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‘Pharmacology’ may be defined as—‘the science that essentially deals with the origin,
nature, chemistry, effects, and uses of drugs; it includes: pharmacognosy,
pharmacokinetics, pharmacodynamics, pharmacotherapeutics, and toxicology’.
In fact, the actual usage of drugs, as early remedies, to treat various human ailments has undergone a sea change since the early civilization. However, today’s pharmacology is
entirely based upon absolutely critical scientific evidences supported by meticulously systematic
research in place of the age-old anecdotal information(s). Nevertheless, the twentieth century
witnessed the remarkable discovery of a host of ‘Newer Drug Molecules’ that has virtually
revolutionized the prevailing medical-care system globally. It has ultimately evolved a
prerogative ‘rational system of laws’ that predominantly governs various such functionalities
as:
ä manufacture of drug substances,ä proper storage conditions, andä adequate distribution net-work, in order to accomplish much desired protection to the patients.
However, under the stringent guidelines promulgated by United States Food and
Drug Authority (US-FDA) and World Health Organizations (WHO)—all new drug
substances essentially require substantial evidential proof that they are ‘indeed quite effective’,
reasonably safer, fairly nontoxic, and having fewer side-effects, before they may be duly
recommended and approved for marketing.
To understand the realistic meaning of ‘pharmacology’ one may have to get a clear concept
in mind about the following terminologies, namely:
(a) Pharmacognosy: It refers to the branch of pharmacology dealing with natural drugs
Schmidt a German physician, has duly made use of the terminology ‘Pharmacognosis’
in the monograph entitled Lehrbuch der Materia Medica i.e., Lecture Notes on Medical
Matter, which dates back to 1811. In fact, this compilation exclusively deals with the medicinal
plants and their corresponding characteristics.*
(b) Pharmacokinetics: Pharmacokinetics designates the movement of drugs in the
body over a certain stipulated period of time, including essentially the processes of absorption,
distribution, localization in tissues, biotransformation, and excretion. In other words, it refers
to the manner the body affects the ‘drug substance’ within a certain time frame.
(c) Pharmacodynamics: Pharmacodynamics relates to the study of the biochemical
and physiological effects of drugs and the ensuing mechanisms of their actions, including the
correlation of their respective actions, and effects with their chemical structure i.e., the overall
effects of the ‘drug substance’ on the body.
(d) Pharmacotherapeutics: Pharmacotherapeutics refers to the ‘application of drugs
in the prevention, control, and treatment of diseases’.
It essentially comprises of two distinct classifications, namely: (i) Empirical Pharmacotherapeutics: Empirical pharmacotherapeutics usually
represents certain rare instances, wherein it is not so easy to elicit definite pharmacological
reasons for certain types of drug action. Nevertheless, a specific drug substance is employed
both effectively and successfully to cure some human ailments. Interestingly, it largely finds
its true existence to the so called ‘Folk Medicines’ in the Ayurvedic, Unani, Chinese, Egyptian,
Tibetan, and Greek systems of medicine.
(ii) Rational Pharmacotherapeutics: Rational pharmacotherapeutics refers to
the ‘critical selection of drug(s) exclusively on the basis of logical scientific
explanation that may be accepted globally’. However, in this particular instance one may
safely put forward and seek out various plausible and possible explanations of ‘drug action’
right from the very initial stage to the fag end.
Example: Adrenaline (or epinephrine) used in bronchial asthma.
(e) Pharmacogenetics: Pharmacogenetics** designates ‘the study of the relationship
prevailing between the genetic factors and the nature of responses to drugs’.
Example: Primaquine (an ‘antimalarial drug’) induced hemolysis in such specific
patients with glucose-6-phosphate dehydrogenase deficiency. (f ) Pharmacogenomics: Pharmacogenomics refers to the ‘individual variation of
drug action solely based on the genome*** of the body’.
* Kar, A: Pharmacognosy and Pharmacobiotechnology, New Age International, New Delhi,
** Pharmacogenetics: It refers to the study of hereditary variations in organisms that are revealed
*** Genome: It is the total genetic composition of a cell or organism involving both expressed and
In other words, it concerns with an ‘advanced branch’ particularly related to the
genetic differences in various patients with regard to a drug substance.
(g) Pharmacometrics: Pharmacometrics refers to the ‘branch of pharmacology,
dealing specifically with the screening and comparative quantitative as well as
Chapter 1
qualitative evaluation of drug substances’.
(h) Immunotherapy: Immunotherapy represents the passive immunization of an
individual by administration of preformed antibodies (serum or gamma globulin) actively
produced in another individual; by extension, the terminology has come to include the use of
immunopotentiators i.e., replacement of immunocompetent lymphoid tissue viz., bone
marrow or thymus etc.
(i) Immunopharmacology: Immunopharmacology refers to ‘the specific branch of
‘pharmacology’ that critically deals with the study of the various immunological
aspects of drug action’.
