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HLSC 3P19 (1)
Midterm

Objectives+for+exam1.doc

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Department
Health Sciences
Course
HLSC 3P19
Professor
Hui Di Wang
Semester
Fall

Description
For exam1: Chapter 1: Introduction to Pharmacology Chapter 2: Pharmacokinetics Objectives: Develop basic concepts for the terms: • Pharmacology • Pharmacokinetics: A-D-M-E • Pharmacodynamics(1): dose-response relationship • Pharmacodynamics(2): Drug, Receptor, Drug-Receptor Interaction, and signal transduction Absorption and Distribution: You should able to • List and discuss the factors affecting absorption • refers to the passage of drug from the site of administration into the general circulation, except when applied directly to tissue • Barriers: unless direct to circulation(IV), must cross cell membrane Oral administration: must pas through gut lumen, epithelium, interstitial fluid, capillary endothelium to get to blood (Figure 2-3 p10 Brenner) Drugs cross cell membrane • Passive diffusion (fick’s law), down gradient, non selective, non saturable • Fick’s Law: the rate of absorption is proportional to the dug concentration gradient across the barrier and the surface area available for absorption at that site Aqueous diffusion Lipid diffusion 1. Ionized form has high water solubility, can not cross CM, protonated weak base 2. Unionized has high lipid solubility, readily cross CM, protonated weak acid 3. ratio of the two forms influence the rate of absorption and is also a factor in distribution and elimination • Facilitated diffusion, down, selective, saturable • Active transport, against, selective, saturable, requires energy (ATP) • Predict the relative ease of permeation of a weak acid or base from a knowledge of its pKa and pH of the medium • HA (protonated form or uncharged) will prevail in a low pH (acidic). Ha a higher degree of lipid solubility than A- (unprotonated) • A- will prevail in a high pH, lower degree of lipid solubility • HB+ (protonated or uncharged) will prevail in low pH, lower degree of lipid solubility • B (unprotonated or charged) will prevail in high pH, higher degree of lipid solubility • List and discuss the common routs of drug administration Intravenous • Rate of absorption IMMEDIATE • Extent 100% Oral >>many barriers to absorb • Rate GRADUAL • Extent of absorption Incomplete • List and discuss the factors affecting distribution •From circulation to the target tissues •The reversible movement of drug between body compartments • The important factors that affect distribution from the general circulation to other tissue compartments are: – Solubility of the drug in that tissue – Small, uncharged and lipid soluble drugs will distribute faster and more widely than large, ionized, less lipid soluble drugs. – Blood flow – Capillary permeability o brain capillaries have tight junctions  only Lipophilic drugs diffuse, unless actively transported o liver and spleen, the capillaries are very leaky  leave capillaries regardless of lipid solubility, charged, polar Any others are between two extremes. – Plasma protein binding • Drugs differ in their tendency to bind to proteins in the blood • Binding is saturable. • Competition occurs between drugs binding to the same site on plasma proteins Compute the half-life of a drug based on its clearance and volume of distribution. A drug’s clearance is directly proportional to its volume of distribution and is inversely proportional to its half-life. T ½= 0.693/ke Cl=0.693 Vd/t ½ Learn the following definitions: Pharmacology: two subdivisions Pharmacokinetics • The study of what the body does to drugs Pharmacodynamics • The study of what drugs do to the body Dose of drug>>resulting drug concentration in the body over time>>mechanism & magnitude of drug effects Drugs: Contains a known quantity of an identified pure active substance. • Drugs are intended to have a selective action, but this ideal is seldom achieved. Absorption: refers to the passage of drug from the site of administration into the general circulation, except when applied directly to tissue. Bioavailability: how much of the administered dose that enters the general circulation (percent bioavailability= F) Area Under the curve (AUC): Bioavailability= (AUC oral/ AUC IV)*100 Distribution: • From circulation to the target tissues • The reversible movement of drug between body compartments • The important factors that affect distribution from the general circulation to other tissue compa
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