Nature and Nomenclature of Drugs

1. Nature and Nomenclature of Drugs

2. Nature of drugs Physical Structure • Solid (aspirin) • Liquid (nicotine, ethanol) • Gas (nitrous oxide) Chemical structure • Protein, lipid, carbohydrate • Weak acid or weak base • Amine (primary, secondary, tertiary)

3. Characteristics of an Ideal Drug? • Selective (e.g. if you give a drug for heart, it should only work on the heart) • It should have minimum adverse effects • Temporary (it does not change the function permanently) • It should be highly effective (efficacious) at low doses (potent) • Dose-related (controllable) • It should be safe in a wide range of doses (therapeutic index) • It should have convenient dosing regimens

4. How are Drug Responses Produced? • Drug actions are mediated by 3 ways: • Acting on somatic or psychic processes or functions • Correction of deficiencies • Toxic action on pathogenic microorganism

5. How are Drug Responses Produced? By interaction with active binding sites called Drug Targets (e.g. receptors, enzymes, ion channels etc.) Drug may be agonist or antagonist for the receptors

6. Drug Properties Influencing Drug Actions Drug Size • The molecular size of drugs varies from very small (lithium ion, MW 7) to very large (eg, alteplase [tPA], a protein of MW 59,050). • However, most drugs have molecular weights between 100 and 1000. • The specificity of drug action requires a drug molecule must be sufficiently unique in shape, charge, and other properties • To achieve such selectivity, a molecule should be at least 100 MW units in size. • Drugs much larger than MW 1000 do not diffuse readily between compartments of the body

7. Drug Shape • The shape of a drug molecule must be such as to permit binding to its receptor site via the bonds just described. • Optimally, the drug's shape is complementary to that of the receptor site in the same way that a key is complementary to a lock.

8. Criteria for drug classification Drugs can be classified in many ways based on • Chemical structure • Cholinesters • Organophosphates • Catecholamines • Location of action • Cardiac glycosides • Autonomic drugs

9. Criteria for drug classification • Purpose of medication • Antihypertensive • Diuretic • Antiemetic • Analgesic • Name of plant • Opium alkaloids • Cardiac glycosides • Belladonna alkaloids

10. Prescription vs Over the Counter Drugs Prescription Drugs These drugs that cannot be obtained from a pharmacy without a registered physician’s prescription. Over-the-Counter (OTC) Drugs These drugs are available without a physician’s prescription for self-treatment of a variety of complaints. Some drugs are approved as prescription drugs but later are found to be very safe and useful for patients without the need for prescription. Potential problems with OTC drugs • Taking these drugs could mask the signs and symptoms of underlying disease making diagnosis difficult • Taking these drugs with other drugs can result in drug interactions • Can result in drug overdoses

11. Sources of drugs • Natural Sources: Substances obtained directly from nature • Plants • Animals / Humans • Micro-organisms • Minerals • Inorganic metals • Semi-synthetic • Synthetic • Bio-synthetic

12. Sources of drugs Natural from Plants Active principles are found in roots, leaves and seeds in 3 forms: • Glycosides • Cardiac glycoside Digoxin ( from the Foxglove plant) • Alkaloids • Morphine (from Poppy capsules), • Atropine (from Belladonna leaves) • Quinine (from bark of Cinchona tree) • Castor oil (from castor seed)

13. Sources of drugs Natural from animals / humans • Hormones • Heparin from Pig or Ox liver, • Insulin from Pig or Ox pancreas • Gonadotrophins from urine of postmenopausalwomen • Plasma or serum from blood • Thyroxin from Pig or Ox thyroid gland • Cod Liver Oil from Cod fish Liver

14. Sources of drugs Natural from micro-organisms Antibiotics • Penicillin from Penicilliumnotatum, • Streptomycin from Streptomycesgriseus, • Bacitracin from Bacillus

15. Sources of drugs Minerals • Calcium, Magnesium, Aluminium, Sodium, Potassium & Iron salts • Liquid paraffin from petroleum. Inorganic metals • Iodine • Lithium • Radioactive elements: Iodine (I131)

16. Sources of drugs Semi synthetic drugs Prepared by chemical modification of natural drugs in labs. • Ampicillin from Penicillin-G, • Semisynthetic cephalosporin's from 7-amino cephalosporinic acid

17. Sources of drugs Synthetic Drugs Prepared by chemical synthesis in pharmaceutical laboratories • Sulphonamides • Salicylates • Barbiturates • Benzodiazepines

18. Sources of drugs Synthetic / semisynthetic Drugs • Technical advances allow scientists to alter a chemical with proven therapeutic effectiveness to make it better. • Sometimes, a small change in chemical’s structure can make that chemical more useful as a drug – more potent, more stable, less toxic. • These technological advance have led to the development of groups of similar drugs, all of which are derived from an original prototype, but each of which have slightly different properties, making a drug more desirable in a specific situation.

19. Sources of drugs Bio-Synthetic Drugs • Scientists use genetic engineering to alter bacteria to produce chemicals that are therapeutic and effective. • Prepared by cloning of human DNA into bacteria such as E. Coli.

20. Sources of drugs Bio-Synthetic Drugs Technique is called Recombinant DNA technology (or Genetic Engineering) • Cells are obtained from animals or human that produce required substance (e.g. a hormone) • Isolation of DNA or DNA fragment encoding the substance • Transfer of encoding DNA fragment to bacteria (E-coli) via plasmids (Gene cloning) • The transformed E-coli synthesizes the new substance

21. Sources of drugs Examples of Bio-Synthetic Drugs • Human Insulin • Human Growth Hormones • Human Hepatitis B Vaccine

22. Sources of Drug Information • Saudi MOH (Ministry Of Health) Drug List (see notes below) • Pharmacopoeias • “Up to date” website • Elsevier “Gold standard” Clinical Pharmacology website • Micromedex (www.micromedex.com) • Drug labels (see next slide) • Package inserts • Drug references (e.g. Physician’s drug reference) • Journals • Internet (e.g. wikipedia)

23. Drug Nomenclature Chemical name • Based on the chemical composition and structure Generic name (Official, Approved) • This is usually the abbreviated form of the chemical name • This name is used and chosen by official bodies Proprietary name (Brand name, Company name) • the name given by the company which markets the drug • It is the commercial property of a pharmaceutical company • It indicates a particularly formulation of a particular substance by a particularly manufacturer

24. Generic Drugs vs Brand Name Drugs Generic name: • When a company brings a new drug onto the market, the firm has already spent substantial money on research, development, marketing and promotion of the drug. A patent is granted that gives the company that developed the drug an exclusive right to sell the drug as long as the patent is in effect under it’s brand name e.g. generic name for metformin is “METFORMIN”(used for treating diabetes) Brand name: • Are copies of generic-name. In other words, their pharmacological effects are exactly the same as those of their generic-name counterparts e.g. for diabetes “METFORAL” or “GLUCOPHAGE” • Brand drugs are only cheaper because the manufacturers have not had the expenses of developing and marketing a new drug….but be careful about brand drugs from underdeveloped countries

25. Drug Nomenclature • Since several companies market the same drug under different proprietary names, which creates unnecessary confusion • Whenever possible drugs should be prescribed by their GENERIC names • Chemical name: Acetyl-p-aminophenol • GENERIC name:Paracetamol or (acetaminophen) • Proprietary name:Panadol, Calpol, Adol, Fevadol

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