1. Introduction to Pharmcology and
Md. Nafizur Rahman
Dept. of Genetic Engineering & Biotechnology,
Shahjalal University of Science & Technology, Sylhet.
Pharmacology is the branch of biology concerned with the study of drug action, where a
drug can be broadly defined as any manmade, natural, or endogenous (from within body)
molecule which exerts a biochemical and/or physiological effect on the cell, tissue, organ,
or organism. The field encompasses drug composition and properties, synthesis and drug
design, molecular and cellular mechanisms, molecular diagnostics, interactions etc.
The two major divisions of pharmacology are pharmacodynamics and pharmacokinetics.
The former studies the effects of the drug on biological systems, and the latter the effects
of biological systems on the drug.
Pharmacognosy is systematic study of the crude drugs obtained from natural origin like
plant, animal and minerals. The American Society of Pharmacognosy defines
Pharmacognosy as –
″the study of the physical, chemical, biochemical and biological properties of drugs, drug
substances or potential drugs or drug substances of natural origin as well as the search for
new drugs from natural sources. ″
3. Branches of pharmacology
(what the drug does to the body)—it is a branch of pharmacology that deals with the
mechanism of action, pharmacological effects, indication and contraindication of use and
adverse effects of drugs.
(what the body does to the drug)—it is the branch of pharmacology that deals with drug
dose, routes of administration and absorption, distribution, metabolism and excretion.
Clinical pharmacology is the basic science of pharmacology with an added focus on the
application of pharmacological principles and methods in the medical clinic and towards
patient care and outcomes.
Posology is the study of how medicines are dosed. This depends upon various factors
including age, weight, sex, elimination rate of drug and time of administration.
Pharmacotherapeutics is the medical science concerned with the use of drugs in the
treatment of disease. It explains the mechanisms and effects of drugs on the body and the
relationship between dose and drug response.
Pharmacy is the science and technique of preparing and dispensing drugs including
collection, identification, purification, isolation, synthesis, standardization and quality
control of medicinal substances.
The area of pharmacology that focuses on the effects of drugs on patient safety.
According to WHO pharmacovigilance is ‘the science and activities relating to the
detection, assessment, understanding and prevention of adverse effects or any other
possible drug related problems’.
Toxicology is concerned not only with drugs used in therapy but also with the other
chemicals that may be responsible for environmental or industrial intoxication.
5. Scope of Pharmacognosy
Pharmacognosy has vast applications in the Pharmaceutical Industry and therapeutics.
Pharmacognosy is important branch of pharmacy which is playing key role in new
drug discovery and development by using natural products.
It is an important link between modern medicine systems (allopathy) and traditional
system of medicine.
It is acting as bridge between pharmacology, medicinal chemistry, pharmaceutics and
The drug-drug, drug-food interactions are studied in pharmacognosy which help us
avoid the untoward effects of severe interactions and hence help in obtaining the
optimal therapeutic outcomes.
Pharmacognosy includes knowledge about safe use of herbal drugs including toxicity,
side effects, drug interaction thereby increasing effectiveness of modern medicine.
Pharmacognosy is the base for development of novel medicines. Most of the
compounds obtained from natural product serve as prototype or base for
development of new drug which are more active and less toxic.
A substance which is intended for use in the diagnosis, cure, mitigation, treatment, or
prevention of diseases and has efficacy to affect the structure or any function of the body.
According to WHO (World Health Organization) “Any substance or product that is used or
intended to be used to modify or explore the physiological system or pathological state in
the benefit of the recipient’’.
A crude drug is any naturally occurring, unrefined substance derived from organic or
inorganic sources such as plant, animal, bacteria, organs or whole organisms intended for
use in the diagnosis, cure, mitigation, treatment, or prevention of disease.
Drug nomenclature is the systematic naming of drugs, especially pharmaceutical drugs.
