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Introduction to pharmacology (For Allied health students)

The document provides an introduction to pharmacology, including its definitions, subdivisions (pharmacodynamics and pharmacokinetics), and the historical development of the field. It outlines the sources of drugs, including plant, animal, and synthetic origins, as well as various routes of drug administration such as oral and parenteral methods. Additionally, the text discusses principles of drug action, focusing on interactions with biological targets like enzymes, receptors, and transporters.

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Introduction to pharmacology, Routs of drug administration, Principles of drug action Dr. S. Parasuraman, M.Pharm., Ph.D., Senior Associate Professor, Faculty of Pharmacy, AIMST University, Malaysia. Introduction to Pharmacology - for allied health sciences
Introduction • Pharmacology is the science of drugs (Greek: Pharmacon—drug; logos—discourse in) • Pharmacology deals with interaction of exogenously administered chemical molecules with living systems, or any single chemical substance which can produce a biological response is a ‘drug’. • The two main divisions of pharmacology are pharmacodynamics and pharmacokinetics. • Pharmacology as an experimental science was ushered by Rudolf Buchheim who founded the first institute of pharmacology in 1847 in Germany.
Glossary • Pharmacodynamics: (Greek: dynamis-power) - What the drug does to the body. Pharmacodynamics is the study of the relationship between the concentration of drug at the site of action and the biochemical and physiological effect. • Pharmacokinetics: (Greek: Kinesis-movement) - What the body does to the drug. Pharmacokinetics is the study of drug absorption, distribution, metabolism, and excretion • Drug (French: Drogue—a dry herb): It is the single active chemical entity present in a medicine that is used for diagnosis, prevention, treatment/cure of a disease.
Glossary • Pharmacotherapeutics: Is also known as pharmacological therapy or drug therapy. It is the application of pharmacological information together with knowledge of the disease for its prevention, mitigation or cure. • Clinical pharmacology: It is the scientific study of drugs (both old and new) in man. It includes pharmacodynamic and pharmacokinetic investigation in healthy volunteers as well as in patients. • Chemotherapy: It is the treatment of systemic infection/malignancy with specific drugs.
Glossary • Pharmacy: It is the art and science of compounding and dispensing drugs or preparing suitable dosage forms for administration of drugs to man or animals. • Toxicology: It is the study of poisonous effect of drugs and other chemicals (household, environmental pollutant, industrial, agricultural, homicidal) with emphasis on detection, prevention and treatment of poisonings. • Receptor: Is a macromolecule in the membrane or inside the cell that specifically (chemically) bind a ligand (drug).
Introduction • Pharmacology in 18th Century In 1805 Friedrich Serturner, purified morphine from opium plant In 1858, Virchow proposed cell theory In 1868, first use of structural formula to describe a chemical compound In 1878, Bacteria as a cause of disease were discovered by Pasteur. (septicaemia (1878); TB (1882); cholera (1883)
Introduction • In 19th century, Oswald Schmiedeberg, regarded as the ‘father of pharmacology’. • Professor of pharmacology at the University of Strasbourg, France • In 1869 he demonstrated that muscarine had a similar effect on the heart as electrical stimulation of the vagus nerve. • He also demonstrated the hypnotic properties of urethane. • He published over 200 scientific books and articles.
Introduction • Pharmacology-become a science in 19th century • Long before that-herbal medicine was used - written pharmacopoeias • MATERIA MEDICA the science of drug preparation and the medical uses of drugs—began to develop as the precursor to pharmacology Page from the 6th century Vienna Dioscurides, an illuminated version of the 1st century De Materia Medica
Introduction • Robert Boyle, regarded as the ‘first modern chemist’, and one of the founders of modern chemistry. Robert Boyle – ‘The Sceptical Chymist’ – ‘The alchemist’ • He is best known for Boyle's law. • As a founder of the Royal Society, he was elected a Fellow of the Royal Society (FRS) in 1663
Sources of drugs
Sources of drugs • Primitive Medicine: Folklore, witchcraft, dreams, trances etc. Also from observing the reaction of some animals to particular herbs. E.g.: quinine, vitamin C was discovered. Cinchona calisaya Phyllanthus emblica Cinchona bark The barks of cinchona yield quinine used for the treatment of malaria
Sources of drugs • Plants: Plant parts such as leaves, bark, roots, flowers, seeds were used as sources for drugs. E.g.: reserpine, digitalis, morphine. Roots of Rauwolfia serpentina Reserpine is an indole alkaloid, antipsychotic, and antihypertensive drug Digitalis purpurea Digoxin used as cardiotonic agent Papaver somniferum capsule exuding latex Morphine used as analgesic
Sources of drugs • Animal sources: Obtained from animals' sources such as hormones (replacement in times of deficiencies). E.g.: Insulin from the pancreases of pigs and cattle. • Human sources: Drugs Source HCG Menotrophin Insulin Urokinase Pregnant woman Post menopausal women urine Human Human kidney cell
Sources of drugs • Microbial sources: Obtained from microbial sources such antimicrobials (AMBs). Drug Microorganisms Penicillin Chloramphenicol Griseofluvin Streptomycin Neomycin Penicilium notatum Streptomyces venezuelace Pencillin grisofullivum Streptomyces griseus Streptomyces fradiae
Sources of drugs • Minerals: E.g.: Acids, bases and salts like potassium chloride. • Synthesis of Substances: from natural products in the laboratory. • Synthetic drugs: These are chemical compounds produced in a laboratory. They can be produced commercially by drug manufacturers for valid medical purposes and are diverted from legal channels or produced illegally in clandestine laboratories for illicit markets worldwide. E.g.: Sulfonamide
Drug • The WHO (1966) has given a more comprehensive definition— “Drug is any substance or product that is used or is intended to be used to modify or explore physiological systems or pathological states for the benefit of the recipient.”