It usually embraces such effects of the ‘drug substance’ that particularly affects the
immune system of the body.
(j) Clinical Pharmacology: Clinical pharmacology designates such ‘drug substances’
that are ultimately prompted to cure human ailments. In other words, the planned scientific
investigative studies on the effects of ‘drug substances’ for the effective treatment in humans
is also referred to as clinical pharmacology.
(k) Clinical Pharmacokinetics: Clinical pharmacokinetics refer to the ‘application
of pharmacokinetics to the safe, and effective therapeutic management of an
individual patient’.
(l) Toxicology: Toxicology essentially deals with the science or study of adverse effects
of chemicals on living organisms.
It may also be regarded as the science specifically dealing with the adverse effects of ‘drugs’ and study of ‘poisons’. One may usually look at the ‘poisons’ as absolutely dangerous
and harmful substances that are proved to be ‘fatal’ to the living organisms. Nevertheless, it
is quite difficult to differentiate the ‘drug’ and ‘poison’ distinctly because any drug substance
may be declared as poisonous when:
ä not employed according to the stipulated directives properly, and
ä used inadvertently at toxic dose levels.
(m) Clinical Pharmacy: Clinical pharmacy refers to the practice of pharmacy wherein
the patient needs are emphasized. It may also be termed as the ‘patient-oriented pharmacy
practice’. Valuable and useful informations and recommendations are duly provided to the
crucial physician/health-care team, but not directly to the patient.
(n) Clinical Privileging: Clinical privileging designates the exact process of
reviewing a practitioner’s credentials for the very purpose of granting and delineating
the scope of clinical privileges.
(o) Clinical Trial: The clinical trial tests are duly conducted so as to ascertain the
effectiveness of newer medicines (drugs), medical devices,* surgeries, or other medical
procedures** in order to prove and establish their ultimate safety and uncompromised
efficacy.
(p) Clinical Trial Phase-I i.e., such investigative studies that essentially involve a
relatively small group of people so as to test the safety and dosage of the drug.
(q) Clinical Trial Phase-II i.e., the studies continuing to test the effectiveness of the
drug as well as its potential side effects.
(r) Clinical Trial Phase-III i.e., such elaborated large-scale intensive studies to test
the effectiveness of the drug as well as the potential side effects.
(s) Clinical Trial Phase-IV i.e., the investigative critical studies that invariably con-
centrate intimately upon the possible new indications or long-term effects of the drug.
A plethora of evidences based on ancient documents and medieval literatures amply indicate
that suffering humans have been duly treated with both physical and mental diseases having
certain kind of ‘folk medicines’ for many thousands of years. With the passage of time the
world witnessed the profuse and abundant usage of all the so-called major systems of
medicine without paying any heed to their over-emphasized philosophical promises.
Examples: A few such typical examples are cited below:
ä Western Medicine—having roots in Egypt and Mesopotamia, and
ä Unani [Islamic] and Ayurvedic [Hindu] Systems—having origins in Western
Asia, Indian Subcontinent, and the Orient viz., China, Japan, Tibet etc.
Importantly, the wealth of accumulated ‘oral transmission of invaluable medical
informations’ was meticulously transformed into well documented written copious volumes
of highly useful ‘books’, such as:
ä Egyptian Papyrus Ebers C. 1600 BC***,
ä Long Pharmacopoeia (1618) and First-British Pharmacopoeia (1864),
ä Chinese Medicinal Plants (4th Century BC),
ä Ayurvedic Medicine (Ayurveda 2500-600 BC), and
ä Unani Medicine (Kitab-Al-Shifa, the Magnum Opus of Avicenna, 980-1032
* Medical Devices—such as: contact lenses, hearing aids, pace-makers, artificial knee joints,
** Medical Procedures, e.g., Robotized Bye-Pass Heart Surgery, Laser-beam based non-abrasive
*** From Ashurbanipal’s Library, but now in the British Museum (London, UK).
ä de Materia Medica (by Dioscrides in First Century AD)*
ä Paracelsus (1493-1541)—challenged the gospel teachings of Galen’s** vast writing.
Chapter 1
Considerable and remarkable advancements in ‘pharmacy’ and ‘chemistry’ were distinctly
accomplished with a big bang during the Seventeenth to Eighteenth centuries. Claude Bernard
(1813–1878), a French physiologist amply proved and advanced critical knowledge with respect
to the actual modus operandi of ‘drug substances’ in the human body, and doctrined that
‘certain drugs do possess specific sites of action within the body’. He meticulously
explored the wonderful logical and convincing field of ‘Experimental Pharmacology’ on
account of his enormous usage of laboratory methods in the exhaustive study of drugs.
Apothecaries (i.e., early pharmacists) from Great Britain started settling in America in the
Eighteenth century to provide reasonably better compounded vis-a-vis herbal preparations in
place of the so called traditional ‘kitchen medicine’, ‘domestic medicine, and ‘home
remedies’.
