Pharmacology

Definition :
The study of drugs and medicines is called
pharmacology.
Pharmacology deals with:
 History
 Source
 Physical & Chemical properties
 Compounding
 Biological & Physiological effect
 Mechanism of action
 Absorption
 Distribution
 Biotransformation
 Excretion
 Therapeutic or other use
of drug

Branch of Pharmacology:
Two main branch of Pharmacology are-
 Pharmacokinetics
 Pharmacodynamics
Pharmacokinetics:
The study of movement and alteration of drugs in the human body. It
deals with-
 Absorption
 Distribution
Metabolism
Excretion

Pharmacodynamics:
The study of action and effect of drugs on the human body. It deals
with-
 The effect of drugs
 The mechanism of action.
(Pharmacokinetics)
What body does to the drug?
Man Drug
What drug does to the body?
(Pharmacodynamics)
Relationship between man and drug

Drug:
A drug is an active ingredient of a medicine.
“Any substance or product that is used or intended to be used to modify or explore
physiological system or pathological states for the benefit of the recipient is called
drug” (WHO-scientific group)
Medicine:
A medicine consists of one or more active
ingredients and excipients.
• Excipients are inert substance used to deliver the drug in a stable
form and to facilitate administration.(coloring, flavoring, sweetening
agents, etc.).

Prodrug:
Drugs that relay on metabolic conversion within the body into their
active form are called prodrug.
Metabolism
Prodrug Drug
(Inactive form) (Activeform)
Placebo:
A harmless, inert substance is given as medicine to satisfy the patient’s
desire for drug therapy, is called “placebo”

Dose:
The quantity of drug or medicine to be administered at one time
(plural-doses).
Dosage:
Size, frequency and number of doses and route of administration –
all together makes the dosage regimen.
Dosage form:
In which form medicines to be administered or available. e.g.:
Tablet, Capsule, Syrup etc.

Types of dosage form:
a. Solid dosage form: Tablet, Capsule, Suppository etc.
b. Liquid dosage form: Syrup, Suspension, Solution, Injectable etc.
c. Semisolid dosage form: Cream, Ointment, Gel etc.
d. Gaseous dosage form: Inhaler, Spray.

Route of administration:
 Enteral or alimentary route-
 Oral: Most common
 Sublingual: Drug placed under the tongue, where it dissolved.
 Buccal: Pertaining to the cheeks.
 Rectal: Can be used when drug objectionable taste.
 Trans lingual: on the tongue.
 Parenteral route-
Intra muscular (IM)
Intra venous (IV)
Intra-arterial (IA)
Intra-cardiac
Intra-thecal

Intradermal (Intra cutaneous )(IC)
 Subcutaneous route (Hypodermic)
Intraosseous- into bone marrow
Intra pleural
Intraperitoneal (IP)
Intra-articular(IArt)
 Others :
 Inhalation
 Intranasal
 Topical
 Transdermal
 Ocular/Ophthalmic

Different types of dose
Therapeutic or Effective Dose
The dose which will bring about the desired effect in 100% of the
population tested.
Median Effective Dose (ED50)
The dose which will produce a desired effect in 50% of the population
tested.
Lethal Dose :
The dose which will cause death in 100% of the animals under
experiment.

Median Lethal Dose (LD50 )
The dose which will cause death in 50% of the animals under
experiment.
Maximal (maximum) Dose :
The largest dose which can be tolerated by the patient before
serious side effects occur.
Minimal (minimum) Dose :
The smallest dose which is required to produce certain desirable
effect.
Prophylactic Dose :
The dose which prevents the body from being attacked with a
disease or diseases.

Maintenance Dose:
Dose required for maintaining the desired effect that is achieved by
preceding dose.
Adult Dose:
According to British Pharmacopoeia , the dose in between 20 to 60
years of age is known as adult dose .
Pediatric Dose:
The determination of the correct amount, frequency, and total
number of doses of a medication to be administered to a child or
infant.

