Introduction to pharmacology
Dr. Sema Güler
Pharmacology
what is
pharmacology
• It is the science that studies what drug
molecules do to a living organism and
what the organism does to drug
molecules.
• It acts as a bridge between biology and
therapy.
Pharmacology
Pharmacology is a branch of science that
study of
Effects of drugs
 Properties of drugs
Their use in treatment
Drug effects at the molecular level
History
• People have been interested in the science of pharmacology since the
Antiquity.
• They got rid of disease and pain by using the flowers, leaves and roots
of some plants in nature.
• They increased their working power by chewing coca leaves. People
who use opium to relieve their pain unconsciously laid the foundation
for pharmacology.
Ebers Papirüsü
• The first systematic information about
medicines was extracted from the Ebers
papyri written in Egypt.
• Inscriptions from the Sumerian and Egyptian
periods also contain information about opium
and other medicinal plants.
BRANCHES OF PHARMACOLOGY
• Pharmacokinetics: It is the science that examines the absorption,
distribution, metabolism and excretion of drugs in vivo.
• Pharmacodynamics: It is the science that studies the physiological
and biochemical effects and mechanisms of action of drugs in living
things.
• Pharmacotherapy: It is the science that studies the use of drugs in the
prophylaxis and treatment of diseases.
• Molecular pharmacology: It is the science that studies the
interactions between biological systems and drugs in living things at
the molecular level.
• Biochemical pharmacology: It is the science that studies the
interactions between drugs and enzymes.
Pharmacotherapy
• It is the science that deals with the use of drugs in the prophylaxis
and treatment of diseases and their clinical application.
• There are several types of treatment. These;
➢ Empirical treatment; It is observation trial without knowing the
cause of the disease and the effect of the drug.
➢ Symptomatic (palliative) treatment; It is treatment with drugs to
relieve symptoms without removing the cause of the disease.
• Prophylactic treatment; drug applications to prevent diseases.
• Substitution therapy (replacement); It is the application of drugs to
eliminate the deficiency of substances in the body.
• Radical treatment (rational); It is the complete elimination of the
cause of the disease with medication.
Clinical pharmacology:
• It is a science that examines the application and evaluation of results
which chemical substances examined in experimental animals for the
purpose of finding and developing new drugs in normal and sick
people.
• Clinical pharmacology has developed to better reveal the effects and
outcome of drugs in a normal or pathological person.
Toxicology:
It is a branch of science that
examines poisoning caused by drugs or other chemical substances,
 the structure of toxic substances, properties, mechanisms , action
and symptoms of poisoning and
 treatments of poisonous substances.
Pharmacokinetics
Pharmacokinetics is the aspect of
pharmacology dealing with how drugs reach
their site of action and are removed from
the body.
It examines what the organism does to the
drug molecule.
Absorption
Distribution
Metabolism
 Elimination
Pharmacodynamics
• Pharmacodynamics is the study of a drug's molecular, biochemical,
and physiologic effects or actions
• Pharmacodynamics describes the intensity of a drug effect in relation
to its concentration in a body fluid, usually at the site of drug action.
• It can be simplified to 'what the drug does to the body'
• BIOPHARMACY: It examines the factors affecting the absorption of
drugs taken into the organism.
• Pharmacopeia- Codex
• The official book containing the qualitative and quantitative analysis
methods of the active and auxiliary substances used in the production
of drugs, and the national and international rules and methods that
must be followed legally and scientifically.
DRUG
• "Every medicine is poison, there is no substance that is not poison; It is
the dose that separates the drug from the poison. "
Paracelsus
• WHO (World Health Organization) defines the drug as;
❑"It is a substance that can be used to modify or study physiological
systems or pathological states for the benefit of the field."
• A drug molecule exerts effect the organism by imitating a
neurotransmitter or hormone
Placebo
• It is a drug form that is similar to the active drug in terms of
properties such as color, shape and odor, but does not contain any
active substance and has no pharmacological effect.
it will be
good for
me
But these drugs are
addictive drugs
No, I've been using it for
28 years, never did
SOURCES OF DRUGS
Treatment classification according to the
intended use
• 1. Preventive (prophylactic) treatment: It is the administration of a
drug to a healthy person in order to prevent a possible disease or to
temporarily change a physiological event.
