Pharmacology Introduction

1. Pharmacology Introduction

2. Terminology • Drug • Pure chemical compound with specific chemical structure • Biological effects • Chemical effects • Therapeutic Effect • Intended effect of a drug • Drug Indication • Therapeutic use of a drug • Contraindication • Situation when a particular drug should NOT be used

3. Undesired Effects of Drugs • Side Effects • Nuisance more than dangerous • E.g. dry mouth, sedation, • Adverse Effects • May be harmful • E.g. darrhea, vomitting, CNS disturbances • Toxic Effects • Drug poisoning • Most drugs exhibit all effects depending on dose

4. Basic Concepts • Site of Action • Location within the body where the drug exerts its therapeutic effect • E.g. aspirin acts at the hypothalamus to reduce fever • Mechanism of Action • How a drug produces its effects • Anesthetic produce loss of pain by interrupting sensory nerve conduction

5. Receptor Site • Drug usually exerts action once binding to specific cell in the body • Often site of binding is a specific receptor • Receptor site is usually synonymous with Site of Action • E.g. morphine binds to opiod receptors in the brain to reduce pain • Same receptors as endorphins in exercise or fight of flight

6. Agonists and Antogonists • Drugs that bind to specific receptors and produce a drug action are termed Agonists • Drugs that bind to specific receptors but do not produce any drug action are termed Antagonists • Antagonists are used as blocking drugs • Naloxone is an antogonist to morphine receptor • Used for treatment in morphine overdose

7. Dose-Response Curve • Dose is the exact amount of a drug that is administered in order to produce and effect • The graph of the response versus a given dose is the dose-response curve • The response is often proportional to the dose • Not always • May hit a ceiling above which no therapeutic effect is observed, but adverse effects may be • ED50 • Effective dose that elicits 50% of maximal response • Measure of potency

8. Agonist Dose Response Curves Full agonist Partial agonist Response Dose

9. Relative Potency hydromorphone morphine codeine Analgesia aspirin Dose

10. Effectiveness, toxicity, lethality • ED50 - Median Effective Dose 50; the dose at which 50 percent of the population or sample manifests a given effect; used with quantal dr curves • TD50 - Median Toxic Dose 50 - dose at which 50 percent of the population manifests a given toxic effect • LD50 - Median Toxic Dose 50 - dose which kills 50 percent of the subjects

11. Quantification of drug safety TD50 or LD50 Therapeutic Index = ED50

12. Drug A 100 sleep death Percent Responding 50 0 ED50 LD50 dose

13. Drug B 100 sleep death Percent Responding 50 0 ED50 LD50 dose

14. Time-Response Curve • Relationship of drug response and duration of the action

15. Drug Safety • All drugs will act as poisons if taken in excess • Therapeutic effect is distinguished from toxic effect by dose • Factors such as route of administration, absorption, and drug metabolism will influence amount of drug reaching site of action

16. Nomenclature • All drugs typically have three names • Chemical • Gives the chemical structure of the compound • Generic • Often abbreviated form of chemical name • Trade • Name given by manufacturer to drug

17. Drug Schedules • Schedule 1 • High abuse potential- no accepted medical use • E.g. heroin, not to be prescribed • Schedule 2 • High abuse potential – accepted medical use • E.g. morphine, cocaine, no refills without new prescription • Schedule 3 • Moderate abuse potential – accepted medical use • E.g. codeine plus another drug, can be refilled 5 x in 6 months • Schedule 4 • Low abuse potential – accepted medical use • E.g. valium, phenobarbital, can be refilled 5 x in 6 months • Schedule 5 • Limited abuse potential – accepted medical use No limitations on refill of prescription