Pharmacology Introduction

Terminology Drug Therapeutic Effect Drug Indication Contraindication 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

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

Basic Concepts Site of Action Mechanism 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

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

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

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

Agonist Dose Response Curves Full agonist Partial agonist Response Dose

Relative Potency hydromorphone morphine codeine Analgesia aspirin Dose

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

Quantification of drug safety TD50 or LD50 Therapeutic Index = ED50

Drug A 100 sleep death Percent Responding 50 ED50 LD50 dose

Drug B 100 sleep death Percent Responding 50 ED50 LD50 dose

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

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

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

Drug Schedules Schedule 1 Schedule 2 Schedule 3 Schedule 4 Schedule 5 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