Drugs and Medicines

1. Drugs and Medicines Version 1.05 1

2. Health and the Human Body • The human body maintains an intricate balance of thousands of chemical reactions. • These systems must respond to constantly changing demands from the individual’s activities. • These systems are subject to challenges from defects and malfunctions resulting from • genetic abnormalities. • environmental challenges. • changes accumulated through age. • attacks from microorganisms. 2

3. Lines of Defense • Barriers to prevent entry • Skin • Mucous membranes • Closures and secretions of natural openings: lips, eyelids etc. • Defense against attack invaders • White blood cells (Phagocytes)] • Blood clotting to prevent blood loss • Inflammatory response. • Immune system • Antibodies. • Memory cells to enable the body to fight repeat invasions. 3

4. Origins of Pharmacology • From earliest times people have used natural substances such as medicinal herbs to -- relieve pain -- heal injuries -- cure diseases • Some folk remedies contained certain active ingredients that were of medicinal value. 4

5. Examples of Folk Remedies • Morphine • extracted from poppy used to treat pain in the 19th century. • Salicylic acid • extracted from willow bark an a precursor to aspirin. • Quinine • Used in South America to treat malaria. 5

6. Definition of a Medicine • Any chemical substance that • Alters a physiological state • Alters mood or emotions • Alters incoming sensory sensations • Sometimes it is difficult to determine whether a drug has any medicinal value. • The legitimate purpose of a drug is usually to improve health. • Use of drugs in some cases is controversial. 6

7. The Placebo Effect • Healing is a complex interaction between mind and body that is not entirely understood. • The Placebo Effect Merely taking any medicine may trigger responses in the body that result in changes in the mental/emotional or physiological states of the person without having any medicinal action. 7

8. Drugs and Medicines • Access to drugs and medicines is controlled in most countries but the definition of what constitutes a drug may vary. • Examples: • Melatonin • Codeine 8

9. Methods of Administering Drugs • Drugs must reach blood stream to be transported to critical tissues. • The method of administration determines rate at which the drug is absorbed in the blood. • Five common points of entry: • Oral • Inhalation • Topical • Injection • Anal 9

10. Methods of Administering Drugs Injection methods • Intradermal Between layers of skin • Subcutaneous Under the skin • Intramuscular In the muscle • Intravenous Directly in the vein 10

11. Research, Development and Drug Testing • Development of new drugs is long and expensive process • Several stages in development include: • Isolation or chemical synthesis • Laboratory studies • Animal testing to determine LD50 • Clinical testing to determine effectiveness • Approval by the FDA for market 11

12. Research, Development and Drug Testing • The development of a new drug is a time consuming process • Determination of the Lethal Dose or LD50. This is the concentration that will kill 50% of the animals in a test sample • The Effective Dose or ED50. is the concentration necessary to bring about a noticeable effect in 50% of the test sample • The Therapeutic Index is the ratio of LD50. ED50. 12

13. Clinical Trials • All drugs that are approved for market must be clinically tested multiple times • Most clinical tests are done on volunteers using a double blind study • Some of the volunteers receive a placebo while others receive the therapeutic medicine • Neither the researcher nor the participants know in advance who receives which 13

14. Drug Development • All medicines have some side effects and the appropriate dosage must be determined. • To determine the following must be considered: • Lethal Dose or LD50 • Effective Dose or ED50 • Therapeutic Index • Toxic Range • Therapeutic Level • Sub-therapeutic level 14

15. Contraindications or Side Effects • Contraindications are additional and often undesirable effects that result from the use of a particular drug to treat a particular condition. • Side effects are somewhat relative depending on the reason the drug is prescribed 15

16. Risk to Benefit Ratio • The prescribing physician must weigh the benefits from the use of a drug against the undesirable side effects when determining a suitable level of risk • The level of risk that is acceptable is related to the severity and the degree to which the condition is life threatening • Examples: Chemotherapy, Pain Killers etc 16

17. Tolerance • Over time the body adapts the presence of a drug • The person receiving the drug needs ever larger doses to achieve the original effect. • Tolerance results in increased risks of dependency/addiction • Increased risks of toxic levels • Possibility of immunity in anti-bacterials. 17

18. Thalidomide --An Example of Improper Drug Approval • Developed in Germany in the 1953. • Used as a tranquilizer (1957-1962). • Prescribed to combat morning sickness in the early months of pregnancy. • Marketed widely in Europe but never approved by the FDA in the USA. • Caused major birth defects in ABOUT 10,000 children whose mothers had taken thalidomide. 18

19. Thalidomide • Thalidomide has two optical isomers, one of which is a powerful teratogen. Chiral Carbon 19

20. Thalidomide Thalidomide is both a tranquilizer and a teratogen It is sometimes used to treat some symptoms of Hansen’s disease. (Leprosy) 20

21. Drug Classification • Drug Categories • Depressants • Stimulants • Antacids • Analgesics • Antibacterial • Antiviral • Mind Altering Drugs 21

22. Review • When defining drugs what are three ways in which drugs affect the body? • Explain the following: Therapeutic index, tolerance, the placebo effect, effective dose, lethal dose. • Outline the steps in bringing a drug to market. • What happened with the drug, thalidomide, that resulted in a major drug catastrophe? 22