• 2.Complementary (replacement) therapy: It is the application of drugs
to complete the deficiency caused by a deficiency in the organism.
• 3. Radical Treatment: It is the application of drugs for the cause of the
disease.
• 4. Symptomatic treatment (palliative treatment): It is the application
of drugs only to reduce the pathological disorders without eliminating
the cause of the disease.
Basic concepts about drug
• Dose: the amount of medicine that you should take at one time
• Drug(Drog): raw or semi-raw material obtained by collecting, used in
pharmacy and partially in industry
• Daily dose:recommended amount of medication during the day
• Side effect: is usually regarded as an undesirable secondary effect
which occurs in addition to the desired therapeutic effect of a drug or
medication.
• İndication" for a drug refers to the use of that drug for treating a
particular disease. For example, diabetes is an indication for insulin
• Contraindication is a specific situation in which a drug not be used
because it may be harmful to the person.
The three broad name classifications of drugs
are as follows:
1. Common name (generic=international common nomenclature):
The general name is used to provide international scientific partnership
in the field of health and to make scientific publications easy to
understand.
Example: Acetylcysteine ​(mucolytic = liquefies, dilutes mucus)
2. Proprietary/brand/trade name: These are names given to the drug
by the manufacturing and marketing company. The innovator company
can then exclusively market and sell this “brand-name” product during
the patent protection period. Copyright laws prevent any other person
from using the brand name
example: Dikloron, Difenak, Voltaren, Miyadren v.b.
• All drugs are analgesic, anti-inflammatory,
• drugs used as antirheumatic
3. Chemical/molecular/scientific name: It depicts the chemical/
molecular structure of the drug and states the structure in terms
of atoms and molecules accompanied by a diagram of the chemical
structur
Drug Equivalents
• Pharmaceutical Equivalence: Two different preparations contain the same
molar amount of the same active substance or substances in
pharmaceutical forms (tablet-capsule, ampoule-vial) conforming to the
same or comparable standards.
• Therapeutic Equivalence: The state of a preparation containing the same
active substance as another preparation whose efficacy and safety has
already been established, and clinically demonstrating the same efficacy
and safety.
• Approved drug products are considered to be therapeutic equivalents if
they are pharmaceutical equivalents for which bioequivalence has been
demonstrated, and they can be expected to have the same clinical effect
and safety profile when administered to patients under the conditions
specified in the labeling.
*same bioavaibility
*same therapeutic effect
• Bioequivalence: Two pharmaceutically equivalent preparations are so
similar that, after administration at the same molar dose, their
bioavailability (in terms of rate and degree of absorption) and thus
their therapeutic effects are the same in terms of both efficacy and
safety.
• When two formulations of the same drug or two drug products are
claimed bioequivalent, it is assumed that they will provide the same
therapeutic effect or that they are therapeutically equivalent. In this
case, most people interpret that they can be used interchangeably.
Pharmacokinetics
• The study of the disposition of a drug
• The disposition of a drug includes the processes of ADME
Absorption
Distribution
Metabolism
Excretion
Elimination
1. Absorption
The rate at which drug molecules reach the bloodstream after entering
the organism largely depends on the route of administration
Oral
It crosses the epithelial tissue and enters the
 Skin (percutaneous)
extracellular fluid.
After dispersion, it passes through the
Rectal
capillary wall and
reaches the bloodstream
Lung
Injection
epithelial tissue
IV- directly into the bloodstream
absent
Gastrointestinal Absorption
• Most drugs undergo gastrointestinal absorption. Absorption occurs
mostly in the duodenum. This is extent to which drug is absorbed
from gut lumen into portal circulation
• Exception: IV drug administration
oral tablet takes about 5-6 hours
to pass through the
gastrointestinal tract.
About 0.5-1 hour of this time in
the stomach, the rest of the time
passes at intestines
The drug through the membranes of the
digestive tract;
Passive diffusion
Active transport
Facilitated diffusion
Pinocytosis
Receptor-mediated endocytosis
• It is absorbed by these mechanisms.
First-pass hepatic metabolism (presystemic
elimination):
• When a drug is absorbed from the GI tract,
it enters the portal circulation before
entering the systemic circulation
• If the drug is rapidly metabolized in the liver
or gut wall during this initial passage, the
amount of unchanged drug entering the
systemic circulation is decreased. This is
referred to as first-pass metabolism. (Except
for drugs administered sublingually and
rectum)
• [Note: First-pass metabolism by the
intestine or liver limits the efficacy of many
oral medications.
