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Introduction to General Pharmacology

 

 Pharmacology is the science that deals with drugs. Pharmakon (an active principle) and Logos (a disease or treatment) = (Greek)

       History of drug is as old as disease. World’s oldest known pharmacological writings come from India (Vedas) and China (Pan Tsao). Medical description in Rigveda (3000 BC) – Charaka, later Sushruta and Vagbhata, who described various medicinal preparations included in Ayurveda (the science of life). Mostly contain non-poisonous herbal drugs and minerals. Charaka classified 300 herbal drugs according to their effects, mostly on symptoms into 50 groups.

       ‘Pan Tsao’ (2735 BC) contained many plants and metallic preparations and a few animal products. Earliest source of Western Medicine comes from Egypt and two kingdoms of Assyria and Babylonia. ‘Papyri’ is the first written account of medical experience from Egypt (1900 BC) – mentions about 700 herbal remedies including opium. Babylonian clay tablet (700 BC) mentions about 300 drugs.

       Modern medicine dates from Hippocrates (Greek – 450 BC) – the concept of disease as a pathologic process and organized the science of medicine on the basis of observation, analysis and deduction. He recommended judicious use of simple and efficacious drugs.

       Till beginning of 19th century, treatment included such obnoxious remedies as flesh, excreta, blood of various animals along with a few metal and plant preparations. James Gregory (1753 – 1821) popularized heroic symptomatic treatment consisting of blood letting, large doses of emetics, drastic purgatives. Such treatment without any rational basis was called “Allopathy” (meaning the other suffering). Homeopathy (meaning similar suffering) by Hannemann in early 19th century, who thought, “Like cures like” and “dilution potentiates the action of drugs”.

       Development of modern pharmacology is fairly recent and started taking shape following experimental procedures in animals by Francois Magendie (1783 – 1855) and Claude Bernard (1813 – 1878). Till then, treatment of diseases was empirical, based on combination of guess work and experience. Spectacular developments in physiology, bio-chemistry, organic chemistry and molecular biology greatly accelerated the advances in pharmacology.

        With increasing knowledge about the patho-physiology of diseases, their drug therapy has now become more rational. The object of pharmacology is mainly to provide such scientific data, using which one can choose a drug treatment of proven efficacy and safety from the various options available, to suit the patient.

       The word ‘Drug’ is derived from the French word ‘Drogue’, a dry herb. A drug is defined as “any substance used for the purpose of diagnosis, prevention, relief or cure of a disease in man or animals.”

       However, WHO defines it, “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.”

       Pharmacology: Consists of detailed study of drugs, particularly their effects on living animals, organs or tissues. Actions may be beneficial or harmful. It includes:

1)    Pharmacognosy: Science of identification of drugs.

2)    Pharmacy: Science of identification, selection, preservation, standardization, compounding and dispensing of medicinal substances.

3)    Pharmacokinetics:  Study of absorption, distribution, metabolism and excretion of drugs (what body does to the drugs)

4)    Pharmacodynamics:  Quantitative study of biological and therapeutic effects of drugs (what drug does to the body)

Dosage Regimen>> Pharmacokinetics>> Concentration in Plasma>> Concentration at the site>> Pharmacodynamic effects.

5)    Therapeutics: (To cure for, to tend to or to nurse), a branch of medicine concerned with the cure of disease or relief of symptoms; it includes drug treatment.

6)    Toxicology:  Science of poisons. It includes detection and measurement of poison as well as treatment of poisoning. Poisons are those that cause harmful, dangerous or fatal symptoms in humans and animals. Many drugs in larger doses act as poisons.

7)    Chemotherapy:  Effect of drugs upon microorganisms and parasites, living and multiplying in a living organism.

8)    Pharmacoepidemiology:  Study of the use and effects of drugs in large number of peoples.

9)    Pharmacogenetics: Study of inherited (genetically mediated) differences (variation) in drug metabolism and response in humans.

10) Pharmacovigillance:  Process of identifying and responding to the issues of drug safety through the detection of drug effects, usually adverse. It is related to the surveillance of drugs once they are released for use in the community and relies on voluntary reporting, prescription monitoring, medical records and statistical studies in the population.

11) Clinical Pharmacology:  Involves cooperation of the pharmacist with the physicians in educating the patient about compliance and counseling him on how to take the medication, and monitoring the errors in taking the drugs.

12) Pharmacopoeia:  (like, IP, USP) - An official code containing selected list of the established drugs and medicinal preparations with description of their physical properties and tests for their identity, purity and potency. It defines the standards which these preparations must meet and may mention their average doses for an adult.

13) Formulary: (like, National Formulary, British National Formulary) - It includes information on products available to prescribers in the respective countries.

14) Codex: (like British Pharmaceutical Codex, B.P.C) - It gives information on drugs, other pharmaceutical substances and formulated products. Further, it provides standards for identification and purity for a range of substances and materials for which standards are not provided by the British Pharmacopoeia (B.P).

15) Extra-pharmacopoeia (Martindale, The Complete Drug Reference) – A voluminous database, published periodically. Aims to provide unbiased concise reports on the actions and uses of most of the World’s drugs and medicines to aid the practicing Pharmacists and physicians. It also contains, “references, reviews of important and contentious topics to back up editorial text and has a wide coverage of proprietary names.”

 

Tapas Kumar Bhattacharyya 06.11.2017 0 1066
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06.11.2017 (408 days ago)
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