Pharmacology is the science that deals with the study of drugs and their interaction with the living systems. The word pharmacology is derived from Greek—‘Pharmacon’ means drug and ‘logos’ means study.
Man knew the useful and toxic effects of many plant and animal products even in ancient times.
In early days there was a close relationship between religion and treatment of diseases. The knowledge of the use of drugs often rested with the priest or holyman. Drugs were thought to be magical in their actions. Though medicine developed simultaneously in several countries, the spread of knowledge was limited because of poorly developed communication across the world.
Several cultures like the Chinese, Greek, Indian, Roman, Persian, European and many others contributed a great deal to the development of medicine in early times. The drug prescriptions included preparations from herbs, plants, animals and minerals. In the middle ages, many herbal gardens were cultivated particularly by the monasteries.
The earliest writings on drugs are the Egyptian Medical Papyrus (1600 BC). The largest of them, Ebers Papyrus (1550 BC) lists some 800 preparations.
India's earliest pharmacological writings are from the ‘Vedas’. An ancient Indian Physician Charaka and then Sushruta and Vagbhata described many herbal preparations included in ‘Ayurveda’ (meaning the science of life). Indians practiced vaccination as early as 550 BC.
Various other traditional systems of medicine were practiced in different parts of the world—like Homeopathy, Unani, Siddha system and Allopathy.
Allopathy means ‘the other suffering’. This word still being used for the modern system of medicine, is not correct (a misnomer). Homoeopathy meaning ‘similar suffering’ was introduced by Hannemann. The principles of this system are ‘like cures like’ and ‘dilution increases the potency of drugs’.
Thus several systems of medicine were tried but only a few survived. The basic reason for the failure of many systems is that man's knowledge of diseases were incorrect and baseless in those days. By the end of the 17th century the importance of experimentation and observation and scientific methods of study became clear. Francois Magendie and Claude Bernard popularized the use of animal experiments to understand the effects of drugs. Simultaneous development of other branches of science like botany, zoology, chemistry and physiology helped in the better understanding of pharmacology.
The last century has seen a rapid growth of the subject with several new drugs, new concepts and techniques being introduced. We now know much more about receptors and molecular mechanisms of action of many drugs. Several diseases which were considered incurable and fatal can now be completely cured with just a few tablets.
Drug (Drogue means a dry herb in French) is a substance used in the diagnosis, prevention or treatment of a disease. WHO definition, “A Drug is any substance or product that is used or intended to be used to modify or explore physiological systems or pathological states for the benefit of the recipient.”
Pharmacokinetics is the study of the absorption, distribution, metabolism and excretion of drugs, i.e. what the body does to the drug (in greek Kinesis = movement).
Pharmacodynamics is the study of the effects of the drugs on the body and their mechanisms of action, i.e. what the drug does to the body.
Therapeutics deals with the use of drugs in the prevention and treatment of disease.
Toxicology deals with the adverse effects of drugs and also the study of poisons, i.e detection, prevention and treatment of poisonings. (Toxicon = poison in Greek).
Chemotherapy is the use of chemicals for the treatment of infections. The term now also includes the use of chemical compounds to treat malignancies.
Pharmacy is the science of identification, com-pounding and dispensing of drugs. It also includes collection, isolation, purification, synthesis and standardization of medicinal substances.
SOURCES OF DRUGS
The sources of drugs could be natural or synthetic.
Natural sources: Drugs can be obtained from:
- Plants, e.g. atropine, morphine, quinine, digoxin, pilocarpine, physostigmine.
- Animals, e.g. insulin, heparin, gonadotrophins and antitoxic sera.
- Minerals, e.g. magnesium sulphate, aluminium hydroxide, iron, sulphur and radioactive isotopes.
- Microorganisms: Antibacterial agents are obtained from some bacteria and fungi. We thus have penicillins, cephalosporins, tetracyclines and other antibiotics.
- Human: Some drugs are obtained from man, e.g. immunoglobulins from blood, growth hormone from anterior pituitary and chorionic gonadotrophins from the urine of pregnant women.
Synthetic: Most drugs are now synthesized, e.g. quinolones, omeprazole, sulfonamides, pancuro- nium, neostigmine.
Many drugs are obtained by cell cultures, e.g. urokinase from cultured human kidney cells. Some are now produced by recombinant DNA technology, e.g. human insulin, tissue plasminogen activator and some drugs by Hybridoma Technique, e.g. monoclonal antibodies.
