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After reading this essay you will learn about:- 1. Definition of Pharmacology 2. Historical Developments of Pharmacology 3. Stages of History of Development 4. Branches 5. Records.
Essay on the Definition of Pharmacology:
Pharmacology consists of two Greek Words-Pharmakon = Drug and Logos = Study and may be defined as follows:
(i) Pharmacology is the science that deals with drugs.
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(ii) Pharmacology consists of detailed study of drugs, particularly drugs action on living animals, tissues or organs. The action of drugs may be beneficial or harmful.
(iii) Pharmacology is the science in which we study the response of living animals to chemicals or drugs.
(iv) Pharmacology is defined as the study of the effects of drugs on the structures and metabolism of natural tissues.
(v) Pharmacology can be defined as the study of the manner in which the functions of living system is affected or influenced by chemicals.
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(vi) This subject deals with the properties and effects of drugs and in broad sense, it can be defined as the study of interactions between chemical substances and biological systems.
(vii) While defining in broad sense, it includes the knowledge of the history, source, physical and chemical properties, compounding, bio-chemical and physiological effects, mechanism of action, absorption, distribution, metabolism, excretion and therapeutic and other effects of drugs.
Essay on the Historical Developments of Pharmacology:
Diseases are as old as man. Fighting disease with drugs is an endless task that originated from existence of mankind. Drugs have its origin with illness and the later has been associated with evolution. Just imagine about the nomads, the primitive man, who was wanderer, a food gatherer and shelter seeking. There was no concept of family.
There were no clothes, men and women were wandering naked. Gradually the notion of family started and he lived together with so called his family members. If any of them died the pain of death he might have felt. He must have thought about death. Why some person dies? And then fear of death might have occurred to him. He must have started thinking about death/Diseases.
Homosapiens being the intelligent most among the species evolved, based on the principles of “necessity” and “trial” could observe effectiveness of many plants in relief for his pains and sufferings. The primitive (early) history of the causative agents of diseases included wrong Gods, spirits witches and other evil influences.
The form of therapy was incantation, prayer and ceremony designed to appease the evil agents of the diseases. They were using sacrifice of animals, individuals and prayers.
The tribal leaders were known as medicine men or the expert or witch doctors (Ojha), were very powerful men and leader in such all ceremonies. In addition, they had knowledge about certain plants and animal products to be used in the treatment of certain diseases. The first treatise on medicine was undoubtedly the Ayurveda in India and that is at least 500 years ahead of the Greek Medicine.
The medical literature was related to metaphysics, hypnotism etc. and belief in supernatural agencies as the cause and cure of diseases. Thus, in India, this was originally a part of the fourth Veda called the Atharva Veda. The real father of Indian Medicine was Atrya with his distinguished disciples-Agnivesha, Bhala, Jatukarana, parasara, Harita and Ksharapani.
Works of Bhala and Harita are still available in fragments and those of Agnivesha were edited by Charaka which stand unsurpassed as a standard and authoritative book on Ayurveda even to day, other works are yet untraced. The next outstanding personality in Indian medicine was Susrutha whose works stand second to Charaka (a surgeon). He mentioned many instruments and techniques.
Essay on the Stages of History of Development of Pharmacology:
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However, the history of development of pharmacology can be divided into following stages or periods:
(i) Egyptian period
(ii) Greek period
(iii) Medieval period
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(iv) Renaissance
(v) Modern Pharmacology
That the earliest compilation of drugs and illness appears in “Ayurveda” claimed to have been written around 3000 B.C. Other oldest record is Pentsao seems to be have written around 2700B.C. Pentsao contained classifications or individual medicinal plants as well as compilations of plant mixtures to be used for medical purposes.
1. Egyptian Period:
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The earlier source of western medicine came from Egypt, Assyria and Babylon, “Kahun Papyrus” the oldest Egyptian drug document appears to have been written around 2000 B.C. Eber papyrus (1550 BC) is a compilation of a number of disease conditions and 829 prescriptions for medicament employed in Egyptian Medicine.
