Basic Pharmacology-I Lecture Notes PDF

Basic concepts and principles of Pharmacology-I Jan 1 2025 What is pharmacology? Pharmacology is the science that deals with the detailed study of drugs, particularly their actions on living animals, organs and tissues. The actions may be beneficial or harmful  What is...

Basic concepts and principles of Pharmacology-I Jan 1 2025 What is pharmacology? Pharmacology is the science that deals with the detailed study of drugs, particularly their actions on living animals, organs and tissues. The actions may be beneficial or harmful  What is a Drug? Any substance intended for use in diagnosis, prophylaxis, mitigation, treatment or cure of diseases in humans or animals, and such substances intended to affect the functioning of any structure found in human and animal body  The word pharmacology is derived from the Greek words pharmakon (drug) and logos (study). The word drug has also a French origin-- 'drouge' (dry herb). In clinical practice, drug is a chemical substance that is used for the diagnosis, prevention and treatment of diseases in appropriate doses. WHO (1966) definition of a drug is any substance or product that is used or intended to be used to modify or to explore physiological system or pathological states for the benefit of the recipient  Subdivisions of pharmacology Pharmacy is a branch of pharmacology that deals with identification, selection, preservation, combining, analyzing, standardization, preparing, compounding and dispensing of medicines for administration to the patient. A pharmacist prepares compounds and dispenses medicines to the patient upon a written order of a licensed medical practitioner  Pharmacognosy is a term derived from the Greek word 'gnosis' which means knowledge. It is a branch of pharmacology that deals with the sources of drugs derived from plants and animals The branch of knowledge concerned with medicinal drugs obtained from plants or other natural sources  Pharmacokinetics is a term derived from the Greek word 'kinesis' meaning a movement. It deals with the time course of drug absorption, distribution, metabolism and excretion. In other words, it means "What the body does to the drug" Pharmacodynamics (Greek 'dynamics' means force) is the study of physiological and biochemical effects of drugs, mechanisms of action and the relationship of the plasma concentration of the drug with its response and the duration of action. In other words, it means "What the drug does to the body"  Pharmacotherapeutics (Greek 'therapia' means medical treatment) deals with the use of drugs in the diagnosis, treatment or prevention of a disease or their purposeful use in alteration of physiological functions for the benefit of the recipient Therapeutics deals with the science and art of treatment of diseases. When therapy is based on clinical evidence it is called Empirical Therapeutics  Chemotherapy deals with the use of chemotherapeutic agents to inhibit or destroy invading microbes, parasites or cancer cells with minimal effect on healthy living tissues Toxicology (Greek 'toxicon' means poison) is the science of poisons. It deals with the adverse effects of drugs and poisonous effects of various chemicals (household, environmental, industrial or homicidal). It is also concerned with their source, chemical composition, action, tests for detection and antidotes  Pharmacogenetics is a relatively new field. It deals with genetically mediated variations in drug responses Clinical Pharmacology is a branch of pharmacology that deals with the pharmacological effects of drugs in man  Biopharmaceutics deals with the development of new drug delivery systems and new dosage forms. It also provides information how these dosage forms can influence the pharmacodynamic and pharmacokinetic properties of a drug Medicinal Chemistry is the science of designing and synthesis of a new drug. It is based on the structure activity relationship data of existing drugs belonging to one generic group  Sources of drugs I. SYNTHETIC SOURCES: At present majority of drugs used in clinical practice are prepared synthetically, such as aspirin, oral antidiabetics, antihistamines, amphetamine, chloroquine, chlorpromazine, general and local anaesthetics, paracetamol, phenytoin, synthetic corticosteroids, sulphonamides and thiazide diuretics Advantages of synthetic drugs are: They are chemically pure The process of preparing them is easier and cheaper. Control on the quality of the drug is excellent. Since the pharmacological activity of a drug depends on its chemical structure and physical properties, more effective and safer drugs can be prepared by modifying the chemical