Routs of drug administration
Routs of drug administration • Most drugs can be administered by a variety of routes. • The choice of appropriate route in a given situation depends both on drug (for example, water or lipid solubility, ionization), therapeutic objectives (for example, the desirability of a rapid onset, the need for long-term treatment, or restriction of delivery to a local site) as well as patient related factors. • Major routes of drug administration include enteral, parenteral, and topical, among others.
Routs of drug administration For local action Topical Deeper tissues Arterial supply For systemic action Oral (Enteral) Sublingual or buccal (Enteral) Cutaneous Inhalation Nasal Parenteral Subcutaneous (s.c.) Intramuscular (i.m.) Intravenous (i.v.) Intradermal injection
Routs of drug administration - Oral • Oral ingestion is the oldest and commonest mode of drug administration. • Oral drugs are easily self-administered, and toxicities and/or overdose of oral drugs may be overcome with antidotes, such as activated charcoal. • Limitations of oral route of administration – Action of drugs is slower and thus not suitable for emergencies. – Unpalatable drugs are difficult to administer. – May cause nausea and vomiting. – Cannot be used for uncooperative/unconscious patient. – Absorption of drugs may be variable.
Routs of drug administration - Inhalation • Volatile liquids and gases are given by inhalation for systemic action, e.g. general anaesthetics. • Absorption takes place from the vast surface of alveoli - action is very rapid.
Routs of drug administration - Parenteral • The parenteral route introduces drugs directly into the systemic circulation. • Parenteral administration is used for drugs that are poorly absorbed from the GI tract (for example, heparin) or unstable in the GI tract (for example, insulin). • parenteral routes have the highest bioavailability and are not subject to first-pass metabolism.
Routs of drug administration - Parenteral • Parenteral – Subcutaneous (s.c.): Only small volumes can be injected s.c. Self-injection is possible because deep penetration is not needed. This route should be avoided in shock patients. – Intramuscular (i.m.): The drug is injected in one of the large skeletal muscles—deltoid, triceps, gluteus maximus, rectus femoris, etc. – Intravenous (i.v.): The drug is injected as a bolus or infused slowly over hours in one of the superficial veins. The drug reaches directly into the blood stream and effects are produced immediately (great value in emergency) (bioavailability is 100%). – Intradermal injection: The drug is injected into the skin raising a bleb (e.g. BCG vaccine, sensitivity testing). This route is employed for specific purposes only.
Principles of drug action
Principles of drug action • Drugs (except those gene based) do not impart new functions to any system, organ or cell and only alter the pace of ongoing activity. • The basic types of drug action is broadly classed as: – Stimulation – Depression – Irritation – Replacement – Cytotoxic action
Principles of drug action • Majority of drugs produce their effects by interacting with a discrete target biomolecule, which usually is a protein. • Such mechanism confers selectivity of action to the drug. Functional proteins that are targets of drug action can be grouped into four major categories, viz. enzymes, ion channels, transporters and receptors
Principles of drug action • Enzymes • Almost all biological reactions are carried out under catalytic influence of enzymes. Hence, enzymes are a very important target of drug action. – Enzyme induction – Enzyme inhibition • Competitive – Equilibrium type – Nonequilibrium type • Noncompetitive
Principles of drug action • Ion channels • Proteins which act as ion selective channels participate in transmembrane signaling and regulate intracellular ionic composition.
Principles of drug action • Transporters • Several substrates are translocated across membranes by binding to specific transporters (carriers) which either facilitate diffusion in the direction of the concentration gradient or pump the metabolite/ion against the concentration gradient using metabolic energy. – ligand gated channels – G-protein regulated channels
Principles of drug action • Receptors • It is defined as a macromolecule or binding site located on the surface or inside the effector cell that serves to recognize the signal molecule/drug and initiate the response to it, but itself has no other function. • Drug-receptor interaction – Agonist – Inverse agonist – Antagonist – Partial agonist – Ligand
Principles of drug action • Receptors • Drug-receptor interaction – Agonist: An agent which activates a receptor to produce an effect similar to that of the physiological signal molecule. – Inverse agonist: An agent which activates a receptor to produce an effect in the opposite direction to that of the agonist. – Antagonist: An agent which prevents the action of an agonist on a receptor or the subsequent response, but does not have any effect of its own. – Partial agonist: An agent which activates a receptor to produce submaximal effect but antagonizes the action of a full agonist. – Ligand: Any molecule which attaches selectively to particular receptors or sites.
Introduction to pharmacology (For Allied health students)