Drugs, in the majority of circumstances, have 3 types of names:
1. Chemical names, the most important of which is the IUPAC name;
7. 2. Generic or nonproprietary names, the most important of which are the International
Nonproprietary Names (INNs)
3. Trade names, which are brand names.
There are various systems of chemical nomenclature and thus various chemical names for
any one substance. The most important is the IUPAC name. It states the structure in terms
of atoms and molecules accompanied by a diagram of the chemical structure. For
example, acetyl-p-amino-phenol is for Paracetamol.
This is the abbreviated and approved name of the drug. It is the official medical name
assigned by the producer in collaboration with the Drugs Board and Nomenclature
Committee. The generic names usually indicate via their stems what drug class the drug
belongs to. For example, aciclovir is an antiviral drug because its name ends in the ‘vir’.
8. Proprietary/Trade/Brand Name:
These are names given to the drug by the manufacturing and marketing company and has
a trademark symbol®. The term trade name is a standard term in the pharmaceutical
industry for a brand name or trademark name. In most cases one drug could have so
many trade/ brand names e.g. Acetaminophen has several trade names. Some are
Tylenol, Paramol, Panadol, Capol etc.
Properties of an ideal drug
Effectiveness: It should be non-toxic, bio-compatible, biodegradable and physio-
chemically stable and elicit the responses for which it is given.
Safety: It should not produce harmful effects even if administered in very high doses
and for a very long time.
Uniform distribution: Restrict drug distribution to target cells or tissues or organs
and should have uniform capillary distribution.
Minimal side effect: An ideal should have no side effect. Although the risk of adverse
side effects cannot be fully eliminated; it should be minimal.
9. Minimal loss: An ideal drug should have minimal drug leakage during transit and
cannot be destroyed by other cells or microbes.
Easy to eliminate: The drug and carriers should be easily eliminated from the body
without any problem by simple metabolic processes after its action and no carrier
induced modulation of diseased state.
Easy to administration: It should be simple to administer to enhance patient
compliance and decrease errors.
Free from interaction: This property can reduce drug effects because many drugs are
contraindicated, drug release should not affect the drug action.
Low cost: The preparation of the delivery system should be easy or reasonably
simple reproductive and cost effective.
Sources of Drugs
Until the start of the 20th century, the substances for the treatment of any disease were
obtained from natural sources. Among the natural sources plants were mainly used. Now
a good source of drugs. Some source of drug is given below.
10. 1.Plant source:
The pharmacologically active constituents of plants are grouped according to their physio-
chemical properties and include alkaloids, oils, gums, mucilage, glycosides and
carbohydrates. Different types of plant sources are…
Alkaloids – Atropine, cocaine, morphine.
Oils- Olive oil, castor oil
Gum and mucilage- Agar and psylm
Tannins- Tannic Acid
Almost all parts of the plants are used i.e. leaves, stem, bark, fruits and roots.
Seeds of Nux Vomica give strychnine, which is a CNS stimulant.
Calabar beans give Physostigmine, which is a cholinomimetic drug.
Castor oil seeds give castor oil.
The leaves of Digitalis purpurea are the source of Digitoxin and Digoxin, which are
Leaves of Eucalyptus give oil, which is important component of cough syrup.
Tobacco leaves give nicotine.
Atropa belladonna gives atropine.
Ipecacuanha root gives Emetine, used to induce vomiting as in accidental poisoning.
It also has amoebicidal properties.
Rauwolfia serpentina gives reserpine, a hypotensive agent.
Reserpine was used for hypertension treatment.
Vinca rosea gives vincristine and vinblastine.
Rose gives rose water used as tonic.
Senna pod gives anthracine, which is a purgative (used in constipation)
Calabar beans give physostigmine, which is cholinomimetic agent.
Cinchona bark gives quinine and quinidine, which are antimalarial drugs. Quinidine
also has antiarrhythmic properties.
Atropa belladonna gives atropine, which is anticholinergic.
Hyoscyamus Niger gives Hyosine, which is also anticholinergic.
Chondrodendron tomentosum gives tuboqurarine, which is skeletal muscle relaxant
used in general anesthesia.
Pancreas is a source of Insulin, used in treatment of Diabetes.
Blood of animals is used in preparation of vaccines.