Enterohepatic cycle
Drugs that are eliminated via the bile after hepatic
first pass may be metabolized in the intestine and
pass through the intestinal walls before being
excreted in the faeces. They can be reabsorbed.
In this way, the re-entry of the drug molecule into
the circulation is called the enterohepatic cycle.
(digitoxin, steroid, morphine)
Bioavailability
• Bioavailability is the rate and extent to which an administered drug
reaches the systemic circulation. For example, if 100 mg of a drug is
administered orally and 70 mg is absorbed unchanged, the
bioavailability is 0.7% or 70%.
• Determining bioavailability is important for calculating drug dosages
for non intravenous routes of administration
In IV injection
100% absorption
100% bioavailability
DRUG DISTRIBUTION
Drug distribution is the process by
which a drug reversibly leaves the
bloodstream and enters the
extracellular fluid and tissues.
For drugs administered IV, absorption is
not a factor, and the initial phase
immediately following administration
represents the distribution phase,
during which the drug rapidly leaves
the circulation and enters the tissues
Physiological fluid compartments in which drugs are
distributed
• The distribution of a drug from the plasma to the interstitium
depends on
• Cardiac output and local blood flow,
• Capillary permeability,
• Tissue volume,
• Degree of binding of the drug to plasma and tissue proteins,
• Relative lipophilicity of the drug.
The movement of drug from the blood
to and from the tissues
Drug concentrations in serum after a
single injection of drug. Assume that
the drug distributes and is subsequently
eliminated.
• Binding to plasma proteins (bound complex cannot reach tissues and
exert its pharmacological effect)
• Distribution to tissues (drug must cross cell membrane)
• Distribution to the central nervous system
• Feto-placental distribution
ELIMINATION
Elimination: The irreversible removal of
the parent drugs from the body
Elimination from the kidneys
Elimination through digestion
Elimination through the lung
Elimination via milk (for lactating
women)
Elimination through sweat
With all secretions in the body
(tears, genital secretions..)
Elimination
Excretion
Drug Metabolism
(Biotransformation
The biotransformation of drugs
• Relative contribution of
cytochrome P450 (CYP) isoforms
to drug biotransformation
• Phase I reactions utilizing the P450
system:
• The phase I reactions most frequently
involved in drug metabolism are
catalyzed by the cytochrome P450
system.
• The P450 system is important for the
metabolism of many endogenous
compounds (such as steroids and
lipids) and for the biotransformation of
exogenous substances (drugs,
carcinogens, and environmental
pollutants).
• Cytochrome P450 (CYP) is a
superfamily of heme-containing
isozymes located in most cells, but
primarily in the liver and GI tract.
• Phase II: This phase consists of conjugation reactions.
• If the metabolite from phase I is sufficiently polar, it can be excreted
by the kidneys.
• However, many phase I metabolites are still too lipophilic to be
excreted.
• A subsequent conjugation reaction with an endogenous substrate,
such as glucuronic acid, sulfuric acid, acetic acid, or an amino acid,
results in polar, usually more water soluble compounds that are often
therapeutically inactive and more water-soluble metabolite which are
readily excreted in urine or bile.
Pharmacodynamics
EXAMINES THE EFFECTS OF
DRUGS ON THE ORGANISMS.
• Drug molecules enter the organism and create desired (therapeutic)
and undesirable effects (side effects and toxic effects).
Adverse effect:
• The most important feature desired in the drug is that it affects only
the diseased structures and has minimal or no effect on other parts of
the body.
• There is hardly any such drug.
• Although liver necrosis, nephritis and pancreatitis caused by
paracetamol overdose are called toxic effects, less harmful skin
rashes and hematological changes can be named as side effects.
FACTORS CHANGING THE EFFECT OF DRUGS
• Weight
• Age
• Kidney failure
• Liver failure
• Gender
• Route and time of administration
• Pregnancy
• Tolerance
• Addiction
• Nutrients
• Genetics
• Presence of other drugs in the body
women are more sensitive to
drugs that affect the central
nervous system and to alcohol
fatty foods delays absorb of
drugs
DRUG INTERACTIONS
1. Pharmacodynamic interactions
• Pharmacodynamic interactions occur between drugs that act on the
same receptor.