structure of the prototype drug II. NATURAL SOURCES Drugs are obtained from the following natural sources: A- PLANTS: Following categories of drugs are derived from roots, leaves or barks of plants: a) Alkaloids These are nitrogenous heterocyclic bases, which are pharmacologically active principles of plants. They are composed of carbon, hydrogen, nitrogen and oxygen. They are bitter in taste and are often poisonous. These are, therefore, used in small doses. They are insoluble in water. However, they form salts with acids which are soluble in water Some examples of alkaloids and their sources are listed in the table: ALKALOID SOURCE Atropine Atropa belladonna Quinine Cinchona bark Morphine Papavarum somniferum Reserpine Rauwolfia serpentina Nicotine Tobacco Digoxin Digitalis lanata Caffeine Coffee, Tea, Cocoa  b) Glycosides They are ether-like combination of sugar moiety with non-sugar moiety. They are called glucosides, if the sugar moiety is glucose. Sugar moiety is not essential for the pharmacological activity but it governs the pharmacokinetic properties of the glycoside. In the body it may be removed to liberate aglycone. Pharmacological activity resides in the non-sugar moiety that is called aglycone (or genin). Examples are digitoxin and digoxin c) Oils. They are liquids which are insoluble in water. They are of three types and are used for various medicinal purposes. i) Essential Oils (or volatile oils): Essential oils are obtained from leaves or flower petals by steam distillation, and have an aroma  They have no caloric or food value. They do not form soaps with alkalies. They do not leave greasy stain after evaporation. On prolonged stay, they do not become rancid (foul smell). They are frequently used as carminatives and astringents in mouth-washes. Some of these oils are solid at room temperature and sublime on heating e.g. menthol and camphor. Other examples are clove oil, peppermint oil, eucalyptus oil and ginger oil  ii)Fixed oils are glycerides of stearic, oleic and palmitic acid. They are obtained from the seeds that are present within the cells as crystals or droplets. They are non-volatile and leave greasy stains on evaporation. They have caloric or food value. They form soaps with alkalies. On prolonged stay, they become rancid. They do not have marked pharmacological activity and have little pharmacological use except castor oil (purgative) or arachis oil (demulcent) They may be of vegetable origin e.g. olive oil, castor oil, croton oil and peanut oil or of animal origin e.g. cod liver oil, shark liver oil and lard.  iii)Mineral Oils are mostly petroleum products and extracted by fractional distillation. These are mixtures of hydrocarbons of the methane and related aliphatic series. These are extracted in various consistencies - hard paraffin, soft paraffin and liquid paraffi n. Hard and soft paraffins are used as vehicles for preparation of ointments while liquid paraffi n is employed as a purgative  d)Gums are colloidal exudates from plants which are polysaccharides chemically and yield simple sugars on hydrolysis. Upon addition of water, some of them swell or dissolve or form adhesive mucilage or remain unchanged. Uses: - In gut agar and psyllium seeds act as hydrophilic colloids and function as bulk purgatives. Gum acacia and gum tragacanth are used as suspending agents in making emulsions and mixtures  e)Resins are ill-defined solid substances found in plants, and are polymers of volatile oil. They are produced by oxidation and polymerization of volatile oils. They are insoluble in water but soluble in alcohol, chloroform and ether. Examples: oleoresins (aspidium); gum resins (asafoetida); oleogum resin (myrrh); balsams (benzoin, tolu, peru); benzoin shellac, podophyllum. Uses:   Benzoin is used as inhalation in common cold.  Tincture benzoin is applied as antiseptic protective sealing over bruises.  Colophony (an oleoresin) is used as an ingredient in various plasters.  Shellac (from Lucifer lacca) is used for enteric coating of tablets.  