13. Urine of pregnant women gives human chorionic gonadotropin (hCG) used for the
treatment of infertility.
Sheep thyroid is a source of thyroxin, used in hypertension.
Cod liver is used as a source of vitamin A and D.
Anterior pituitary is a source of pituitary gonadotropins, used in treatment of
Stomach tissue contains pepsin and trypsin, which are digestive juices used in
treatment of peptic diseases in the past. Nowadays better drugs have replaced them.
Penicillium notatum is a fungus which gives penicillin.
Actinobacteria give Streptomycin.
Aminoglycosides such as gentamicin and tobramycin are obtained from streptomycis
14. Metallic and Nonmetallic sources:
Iron is used in treatment of iron deficiency anemia.
Mercurial salts are used in Syphilis.
Zinc is used as zinc supplement. Zinc oxide paste is used in wounds and in eczema.
Iodine is antiseptic. Iodine supplements are also used.
Gold salts are used in the treatment of rheumatoid arthritis.
Fluorine has antiseptic properties.
Borax has antiseptic properties as well.
Selenium as selenium sulphide is used in anti-dandruff shampoos.
Petroleum is used in preparation of liquid paraffin.
When the nucleus of the drug from natural source as well as its chemical structure is
altered, we call it synthetic. Examples include Emetine Bismuth Iodide
15. Semi Synthetic Source:
When the nucleus of drug obtained from natural source is retained but the chemical
structure is altered, we call it semi-synthetic.
Examples include Apomorphine, Diacetyl morphine, Ethinyl Estradiol, Homatropine,
Ampicillin and Methyl testosterone.
Most of the drugs used nowadays (such as antianxiety drugs, anti convulsants) are
6.Recombinant DNA technology:
Recombinant DNA technology involves cleavage of DNA by restriction endonucleases.
The desired gene is coupled to rapidly replicating DNA (viral, bacterial or plasmid).
The new genetic combination is inserted into the bacterial cultures which allow
production of vast amount of genetic material.
Huge amounts of drugs can be produced.
Drug can be obtained in pure form.
It is less antigenic.
17. Enteral Administration
The enteral routes of administration are those in which the drug is absorbed from the
gastrointestinal tract. These include the sublingual, oral, and rectal routes.
oral means to administer “by mouth.” The medication is swallowed, and the drug is
absorbed from the stomach and small intestine.
can be self-administered, pain free and easy to take
absorption takes place along the whole length of the GI tract
cheap, compared to most other parenteral routes
Slow absorption slow action – can’t use in emergency
only part of the drug may be absorbed
Irritable and unpalatable drugs- nausea and vomiting
destruction of drugs by gastric acid and digestive juices
unable to use in unconscious patient
18. Sublingual Route:
In sublingual administration, a drug product is placed under the tongue and in buccal
administration, the drug is placed between the cheek and the gum. Both the sublingual
and the buccal routes of administration enable the rapid absorption of certain drugs and
are not affected by first-pass drug metabolism in the liver.
absorption and termination is quick
can be self-administrated
economical, due to low dose required
unpalatable and bitter drugs
irritation of oral mucosa due to high dose
only few drugs can be absorbed
Rectal administration of drugs in suppository form can result in either a localized effect or
a systemic effect. It is useful when patients cannot take medications by mouth.
used in children enema
little or no first pass effect
higher concentrations rapidly achieved
absorption is slow and erratic
irritation or inflammation of rectal mucosa can occur
Parenteral administration refers to drug administration with a needle and syringe or with
an intravenous infusion pump. The most commonly used parenteral routes are the
intravenous, intramuscular, and subcutaneous routes.
Intravenous administration bypasses the process of drug absorption and provides the
greatest reliability and control over the dose of drug reaching the systemic circulation. The
intravenous route is widely used to administer antibiotics and antineoplastic drugs to
critically ill patients, as well as to treat various types of medical emergencies.
desired blood concentrations achieved
high amount of drug can be administrated
avoids first pass metabolism by liver
permits a rapid effect and a maximal degree of control over the circulating levels
first acting route in case of emergency
unlike drugs in the GI tract, those that are injected cannot be recalled by strategies
such as emesis or by binding to activated charcoal
induce hemolysis or cause other adverse reactions by the too-rapid delivery of high
concentrations of drug to the plasma, tissues and vital organs like heart, brain etc.