• One drug can increase or decrease the effect of another drug by
changing its site of action.
• Accordingly, two situations, antagonism or synergism, may occur.
DRUG INTERACTIONS
Interactions in the same direction
➢ Additive effect (Summation)
➢ Synergism and potentiation
❑ Opposite interactions
➢ Antagonism
• Chemical
• Physiological
• Pharmacological
➢ Pharmaceutical incompatibility
Result of drug interaction:
- Increases the effect
- Decreses the effect
-A new effect appears
TYPES OF INTERACTION
Additive effect: 1 + 1 = 2
Synergistic effect: 1 + 1 > 2
Potentialization: 1 + 0 = 2
Antagonism: 1 – 1 = 0 or 0.5
Antagonism:
• When a drug (antagonist) prevents or eliminates the effect of another
drug (agonist), this is called antagonism.
• This reaction is used in cases of poisoning with various drugs and
poisons. (antidote, antidote)
Antagonism: 1 – 1 = 0 or 0.5
2. Pharmacokinetic interactions
3. Pharmaceutical interactions
• When one drug changes the
absorption, distribution,
metabolism and excretion of
another drug, it is called a
pharmacokinetic drug
interaction.
• Medicines can interact outside the
body even before they enter the
body. This is also called
incompatibility.
• Example: Precipitation or color
change occurs when two drugs in
liquid form are mixed.
• These types of drugs should not
be administered together at the
same time, and mixing two drugs
in the same syringe should be
avoided.
• For example, during the
treatment of tetracycline and
ampicillin, the effect of oral
contraceptive (contraceptive)
drugs decreases and unwanted
pregnancy may occur.
FACTORS AFFECTING DRUG INTERACTIONS
Dose
Route of administration
Characteristics of concomitant
drugs
Patient characteristics
Drugs that most frequently cause
interactions in the emergency
department:
• Theophylline
• Macrolide group antibiotics
• Digital glycosides
• Nonsteroidal anti-inflammatories
• ACE inhibitors
• Calcium channel blockers
CHANGES IN SENSITIVITY TO DRUGS
• ❑ Tolerance
• ❑ Tachyphylaxis
• ❑ Addiction
• ❑ Drug allergy
TOLERANCE:
TASIFLAXY:
• It is the gradual decrease in the
potency of a drug after a certain
period of use or congenital
insensitivity of individuals to a
drug.
• It is a situation where tolerance
emerges quickly.
• It occurs over a period of
minutes measured by successive
administration of drug doses.
• Tolerance to morphine
• Meperidin
• metadon
ADDICTION:
• With continuous or periodic
intake of drugs or substances
that have the potential to cause
addiction, an irresistible physical
or psychic desire for that drug /
substance and the occurrence of
withdrawal / withdrawal
symptoms in the absence of the
drug is called "substance
addiction".
DRUG ALLERGY:
• It is a situation in which a drug
produces unusual effects in the
person as a result of
immunological reactions.
• Drug allergy is not related to the
dose applied!!
• Personal sensitivity and drug
structure play an important role
in allergy.
An 18-year-old female patient is brought to the
Which of the following routes of administration is
Drug A is a weakly basic drug with a pKa of 7.8.
If administered orally, at which of the following
sites of absorption will the drug be able to readily
pass through the membrane?
the most desirable for administering the antidote
• A. Mouth (pH approximately 7.0)
for the drug overdose?
• B. Stomach (pH of 2.5)
• A. Intramuscular
• C. Duodenum (pH approximately 6.1)
• B. Intravenous
• D. Jejunum (pH approximately 8.0)
• C. Oral
• E. Ileum (pH approximately 7.0)
emergency department due to drug overdose.
• D. Subcutaneous
• E. Transdermal
Which of the following reactions represents
Phase II of drug metabolism?
• A. Amidation
• B. Hydrolysis
• C. Oxidation
• D. Reduction
• E. Sulfation
All are criteria for selection of essential drugs
EXCEPT
A. Pattern of prevalent diseases
• B. The training and experience of available
• personnel
• C. Treatment facilities
• D. Relative efficacy, cost, and suitability
• E. Latest drug in the market