2. Greek Period:
a. Hippocreates (460-375 BC):
He is considered as the father of modern medicine. He was the first who recognized disease as an abnormal reaction of the body and not due to visitation of evil spirit. He out right rejected the primitive doctrine that wrong gods, spirits, witches etc. inflicted sufferings on human beings and their cure based on prayer and sacrifices of animals and birds, he tried to give a rational approach towards treatment of diseases.
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According to him the four elements (factors) of nature e.g. water, air, fire and earth gave rise to the four humours. Blood (Sanguine), Phlegm (Phlegmatic) yellow bile or urine (Billious), black bile (Melancholie) of the body.
Any imbalance in one or more than one humor(s) inflicted sufferings, the humoural theory of Hippocrates was very close to the contemporary prevalent Indian Philosophy that five factors like-water, fire, air, earth and space in certain proportions made the body and any imbalance in one or more than one of it lead to sufferings.
The humoural cell of Hippocrates also appear very close to the Indian Doctrine of “Tridosh” Kapha (Phlegm) Pitta (Billious) and Vayu (sanguine).
b. Aristotle (384-322 B.C.):
The scientific basis of therapy actually started with Aristotle who recorded many observations on animals. Later (Dioscorides (54-68 A.D.) a surgeon, who compiled first materia medica incorporating the works of Theophrastus (380-287 B.A.). It contained information on 600 plants.
c. Caudius Galen (131-201 A.D.):
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He dealt physiology and Materia Medica. Since the time of Hippocrates till the beginning of the period of modern medicine the treatment consisted of combination of number of plants and or earth preparations into one which was later termed as Galenical preparations.
Many of the preparations were highly obnoxious also. Galen was greatest physician after Hippocrates. His doctrines and dogma remained unchallenged up to the 15th century and his name still survives in the word “Galenicals” Pharmaceutical practice.
3. Medieval Period:
Religion dominated the world both politically and intellectually from the time of Galen to Renaissance. This is a period of degeneration. At that time Akbar was ruling the India. A change in the attitude occurred in the 16th Century.
4. Renaissance:
Printing work was done in this period. The first pharmacopeia, Valerius cordeus (1514-44) was compiled. The most influential person of that time was Theophrastus bombastus von hohenheim (1493-1541) was a Swiss physician who called him Paracelsus.
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He introduced the clinical use of Laudanum (opium) and a number of tinctures of various plants. He advocated the rational use of drugs. He insisted that drugs should be subjected to critical investigation.
a. 17th and 18th Century:
Comprised an Era of naturalism and medical experiments began. Cinchona (quinine), coffee, tea, cocoa, curare, digitalis and a variety of plant, alkaloids were used.
b. William Withering (1741-99):
He used digitalis in heart diseases-Dropsy (ascites due to congestive heart failure).
c. Edward Jenner (1749-1823):
Introduced prophylactic immunization against small pox. He was first to describe anaphylaxis (ADR). Thus, he set a stage of preventive medicine and immunization therapy.
d. William Harvey:
Discovered the circulation of blood. Before this it was not studied.
e. Cristopher Wren (1632-1723):
He was an English Architect. Made the first i.v. injection into a dog. But it was until 1853 that the hypodermic needle and syringe were device by Alexander Wood (1817-84).
f. 19th Century:
Marked development in the field of chemistry.
(a) Francois Magendie (1753-1855):
Conducted organized experiments to elucidate physiologic process and action of drug in the body.
(b) Claude Bernard (1813-78) and James and Blake (1814-93):
Drug Response Relationship; Drug disposition, mode of action of drugs.
5. Modern Pharmacology:
Started with Oswald Schmiedeberg (1838-1921). He was excellent teacher of Pharmacology and attracted many persons to study this subject. Like other experimental sciences, Pharmacology, too, is highly dependent upon development in other branches of science.
Spectacular developments in physiology, biochemistry, organic chemistry and molecular biology have greatly contributed in advancement of pharmacology. Conversion of the old pharmacology into modern pharmacology is fairly recent and probably started taking shape following introduction of experimental procedures in animals by Francois Megendie (1783-1855) and Claude Bernard (1813-1978).
Oswald Schmiedeberg (1838-1921) introduced the technique of per-fusing isolated organs and study the effects of drugs on them. Abel, Cushny, Gottlieb and a galaxy of his other students popularized the expertise in their respective, countries. Thus Oswald become popular as ‘Father of modern Pharmacology’.
