Slide 1. Slide 2. Slide 3. Drug Action and Handling. Lesson 2.1. Lesson 2.1. Drug Action and Handling. Drug Action and Handling.

Transcription

1 Slide 1 Drug Action and Handling Chapter 2 1 Slide 2 Lesson 2.1 Drug Action and Handling 1. Differentiate dose, potency, and efficacy in the context of the actions of drugs. 2. Explain the pharmacologic effect of a drug. 3. Discuss the major steps of pharmacokinetics: absorption, distribution, metabolism, and excretion. 4. Explain how altering absorption, distribution, metabolism, and excretion can affect clinical pharmacokinetics. 2 Slide 3 Lesson 2.1 Drug Action and Handling 5. Explain how half-life relates to clinical pharmacokinetics. 6. Provide an example of factors that may alter the effect of a drug. 7. Summarize the various routes of drug administration and the common dose forms used. 3

2 Slide 4 Drug Handling Drug: A biologically active substance that can modify cellular function 4 Slide 5 Characterization of Drug Action Dose-response curve Log dose effect curve Potency Efficacy 5 Slide 6 Log Dose Effect Curve 6

3 Slide 7 Log Dose Effect Curve (Cont.) 7 Slide 8 Characterization of Drug Action: Potency Potency of a drug is a function of the amount of the drug required to produce an effect 8 Slide 9 Characterization of Drug Action: Potency (Cont.) 9

4 Slide 10 Characterization of Drug Action: Efficacy Efficacy is the maximum intensity of effect or response that can be produced by a drug 10 Slide 11 Mechanism of Action of Drugs Pharmacologic effect Produce same action as endogenous agent Block action of endogenous agent Therapeutic effect Adverse effect 11 Slide 12 Agonists and Antagonists Agonist Has affinity for a receptor Combines with the receptor Produces an effect Antagonist Counteracts the action of the agonist 12

5 Slide 13 Agonists and Antagonists (Cont.) 13 Slide 14 Pharmacokinetics Pharmacokinetics is the study of how a drug enters the body, circulates within the body, is changed by the body, and leaves the body 14 Slide 15 Pharmacokinetics: Drug Absorption Mechanisms of drug transfer Passive transfer Simple diffusion Specialized transport Active transport Facilitated diffusion 15

6 Slide 16 Drug Absorption By Passive Transfer 16 Slide 17 Pharmacokinetics: Drug Distribution Distribution is the passage of drugs into various body fluid compartments such as plasma, interstitial fluids, and intracellular fluids 17 Slide 18 Pharmacokinetics: Drug Metabolism Metabolism or biotransformation is the body s way of changing a drug so that it can be more easily excreted by the kidneys 18

7 Slide 19 Pharmacokinetics: Drug Metabolism (Cont.) Metabolism mechanisms: Active to inactive Inactive to active Active to active 19 Slide 20 Pharmacokinetics: Excretion Renal (kidney) Lungs Bile Gastrointestinal tract Sweat Saliva Milk 20 Slide 21 Pharmacokinetics: Renal Excretion Glomerular filtration Active tubular secretion Passive tubular diffusion 21

8 Slide 22 Pharmacokinetics: Drug Absorption Factors that influence rate of drug absorption: Physicochemical properties Site of absorption Solubility of drug 22 Slide 23 Pharmacokinetics: Drug Absorption (Cont.) Factors that affect drug absorption and clinical pharmacokinetics: Presence of infection Dose form Drug solubility Blood flow at injection site 23 Slide 24 Pharmacokinetics: Drug Distribution Factors that determine distribution of drug: Organ size Blood flow to organ Drug solubility Plasma protein-binding capacity Presence of barriers 24

9 Slide 25 Pharmacokinetics: Drug Metabolism Factors that affect drug metabolism: Impaired liver function Hepatic portal circulation Drugs and environmental substances Inhibitors of cytochrome P Slide 26 Clinical Pharmacokinetics: Half-Life Drug half-life: The time it takes for the concentration of a drug to fall to one-half (50%) of its original blood level 26 Slide 27 Half-Life First-Order Kinetics 27

10 Slide 28 Half-Life Zero-Order Kinetics 28 Slide 29 Altering Drug Effects Patient adherence Gender Psychological factors Genetic variation Pathologic state Drug interactions Time of administration Age and weight Route of Environment administration Other 29 Slide 30 Routes of Administration Dose Forms Onset: Time it takes for the drug to begin to have its effect Duration: The length of time of a drug s effect 30

11 Slide 31 Enteral Parenteral Injection Inhalation Topical Routes of Administration Dose Forms (Cont.) 31 Slide 32 Oral Route of Drug Administration Advantages Small intestine presents large absorbing area Produces a slower onset of action Disadvantage Nausea, vomiting Certain drugs are inactivated by GI tract acidity or enzymes Drug interactions Requires patient cooperation 32 Slide 33 Rectal Route of Administration Advantages Used if patient is vomiting or unconscious Produces local or systemic effect Disadvantages Drugs are poorly and irregularly absorbed Poor patient acceptance 33

12 Slide 34 Intravenous Route of Drug Administration Advantages Produces most rapid drug response Produces predictable response Use in emergency situations Disadvantages Phlebitis Drug irretrievability Allergy Side effects related to high plasma concentrations 34 Slide 35 Advantages Intramuscular Route of Drug Administration Allows increased tolerance to irritating drugs Allows injection of suspensions, which provides a sustained effect 35 Slide 36 Subcutaneous Route of Drug Administration Injection of drugs into the subcutaneous areolar tissue Disadvantage Irritating solutions may cause sterile abscesses 36

13 Slide 37 Other Routes of Drug Administration Intradermal Intrathecal Intraperitoneal 37 Slide 38 Inhalation Route of Drug Administration Examples: Inhalers used to treat asthma, general anesthetics, nitrous oxide/oxygen Advantages Rapid onset of action Lack of need for needles Disadvantage Popular route for abuse of drugs 38 Slide 39 Topical Route of Drug Administration Advantages Systemic side effects are rare Disadvantages Increased risk of systemic side effects if surfaces are large and/or abraded, inflamed, or sloughing Intraorally spayed anesthetics may be absorbed into blood stream 39

14 Slide 40 Questions? 40