Thrombophlebitis of vein and necrosis of adjoining tissue if extravasation occurs.
irritation and cellulitis can occur
less safe and possible danger of infection
expensive, less convenient and painful
21. Intramuscular Route:
Intramuscular administration is suitable for treatment with drug solutions and particle
suspensions.Suspensions are often used to extend the duration of action of a drug over
many hours or days.
Absorption reasonably uniform
Bypasses absorption to give an immediate effect
Rapid onset of action
Mild irritants can be given
First pass metabolism can be avoided
Only up to 10ml drug given
Occurrence of local pain and abscess
Can cause nerve damage and also infection
Can cause bleeding if the patient is receiving an anticoagulant.
22. Subcutaneous Route:
Subcutaneous administration is suitable for treatment with drug solutions and particle
suspensions.Solutions are absorbed more rapidly than particle suspensions.
Greater circulation of blood to the muscle
Minimize the risk associated with intravascular injection
Prolonged action of drug
Slow absorption rate of drug
Only small volume can be injected
Cannot be used for drugs that irritate cutaneous tissues
Drug toxicity occurs when a person has accumulated too much of a drug in his
bloodstream, leading to adverse effects within the body.
This can happen if the dose taken exceeds the prescribed dose, either intentionally or
accidentally. However, with certain medications, drug toxicity can also occur as an adverse
drug reaction (ADR). In this case, the normally given therapeutic dose of the drug can
cause unintentional, harmful and unwanted side effects. Additionally, factors such as age,
kidney function and hydration can affect how quickly one’s body is able to clear a
medication from the system. The causes of drug toxicity can be classified in several ways
and include mechanism-based (on-target) toxicity, immune hypersensitivity, off-target
toxicity, and bio activation/covalent modification.
An important class of on-target adverse effects may occur because the drug, or one of its
metabolites, interacts with the appropriate receptor but in the incorrect tissue. Many
drug targets are expressed in more than one cell type or tissue. For example, the anti-
histamine diphenhydramine hydrochloride is an H1 receptor antagonist used to reduce
the unpleasant symptoms of histamine release in allergic conditions.
Diphenhydramine also crosses the blood-brain barrier to antagonize H1 receptors in the
central nervous system, leading to somnolence. This adverse effect led to the design of
24. second-generation H1 receptor antagonists that do not cross the blood-brain barrier, and
so do not induce drowsiness. Off-target adverse effects occur when the drug interacts
with unintended targets. Indeed, few drugs are so selective that they interact with only
one molecular target.
A drug or its metabolites or both interact with specific receptors to mediate ON-TARGET
or OFF-TARGET adverse effects. In addition, metabolites can be detoxified and excreted,
or can react with a variety of macromolecules, including DNA, small antioxidants such as
glutathione(GSH) or cellular or plasma proteins. The formation of unpaired DNA adduct is
often mutagenic and may lead to cancer. The impairment of oxidative defenses can lead
to inflammation and cell death. The formation of drug protein adduct can trigger immune
responses that can damage cells and tissues. Regardless of the mechanism of damage, a
gradation of acute responses from protective to apoptosis and necrosis can result,
depending on the extent of damage and the temporal and dose relationship. Chronic
inflammation and repair can lead to tissue fibrosis.
26. Drug Interaction
A drug interaction is a situation in which a substance (usually another drug) affects the
activity of a drug when both are administered together. This action can be synergistic
(when the drug's effect is increased) or antagonistic (when the drug's effect is decreased)
or a new effect can be produced that neither produces on its own.
