on its lipid solubility, ionization at
physiological pH (dependent on pK),
extent of binding to plasma and tissue
proteins, and differences in regional blood.

17. flow, disease like CHF, uremia,
cirrhosis. Movement of a drug
proceeds until an equilibration is
established between unbound drug in
plasma and tissue fluids

18. Body fluid compartments
The total body water as a percentage of
body mass varies from 50% to 70%, being
rather less in women than in man.
Body water is distributed into the
following main compartments

19. Metabolism(Biotransformation)
 Metabolism includes chemical alteration of the
drugs in the body. Most hydrophilic drugs
(amikacin, gentamycin, neostigmine, mannitol)
are not biotransformated and are excreted
unchanged. The mechanism to metabolize drugs
is developed to protect the body from toxins.
The primary site for drug metabolism is the liver,
other sites are the kidney, intestine, lungs, and
plasma
 Biotransformation reactions can be classified into
two phases: I (no synthetic) and II (synthetic,
conjugation).

20. Excretion
Excretion is the passage out of
systematically absorbed drugs.
Vet Drugs and their metabolites
are excreted in:
urine (through the kidney)
• bile and faeces
• exhaled air
• saliva and sweat,milk and skin

21. kidney
 The kidney is responsible for excreting all water soluble
substances.
Glomerular filtration. Glomerular capillaries have large pores.
All nonprotein bound drugs (lipid soluble or insoluble)
presented to the glomerulus are filtrated. Glomerular
filtration of drugs depends on their plasma protein binding
and renal blood flow. Glomerular filtration rate (g.f.r.)
declines progressively after the age of 50 and is low in
renal failure.
 Tubular reabsorption. Lipid soluble drugs filtrated at the
glomerulus back diffuse in the tubules because 99% of
glomerular filtrate is reabsorbed, but nonlipid soluble and
highly ionized drugs are unable to do so.

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 The effect of changes in urinary pH on drug excretion
 is greatest for a drug having pK values between 5 to 8,
 because only in this case pH dependent passive
 reabsorption is significant.
 Tubular secretion is the active transfer of organic acid and
bases by two separate nonspecific mechanisms, which
operate in the proximal tubules:
• Organic acid transport for penicillins,, methotrexate, drug
glucuronides, etc.
• Organic base transport for thiazides, quinine,
 procainamide, cimetidine, amiloride, etc.

23. Pharmacodynamics
Vet Pharmacodynamics is the
study of the biochemical and
physiological effects of drugs, in
certain period.
In brief, it can be described as what
the drug does to the body.
Drug receptors
Effects of drug
Responses to drugs
Toxicity and adverse effects of drugs

24. Drug Receptor Interactions
The Lock and Key Model of Signal-Receptor
Interaction
 Ligands such as hormones or neurotransmitters
(the"key") affect target cells by binding to specific
receptors (the "lock”), which are often located in
the cell membrane of animal body
 This binding "unlocks" the cell's response, so that
the hormone or neurotransmitter can exert its
effects
 Agonist
“A chemical messenger that binds to a receptor
and triggers the cell’s response; often refers to
a drug that mimics a normal messenger’s action”.
 For example, pilocarpine is a muscarinic receptor agonist
because it can bind to and activate muscarinic receptors

25. Drug Receptors
Receptor/Binding site
“A specific protein in either the plasma
membrane or interior of a target cell with which
a ligand/drug combines”
It must be selective in choosing ligands/drugs
to bind  To avoid constant activation of the
receptor by promiscuous binding of many
different ligands (drugs)
It must change its function upon binding in
such a way that the function of the biologic
system (cell, tissue, etc) is altered  This is
necessary for the ligand (drug) to cause a
pharmacologic effect

26.  Antagonist is "A molecule that competes for a receptor
with a chemical messenger normally present in the body.
The antagonist binds to the receptor but does not trigger
the cell’s response”
 For Example, atropine is a muscarinic receptor antagonist
because it can bind to muscarinic receptors but it does not
trigger the cell’s response. In this way, it prevents binding of
acetylcholine (ACh) and similar agonist drugs to the ACh recept
 Any drug will be toxic once they are overdosed.
 toxic dose; lethal dose

27. Drug Receptor Interactions
Agonist Receptor
Lock and key mechanism
Agonist-
Receptor
Interaction

28. Terminology of Pharmacology,
 Drug
“Any substance that brings about a change in biologic function
through its chemical actions”a
 Receptor
“A specific protein in either the plasma membrane or interior of a
target cell with which a chemical messenger/drug combines”
 Mechanism of Action
“The ways by which drugs can produce therapeutic
effects”
 Dose
“The amount of a drug to be administered at one time”
Duration
“The time a drug concentration is sufficient to elicit a
therapeutic response

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 Effects (therapeutic effect)
“The desired results of administration of a medication”
 Side Effects (adverse effects)
“Effects that are harmful and undesired, and that occur in addition
to the desired therapeutic effects”
 Indications
“The reasons for administering a medication or performing a
treatment”
Contra-indications
“Factor that prevents the use of a medication or treatment (
e.g., Allergies)”

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 Onset
“The time it takes for the drug to elicit a therapeutic
response
Bioavailability: is the extend to which a drug reaches its
site of action
 Pharmacotherapeutics is the medical science concerned
with
 the use of drugs in the treatment of disease.
 Pharmacognosy is the study of drugs isolated from
natural sources, including plants, microbes, animal tissues