Therapeutic Index (Safety Index)
The ratio of the median lethal dose (LD50) to the median effective
dose (ED50)
TI=
LD50
ED50
It is an approximate assessment of the safety of drug.
More T.I , more safety and vice versa, For example-
Chemotherapeutic Drugs:
LD50= 16, ED50 = 4 . So T.I= 4 So, the chemotherapeutic drugs are more safe
Anti-cancer drugs: than the anticancer drugs
LD50=16, ED50=8 . So T.I = 2

Tablets After
swallowing
Disintegration Dissolution
AbsorptionDistribution
Therapeutic Effect(By its
own mechanism of
action)
Metabolism
Excretion (By
different route)
Pharmacokinetics of Tablet

Capsule After
swallowing
Dissolution Absorption
Distribution
Therapeutic Effect(By its
own mechanism of
action)
Metabolism
Excretion (By different route)
Pharmacokinetics of Capsule

Disintegration
The process of breakdown of any solid dosage forms into smaller
particles is known as Disintegration.
Disintegration Time
The time required for Disintegration is known as Disintegration Time
(DT).

Dissolution
Dissolution is the process by which a solute forms a solution in a
solvent
Dissolution rate
The rate at which the granules or fine particles of any solid dosage
form go into solution before being absorbed into the GIT is known as
Dissolution rate

Absorption
The rate at which drug molecules cross the cell membrane to enter
into the body for (systemic circulation) is called absorption.
 Most of the oral drugs are absorbed to the extent of around 75% in
1-3 hours.
Process of drug absorption :
 Simple Diffusion
 Facilitate Diffusion
 Active Transport

Rate of absorption depends on :
• Route of administration
• Solubility
• Gastrointestinal motility
• blood flow
• Particle size and formulation
• Chemical factors

Drug distribution
Drug distribution is the process by which a drug reversibly leaves
the blood stream and enters the extracellular fluid and the cells of
the tissue .
Drug distribution depends on following factors-
 Permeability across the tissue barriers.
 Binding within compartments
 pH of distribution media
 pKa of drug molecule.
 Regional blood flow.
 Fat : water partition.

Volume of distribution -
It is defined as the volume of fluid into which a drug apparently
distributes. It is commonly known as apparent volume of distribution
and expressed as Vd.
The higher is the Vd, the more extensively it is distributed in the body
tissues.
Examples:
Spiramycine : 268-516 litres/70kg
Perfloxacine : 94-117 litres/70kg (single 400mg tab)
Ciprofloxacin : 140-210 litres/70 kg

Protein binding
In the blood, a proportion of the drug has to be bound to different
plasma proteins, especially albumin. This binding is known as protein-
binding(PB).

 Protein Bound considered significant when it is 90% & above.
 When two or more significantly higher protein- bound drugs are
taken together, there may be significant changes in drug
distribution and hence, may cause therapeutic hazards.
Drugs with high PBs include:
Paracetamol – Tolbutamide = Hypoglycemic shock
Aspirin – Warfarin (anticoagulant) = Hemorrhage

Mechanism of drug action:
Drugs can act in the three major ways :
 by direct physical and chemical action
 by combination with specific receptors
 by alteration of physiological enzyme processes (interferes with
enzyme’s action)

Receptor –
A receptor is a specific macro-molecule to which a specific group of
drugs or hormones or neurotransmitters can bind.
Types of receptor:
 Intracellular receptors
 Ligand -gated ion channel
 G protein – coupled receptors
 Enzyme – linked receptors

Affinity:
Tendency of drug to bind with receptor is termed as affinity .
Efficacy:
Efficacy is the ability of drug to produce a desire amount of effect
after binding a receptor .
Potency:
Comparative measure of different doses of two drugs that are
needed to produce the same effect is called potency .