Incidentally, during the same era United Central and South America together with the Europe have had several pharmacy and dispensary owned by qualified Physicians., who not
only prescribed, prepared, and dispensed drugs but also imported quite a few of them from
England.
The ‘Pharmacopoeia of the United States’*** i.e., the United States’ very First
Official Listing of Drugs, saw the light of the day in 1820.
The 1850s onwards, witnessed a visible change in Pharmacology i.e., a scientific discipline
led by a historical movement under the command of Oswald Schmiedeberg (1838-1921) at the
University of Strasbourg in Germany.
Important Historical Events—that eventually took place between 1847 and 1845 are as
stated under:
Ignaz Philip Semmelweis (1847) : Helped reduce death caused due to Puerperal
fever in maternity wards.
Joseph Lister (1860s)
: Introduced ‘antiseptics’ in surgical procedures
e.g., carbolic acid (phenol).
* Provided a major influence on the European Pharmaceutical knowledge until, the 16th century.
** Galen’s—writing was based on Hippocrate’s ideas of empirical learning, who advocated the philosopy
of ‘humors’ in medicine, and the use of drug mixtures or portions for the cure of various human
diseases.
*** USP: Published by the Massachusetts Medical Society having due approval from the National
Convention of Physicians.
Paul Ehrlich (1907)
: Introduced Arsphenamine [or Salvarsan(R)]
to treat syphilis.
Sir Frederick Banting (1923)
: Introduced ‘Insulin’ (a hormone) for effective
Gerhardt Domagk (1935)
: First Sulpha drug ‘Prontosil’ introduced.
Sir Alexander Fleming (1945)
: Introduced the world famous ‘antibiotic’ peni-
cillin drugs at St. Mary’s Hospital in London
(UK).
Contemporary pharmacology may be defined as—‘a scientific discipline solely based
upon the systematic research to determine and establish ultimately the origin, nature,
chemistry, effects and therapeutic applications of drugs’.
Transmitter
Hormones
substances
Endocrine
A few drugs
block transmitter
inactivation
Some drugs inhibit
transport processes
Some drugs inhibit
Ion Channels
messengers
Fig. 1.1 Prevalent Principles of Drug Action in a Human Body
Interestingly, the present tremendous phenomenal growth of pharmacologic knowledge has been progressively and largely stimulated by the development of ‘advanced medicinal
chemistry’, that ultimately gave rise to a number of newer tools and led to the development
of newer therapeutic agents.
Chapter 1
Fig. 1.1 illustrates the prevalent means whereby a ‘drug’ may produce its effects in the
From Fig. 1.1 one may have a clear vision, knowledge, and understanding of the various 1. Non-specific drug action e.g., Osmotic diuretics (trometamol, mannitol, urea),
activated charcoal that mostly exert their action due to their physicochemical
properties.
2. Transport systems (bottom right hand side) e.g., certain drugs act usually as ‘false
substrates’ or inhibitors for some transport systems viz., Ion-channels
(Ca2+-channels, for instance: Ca2+-channel blockers or Na+ channels, such as: local
anaesthetics).
3. Enzymes (bottom left hand side) e.g., cyclo-oxygenase (COM), monoamine oxidase
(MAO), carbonic anhydrase, and acetylcholinesterase.
4. Receptors e.g., specific protein molecules on which the drugs produce their effects,
and they invariably respond to the endogenous chemicals present in the body.
5. Transmitter substances (top left hand side) e.g., acetylcholine* (ACh) gets
released from the motor nerve endings, and it duly activates receptors strategically
located in the skeletal muscle which in turn triggers off a sequence of events that
ultimately results in the contraction of the muscle.
Other examples included are, namely: norepinephrine, dopamine, serotonin,
γ-aminobutyric acid (GABA), and glutamic acid.
6. Second Messengers (lower Fig.) i.e., activation of receptors either by an agonist
or hormone is duly coupled to the corresponding biochemical or physiological
responses by the help of the ensuing transduction** mechanisms that usually
produce such molecules are known as ‘second messengers’.
7. Affinity i.e., the critical interaction between a ‘drug’ and the subsequent ‘binding
site’ of the receptor solely depends upon the complementarity of a perfect ‘fit’ of the
two molecules. The greater the closeness of the ‘fit’ plus the greater the exact number
of non-covalent bonds, the stronger would be the ultimate resulting attractive forces
prevailing between them; and, therefore, higher the affinity of the ‘drug’ for the
‘receptor’.
8. Specificity i.e., the overall ability of a particular drug to combine with one specific
type of receptor is usually termed as ‘specificity’.
Note: In true sense, no drug is found to be absolutely specific but may possess a
comparatively more ‘selective action upon one particular kind of receptor’.
* Acetylcholine [ACh]: ACh or drugs which specifically activate receptors and produce a
response are termed as agonists.
** Transduction: Transfer of genes between organisms by bacteriophages.

Source: http://www.newacademicscience.co.uk/samplechapter/000015.pdf