Drugs and Medicines Version 1.05 1

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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