John J. Abel (1857-1938):
Regarded as father of Pharmacology in USA and started Journal of Biological Chemistry and J. of Exptl. Pharma. & Therap. Following this a number of scientists like Otto Loewi (1873- 1921), Henery Hallet Dale (1954), Alexander Fleming (1881-1955), G.T.P. Domagk (1895-1964), UIF Svante Van Euler (1935) and J.R. Vane (1971) Contributed splendidly to the science of pharmacology and achieved the dignity of Nobel Laureates.
Essay on the Branches of Pharmacology:
Pharmacology can be classified into the following branches:
A. Pharmacognosy:
It is a science of identification of drugs of vegetable and animal origin. The study includes characteristics of various species of plants, their gross and cellular structures and such characteristics which serve to identify them including biosynthesis.
B. Pharmacy:
It is an art and science concerned with selection, preparation, standardisation, preservation and dispensing of medicinal substances. Dispensing of medicines may be in the form of tablets, syrup, sterile solutions for injection etc.
C. Pharmacodynamics:
It includes quantitative study of biochemical and physiological effects of drugs in therapeutic doses and their mechanism of action with respect to the chemical structure of the drug in question. In plain words it is the science which deals with as to what the drug does to the body.
Very recently a few new terms seem to be emerging from the parent term Pharmacodynamics and they are:
(a) Pharmacogenetics:
Which deals with individual variability in response to drugs. Certain genetic factors have been claimed to be responsible for such variability.
(b) Pharmacometrics:
Which deals with qualitative and quantitative evaluation of drug activity in laboratories.
D. Pharmacokinetics:
It describes the study of absorption, distribution, metabolism and excretion of drugs, and their relationship to pharmacological response. In short, it can be said that this branch of pharmacology deals with as to what the body does to the drug.
E. Therapeutics:
It is an art of medicine and is defined as any measure taken for the treatment of disease including nursing, physiotherapy and yoga.
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F. Chemotherapy:
It is concerned with the use of certain chemicals in the treatment of infectious diseases. The chemotherapeutic agents selectively act on microorganisms, parasites living and multiplying in the body. Substances employed in chemotherapy are referred to as chemotherapeutic agents.
G. Toxicology:
It is the science of poisons, and incorporates detection evaluation and their treatment. Poisons are substances that exhibit harmful/adverse and or fatal symptoms in animals or human beings. Some drugs in large doses may act as poison.
Pharmacological Records:
(i) Materia Medica:
It is older term for the science which is known as pharmacology, today. This term is now obsolete. Years ago it had a prominent place in life science and contained descriptive knowledge about drugs.
(ii) Pharmacopoeia:
It is an official-code containing list of selected established drugs and medicinal preparations with description of their physical properties and test of their identity, purity and potency. Pharmacopoeia defines the standards which these preparations must meet, and their average doses for adult.
Examples of pharmacopoeia are Indian Pharmacopoeia (I.P.), British Pharmacopoeia (B.P.) United States Pharmacopoeia (USP), British Pharmaceutical Codex (BPC), British Veterinary Codex (B.Vet.C).
(iii) National Formulatory:
It is separate official compedium of drugs and medicinal plants published by the American Pharmaceutical Association. Pharmacists often take help of this to standardize-many drugs that were not used popularly to be included in the USP. During 1978-80 it was combined with USP and the combined publication is now known as USP-NF.
From 1980-85 a representative of Veterinary Medicine has been included in the general revision committee of the USP-NF.
Similarly, British National Formulatory (BNF) is published by British Medical Association and the Pharmaceutical society of Great Britain.
The National Formulatory (NF) of India is published by the Government of India. The Formulatories contain information on products available to the prescribers in their respective countries. United States Dispensatory- It is a non-official publication from USA and contains general information on both old and new drugs found all over the world.
American Medical Association Drug Evaluation (AMA-DE)-This is a publication of the AMA council on drugs. Its main goal is to provide the physicians and other health care professionals with up-to-date unbiased information on the clinical use of drugs. It is intended to serve as a reference source for practical, comparative, evaluative information on drug therapy.