Drugs that interact with receptors can be classified as:
 Agonist
 Antagonist
Agonist
A substance that binds with a receptor and elicits a cellular response.
Agonist can be further divided into two types…
 Full agonist (Bring maximal or full response)
 Partial agonist (Does not produce maximal effect)

Antagonist
A substance which binds with a receptor but blocks the action of
agonist. Antagonist are subdivided into three types-
 Competitive antagonist
 Noncompetitive antagonist
 Uncompetitive antagonist

Metabolism
Biochemical alteration of food & drugs inside the body is called
metabolism. Metabolism is also known as Biotransformation.
 The liver is the principal organ of drug metabolism.
Other organs include :
 Gastro-intestinal tract
 the lungs
 the skin
 the kidney
 the plasma
 the skeletal muscle

First Pass metabolism
Metabolism of drug before entering into the systemic circulation is
called first pass metabolism.

It is the act of elimination of systemically absorbed drug(s) and waste
materials from the body.
 Kidney is the most important organ of excretion.
Drugs may also be excreted in :
Bile Sweat
Saliva Gastric juice
Lungs (expired air) Breast milk
Tears Hairs and Nails
Excretion

Bioavailability
The rate and extent to which the active ingredient is absorbed and
becomes available to the site of drug action is known as Bioavailability
(US FDA).
Rate means onset and intensity of drug action
Extent means amount of drug absorbed and duration of action
 Bioavailability of a drug is represented by percentage(%).

 When drug given intravenously (IV), the bioavailability of any
drug is 100%.
 For orally administered drugs bioavailability is usually less than
100%.

Half life
It is the time taken for the plasma concentration of a drug in the body
to be reduced by 50% of initial level. It is also called Plasma half life.
 It is expressed as t1/2 .
 It is generally believed that, the higher is the half-life the longer is
the duration of action.

Effects of Drug
 Therapeutic effect: Desired or beneficial effect.
 Adverse effects.
 Side effects.
 Untoward (unwanted) effect:
 Qualitative:
 Idiosyncrasy
 Hypersensitivity
 Quantitative(e.g. Drug intolerance)
 Toxic effect

Adverse effects:
Harmful or seriously unpleasant effects occurring at therapeutic dose
range and which call for reduction of dose or withdrawal of the drug
and forecast hazard from further administration.
Side effects:
Therapeutically undesired and unavoidable effects that occur
associated with beneficial effect at the normal therapeutic dose of a
drug is called side effect .
Toxic effects:
Unwanted effect due to toxic dose is called toxic effect. e.g.:
Chloramphenicol: Aplastic anemia.
Streptomycin :8th cranial nerve damage.

Hypersensitivity:
It usually refers to allergic or other immunologic responses to
drugs.
Idiosyncrasy:
Inherited abnormal responses to drugs (usually due to genetic
abnormality) are known as idiosyncrasy, e.g., porphyria.
Teratogenicity:
Induction of fetal malformation by a drug due to its
administration to mother during pregnancy is known as
teratogenicity and the drug causing this effect is known as a
teratogenic drug.

Drug combination or combination therapy
Defined as the use of 2 or more drug separately or in a fixed-dose.
Effect of drug combination:
 Summation or addition (additive) –
When the combined action of two drugs is equal to the arithmetic sum
of the effects of the individual drugs; i.e., 2+2 =4.
Example include :
In Hypertension Beta-blockers + Diuretics = additive action

 Synergism (super additive) –
The combined action of two or more drugs could be greater than
simple addition of individual drug effects
i.e. 2+2 > 4
Example include :
sulfamethoxazole + Trimethoprim = co-trimoxazole
 Drug antagonism -
Antagonisms occur when the action of one drug opposes the action of
another.
Examples include:
In morphine overdose : Morphine + Naloxone (morphine antagonist)

Indication:
Name of the disease against which specific drug to be used.
Contraindication:
Condition in which particular drug cannot be prescribe.
Precaution :
In which situation before treatment , dose to be adjusted after
monitoring the patient .
Pregnancy category:
It is an assessment of the risk of fetal injury due to the drug
administered by mother during pregnancy .