Drug interactions fall into three broad categories:
1. Drug-drug interactions
2. Drug-food interactions
3. Drug-condition interaction
Drug-drug interactions are possible whenever a person takes two or more medications
concurrently. If a patient is taking two drugs and one of them increases the effect of the
other, it is possible that an overdose may occur. The interaction of the two drugs may also
increase the risk that side effects will occur. On the other hand, if the action of a drug is
reduced it may cease to have any therapeutic use because of under dosage. The drug
affected by the interaction is called the ΄΄object drug΄΄ and the drug causing the
27. interaction is called the ΄΄precipitant drug΄΄. There are a number of mechanisms by which
drugs interact with each other, and most of them can be divided into two general
categories: Pharmacokinetic and Pharmacodynamic interactions.
Modifications in the effect of a drug are caused by differences in the absorption,
transport, distribution, metabolization or excretion of one or both of the drugs compared
with the expected behavior of each drug when taken individually. These changes are
basically modifications in the concentration of the drugs. In this respect two drugs can be
homergic if they have the same effect in the organism and heterergic if their effects are
different. Effects are-
o Inhibition of Absorption.
o Enzyme Inhibition Increasing Risk of Toxicity
o Enzyme Inhibitors Resulting in Reduced Drug Effect
o Enzyme Induction Resulting in Reduced Drug Effect
o Enzyme Induction Resulting in Toxic Metabolites
o Altered Renal Elimination.
28. Pharmacodynamic Interaction:
The change in an organism's response on administration of a drug is an important factor in
Pharmacodynamic interactions. The well-founded suspicion exists that there are more
unknown interactions than known ones. When pharmacodynamic drug interactions occur,
two drugs have additive or antagonistic pharmacologic effects-
o When two or more drugs with similar pharmacodynamic effects are given, the
additive effects may result in excessive response and toxicity.
o Drugs with antagonistic pharmacodynamic effects may reduce the response to
one or both drugs.
Certain foods and specific nutrients in foods, if ingested concurrently with some drugs,
may affect the overall bioavailability, pharmacokinetics, pharmacodynamics and
therapeutic efficacy of the medications. Foods containing active substances that interact
against certain medications can produce unexpected or adverse effects. Nutrients include
food, beverages and dietary supplements. Consumption of these substances may alter the
effects of drugs the patient takes. For example:
The presence of food in the digestive tract may reduce absorption of a drug. Often, such
interactions can be avoided by taking the drug one hour before or two hours’ after eating.
Dietary fiber also affects drug absorption. Certain vitamins and minerals impact on
medications too. Large amounts of broccoli, spinach and other green leafy vegetables high
in vitamin K, which promotes the formation of blood clots, can counteract the effects of
heparin, warfarin and other drugs given to prevent clotting. Dietary supplements,
including medicinal herbs are products that contain a vitamin, mineral, herb or amino acid
and that are intended as a supplement to the normal diet. They may interact with
prescription or over-the counter drugs. Some dietary components increase the risk of side
Alcohol affects body processes and interacts with many drugs. Alcohol is a drug that
interacts with almost every medication, especially antidepressants and other drugs that
affect the brain and nervous system.
30. Adverse Effect of Drugs on Food and Nutrition
1. Drugs can alter food intake and nutrition status-
appetite increased or decreased, unusual food cravings
metabolic rate increased or decreased
oral side effects e.g. dry mouth/mouth pain
2. Drugs can change nutrient absorption-
Drugs may speed up gut transit; this reduces nutrient absorption from food.
Drugs may slow down gut transit.
Drugs can increase the pH in the stomach
Drugs (e.g. antibiotics) can decrease and alter normal gut flora balance
necessary for the absorption of vitamin K and B vitamins (B1, B2, B6, B12, and
Drugs can bind to nutrients (e.g. bile acid sequestrants impair absorption of fat
soluble vitamins and fat soluble phytochemicals).
Drugs can impair absorption
31. 3. Drugs can change nutrient excretion:
Increase urinary excretion (e.g. Lasix increases losses of sodium, potassium,
chloride, and magnesium, thiamin)
Decrease urinary excretion
4. Drugs can change nutrient metabolism
This interaction tends to occur when a medication has the potential to worsen a disease.
The effect a drug has in certain patients may be unexpected not related to the drug parts
but because of the patient’s disease pattern.