Balsams are used in the treatment of cough and bronchitis for their antiseptic and protective properties. Podophyllum is used as an irritant purgative f) Tannins are non-nitrogenous phenolic plant constituents which have an astringent action Tannic acid is tannin that is obtained from oak galls and is used for treating burns and diarrhoea B-ANIMAL SOURCES Some animal sources continue to be used to procure some modern drugs because of cumbersome and expensive procedures for the synthesis of such chemicals. For example: Insulin, extracted from pork and beef pancreas, is used for the treatment of diabetes mellitus. Thyroid powder for treating hypothyroidism. Heparin is used as an anticoagulant. Hormones and vitamins are used as replacement therapy. Vaccines (cholera, T.B., smallpox, polio and antirabic) and sera (antidiptheria and antitetanus) are used for prophylaxis/treatment C-MICROBIOLOGICAL SOURCES Many life-saving drugs are obtained from fungi, moulds and bacteria e.g. penicillin from Penicillium notatum, chloramphenicol from Streptomyces venezuelae, griseofulvin (an anti-fungal drug) from Penicillium griseofulvum, neomycin from Streptomyces fradiae and streptomycin from Streptomyces griseus D-MINERAL SOURCES Minerals or their salts are useful pharmacotherapeutic agents. For example: Ferrous sulfate is used in iron deficiency anaemia. Magnesium sulfate is employed as purgative. Magnesium trisilicate, aluminium hydroxide and sodium bicarbonate are used as antacids for hyperacidity and peptic ulcer. Kaolin (aluminium silicate) is used as adsorbent in anti-diarrhoeal mixtures. Radioactive isotopes of iodine, phosphorus, gold III. SEMISYNTHETIC SOURCES Sometimes semi-synthetic processes are used to prepare drugs when the synthesis of drugs (complex molecules) may be diffi cult, expensive and uneconomical or when the natural sources may yield impure compounds. Some examples are semisynthetic human insulin and 6-aminopenicillanic acid derivatives IV. BIOSYNTHETIC SOURCES (genetically engineered drugs) This is relatively a new field which is being developed by mixing discoveries from molecular biology, recombinant DNA technology, DNA alteration, gene splicing, immunology and immunopharmacology. Some of the recent developments are genetically engineered novel vaccines (Recombinex HB - a hepatitis-B vaccine), recombinant DNA engineered insulins (Humulin- human insulin) for diabetes and interferon-alpha-2a and interferon-alpha-2b for hairy cell leukaemia  Drug Nomenclature: System of naming drugs Chemical Name: It describes the substance chemically and the naming is based on chemical structure of a medicinal compound. Indicates the precise arrangement of atoms and atomic groups in the molecule. However, chemical names are too complex and cumbersome to be used in prescription.  Non-Proprietary Name (Generic): It is the name accepted by a competent scientific body such as the United States Adopted Name (USAN) and is reflected in pharmacopoeia, e.g. Aspirin, Ibuprofen, Atenolol, etc. These names are used uniformly all over the world by an international agreement through the W.H.O. Non-proprietary name is called official when included in official books such as Indian, British, United States or International pharmacopoeia. The non-proprietary name is often referred to as generic name  Proprietary Name (Brand): Name assigned by the manufacturer and is his property/ trademark. One drug may have multiple proprietary names. The pharmaceutical company, which sells the non-proprietary drug selects the proprietary name and gets it registered. Proprietary name is usually smaller than the non- proprietary name and it is most widely used by medical practitioners. Some examples are:  Non-Proprietary Chemical Name Proprietary Name Name -1-(4- Diabinese chlorobenzenesulph Chlorpropamide ®Copamide ® onyl-3-propylurea) (Dey's) - chlorodihydrometh Valium ® (Roche, yl-phenyl Diazepam India) Calmpose ® benzodiazepine-2- (Ranbaxy, India) one ® is suffixed on the trade name indicating registered name  Prototype Drug Usually, attention is focused on one or at the most two drugs belonging to a group in order to comprehend and co-relate their pharmacological effects with the other drugs of the same group. Drugs selected for this purpose are called prototype drugs e.g. chlorpromazine is a prototype drug for anti- psychotic drugs and morphine is a prototypal drug for narcotic analgesics.  DRUG INFORMATION SOURCES 1.Pharmacopoeia: It is an official code containing a selected list of the established drugs and medicinal preparations with descriptions of their physical properties, identification, purity, potency and the minimum standard required and the average dose for adults Each country has its own pharmacopoeia. For example: British Pharmacopoeia United States Pharmacopoeia Indian Pharmacopoeia European Pharmacopoeia Russian Pharmacopoeia International Pharmacopoeia 2. ​Formulary: It includes information on drugs, other pharmaceutical products and formulated products in the respective countries. British National Formulary is published by the British Medical Association National Formulary is published by American Pharmaceutical Association. National Formulary of India is published by the Government of India BNF – Bhutan National Formulary Any Questions?