1. Principles of Pharmacology

2. SOURCES AND NAMES OF DRUGS Sources of Drugs Many drugs are isolated from plants or chemically derived from plant substances. Names of Drugs Chemical Name Chemical description of the molecule e.g., acetylsalicylic acid Generic Name The legal or official name, listed in the USP e.g., aspirin Brand Name Trademark belongs to the manufacturer e.g., Exedrin

3. CATEGORIES OF DRUGS AND DRUG IDENTIFICATION Drug Classification Systems Chemical Structure Pharmacological Actions Clinical/Behavioral Effects For our purposes, the most practical classification system is by effects on the user.

4. QUANTIFYING DRUG EFFECTS Pharmacodynamics the physiological actions of drugs Dose-Response Relationships Efficacy (ED 50 = median effective dose) Lethality (LD 50 = median lethal dose) Therapeutic Index = LD 50 /ED 50

5. DOSE RESPONSE FUNCTIONS

6. QUANTIFYING DRUG EFFECTS Potency The amount of drug required to produce a particular response NOT the same as efficacy Potencies of different drugs are compared by comparing the ED 50 ’s of each drug. Time-Dependent Factors in Drug Actions Several factors may prolong or maintain a drug’s effects.

7. DOSE RESPONSE FUNCTIONS

8. MOVEMENT OF DRUGS IN THE BODY Pharmacokinetics Several factors influence the movement of drugs through the body to target sites of action Pharmacokinetics is the study of factors that influence: Absorption from tissue sites to bloodstream Distribution throughout the body Metabolism (detoxification, breakdown) Elimination of metabolic waste products

9. DRUG ABSORPTION A Little Chemistry Lipid solubility pKa = pH at which 50% of drug molecules are ionized (charged). Only uncharged molecules are lipid soluble. The pKa of a molecule influences its rate of absorption through tissues into the bloodstream. pH varies among tissue sites (e.g., stomach pH is 3- 4, intestinal pH is 8-9)

10. DRUG ABSORPTION Routes of Administration Oral administration (P.O.) Injection (I.M., I.V., S.C., I.P.) Inhalation Other mucous membrane routes Intranasal, Sublingual, Rectal Topical (skin surface)

11. DRUG ABSORPTION Oral Drug Administration Advantages: relatively safe, economical, convenient, practical Disadvantages: Blood levels are difficult to predict due to multiple factors that limit absorption. Some drugs are destroyed by stomach acids. Some drugs irritate the GI system.

12. INJECTION ROUTES Advantages of Injection Routes Absorption is more rapid than with oral administration. Rate of absorption depends on blood flow to particular tissue site (I.P. > I.M. > S.C.). Advantages specific to I.V. injection No absorption involved (inject directly into blood). Rate of infusion can be controlled. A more accurate prediction of dose is obtained.

13. INJECTION ROUTES Disadvantages/Risks of Injection A rapid onset of action can be dangerous in overdosing occurs. If administered too fast, heart and respiratory function could collapse. Drugs insoluble in water or dissolved in oily liquids can not be given I.V. Sterile techniques are necessary to avoid the risk of infection.

14. Cell Membranes Capillaries Drug affinities for plasma proteins Bound molecules don’t cross capillary walls, while unbound molecules are free to pass through cell membranes to sites of action Blood Brain Barrier Tight junctions in capillaries plus glial cells surrounding capillaries Less developed in infants Cerebral trauma can decrease integrity of BBB Placenta Not a barrier to lipid soluble substances. DRUG DISTRIBUTION

15. DRUG DEACTIVATION Metabolism and Excretion Liver microsomal enzymes Drug metabolism differs by age and gender due to differences in microsomal enzyme systems. Two-stage kidney process (filter, absorption) Some drugs have active (lipid soluble) metabolites.

16. DRUG DEACTIVATION Drug Half-Life The half-life of a drug is the amount of time required for half the drug to be eliminated from the body. A drug with a half-life of 30 minutes is eliminated. It takes approximately 6 half-lives for a single drug dose to be eliminated. Some drugs are eliminated at a constant rate, and therefore do not have half-lives (e.g. alcohol).