DRUG INFORMATION SOURCES
Books that are sources of information on drugs, i.e. Pharmacopeias and formularies are together known as Drug Compendia. Drug compendia are of two types.
- Official compendia
- Drug formulary
- Non-official compendia
1. Official Compendia
Official compendia include information sources (or books) on drugs which are recognized by the government of that country as ‘legal standard’. Thus, Indian Pharmacopeia, National formulary, British Pharmacopeia, British Pharmaceutical codex, United States Pharmacopeia and such other Pharmacopoeias are official compendia.
Pharmacopeia: Pharmacopoeia is the official publication containing a list of drugs and medicinal preparations. In Greek ‘Pharmacon’ means drug and ‘poeia’ is to make. It contains a list of drugs and related substances that are approved for use, their source, formulae and other information needed to prepare the drugs, their physical properties, tests for their identity, purity and potency. Each country may follow its own pharmacopeia. We thus have Indian Pharmacopeia, British Pharmacopeia, United States Pharmacopeia, USSR and Japanese Pharmacopeia. The European Pharmacopeia was published by the Public Health Committee and the European Pharmacopeia commission. The International Pharmacopeia is published by WHO in many languages like English, French, Spanish and Russian.
The first pharmacopeia of India was published in 1868. But later under the British rule, the British Pharmacopeia was followed. After independence, a committee was set up and Indian Pharmacopeia was released in 1955. Experts from pharmaceutical industry, drug control laboratories and research and teaching institutions helped the committee.
All pharmacopeias are revised at regular periods to delete old useless drugs and to include newly introduced ones.
Drug formulary also provides information on drugs. The National formulary is a smaller book that contains information on formulations which are used therapeutically. It is prepared by the National formulary committee set up by the ministry of health, Government of India. Expert opinion is also taken from medical associations, hospitals, teaching institutions and pharmaceutical industry in preparing this book.
2. Non-official Compendia
The books other than the official compendia which provide information on drugs are known as non-official drug compendia. These include the textbooks of pharmacology, journals and periodicals.
Textbooks like—the pharmacological basis of therapeutics by Goodman and Gilman, Merck Index, The United States Dispensary, Remington's Pharmaceutical Sciences and others are quite informative. Many Indian textbooks are also available.
Several journals are published by local, national and international medical organizations. They provide updated information on drugs with research and review articles.
Local: Several regional (e.g. Sourthern, northern) and state level medical societies release journals at regular intervals.
National: Indian pharmacological society, Indian society of clinical pharmacology and other similar national level organizations bring out journals at regular intervals.
Some National Journals
- Indian Journal of Pharmacology
- Indian Journal of Physiology and Pharmacology
- Indian journal of Clinical Pharmacology
- Journal of Association of Physicians of India
- Indian Journal of Hospital Pharmacy.
International: WHO and other international associations publish journals.
Some International Journals
- Advanced Drug Delivery Reviews
- Anti-Cancer Drugs
- Clinical Pharmacology and Therapeutics
- Drug Resistance updates
- International Clinical Psychopharmacology
- International Journal of Antimicrobial Agents
- International Journal of Drug Policy
- The Lancet
Periodicals are published at regular intervals like monthly or annually. Some of them are:
Indian Drug Review: It is a private publication released every 2 months.
Monthly Index of Medical Specialties (MIMS, India): It is published every month. It is an independent professionally edited list of preparations available in India. It is updated every month. When full product information is required, it may be obtained from the editor of MIMS.
Current Index of Medical Specialties (CIMS): It is published every three months. It contains information on the list of drugs and medicinal preparations from different manufacturers and the information is updated every three months.
With the advancement of technology, we now have e-sources of information like the medline. Several books also provide soft copies or CDs for use on the computer.
Medline or medical literature analysis and retrieval system online is a literature data base of life sciences and biomedical information. Medline includes literature in medicine, nursing, pharmacy, dentistry, health care and veternery medicine. It also includes literature in biology including molecular biology. Medline is compiled by the National library of medicine USA. It is freely available on the internet and can be searched via Pubmed.
The Medline contains database with more than 17 million records from 1950 onwards. For indexing, Medline uses medical subject headings (MeSH) to retrieve engines like Entrez to search medline. Medline includes about 5000 leading biomedical journals. There are thousands of references in the journals database.