 Category A: Studies show no risk or find no evidence of harm
in pregnant women.
 Category B: Animal studies show no risks, but there are no
studies on pregnant women.
 Category C: Animal studies have shown risk to the fetus, there
are no studies in women, or studies in women and animals are
not available.
US FDA Pregnancy category explained

 Category D: There is positive evidence of potential fetal risk, but
the benefits from use in pregnant women may be acceptable
despite the risk (i.e. life threatening condition to mother)
 Category X: Studies in animals or human beings have
demonstrated fetal abnormalities, or there is evidence of fetal
risk. The drug is contraindicated in women who are or may
become pregnant.

Pharmacopoeia
Is an authorized treaties on drug and their preparation, especially a
book containing formulas and information that provides a standard for
preparation and dispensing of drugs .
British Pharmacopoeia (BP)
United States Pharmacopeia (USP)
British National Formularies (BNF)
European Pharmacopoeia (EP)
Indian Pharmacopoeia (IP)
World Health Organization Pharmacopoeia (WHOP)
Bangladesh National Formulary (BDNF)

Official drugs:
Official drugs are those drugs which are included in pharmacopoeia
Over the counter drugs (OTC):
Those drugs which are available without prescription are called OTC
drugs. E.g. Paracetamol, vitamin tablet, Iron tablet.
Prescription drugs:
Those drugs which are available with prescription are called
prescription drugs. These include majority of drugs which are
prescribed by registered physician
Control drugs:
Control drugs are those drugs which can never be prescribed without
prescription as they can be abuse. e.g. pethidine, morphine

Drug Tolerance:
Gradual diminution of tissue response to a drug due to repeated
administration is called tolerance.
Stages of Tolerance:
Habituation Addiction Dependence Tolerance
Drug Habituation:
Condition resulting from repeated consumption of certain drugs,
characterized by psychologic dependence. e.g.: Tobacco, Caffeine

Dependence:
Dependence is a condition in which the body has adjusted to the
presence of a drug, resulting in clear symptoms of withdrawal when
its use stops.
Addiction :
Drug addiction is a pathological or abnormal condition which arise
due to frequent drug use .

Drug nomenclature
Any drug may have names in all three of the following classes:
 Chemical Name
 Generic Name
 Brand Name Chemical Name :
 Full chemical name describes the compound,
 It describes the structure of the drug
 It is unsuitable for prescribing .

Generic name:
The assigned name of drug by which it will be known throughout the
world no matter how many different companies manufacture it. This
name is usually assigned and agreed upon by the AMA (American
Medical Association) council of drug and the World Health
Organization (WHO)
Generic names are chosen by official agencies:
BAN : British Approved Names
INN : International Non-proprietary Name
USAN : United Sates Approved Name
FDA : Food and Drug administration.

Trade name/Brand name:
The name that is given by particular
company for marketing the drug.

Area under the curve (AUC)

Minimum Effective Concentration (MEC):
It is defined as the minimum concentration of drug in plasma required
to produce the therapeutic effect.
Onset of action (OA):
This is the time required to achieve the drug concentration in MEC
level.
Termination of action (TA):
When the drug is no more able to exert any action i.e. When the
plasma concentration of the drug falls below the minimum effective
concentration (MEC)

Duration of action (DA) :
The time elapsing between the onset of action and the termination of
action of a drug is the duration of action (DA=TA-OA)
Peak concentration Cmax :
The highest level of concentration achieved in the plasma following the
administration of a single dose.
Trough concentration :
The lowest concentration of drug found in the plasma immediately
before the next dose is given .

Rx -- (you) take
Ac - ante cibum -- before meal/food
Pc - post cibum -- after meal/food
Bid - bis in die -- twice daily
Tid - ter in die -- thrice daily
qid - quater in die -- four times daily
q6h - -- every 6 hourly
qd - quaque die -- every day
c -- cum (with)
IV -- intravenous
IM -- intramuscular
Important Abbrevision :

noct -- at night
hs -- at bedtime
po -- by mouth
pv -- through vagina
p.r.n - pro re nata -- when necessary
sos -- if necessary
stat -- immediately
supp -- suppository
susp -- suspension
tsp -- teaspoonful (5 ml)
Important Abbrevision :

Adnan-Ul-islam
B.Pharm. (R.U)
adnan.ru.bd@gmail.com