Pharmacokinetics Overview
27 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What characterizes the distribution of a drug that has central and peripheral compartments?

  • Drugs can only move from the central to the peripheral compartment.
  • Equilibrium is established quickly between plasma and tissue.
  • Elimination occurs from the peripheral compartment.
  • Drugs can move to and from the peripheral compartment back to the central compartment. (correct)

    • Which statement accurately describes first order elimination kinetics?

  • The rate of decrease in drug concentration is constant regardless of the amount in the body.
  • A constant fraction of the drug is eliminated at any given time. (correct)
  • A constant amount of drug is eliminated independent of dose.
  • The elimination rate is dependent on the dose administered.

    • In a semi-log plot for first order kinetics, what does the graphical representation look like?

  • An upward sloping line.
  • A straight linear line. (correct)
  • A parabolic curve.
  • A horizontal line.

    • What is true regarding zero order elimination kinetics?

    <p>A constant amount of drug is eliminated independent of the dose.</p> Signup and view all the answers

    What does bioavailability refer to in pharmacokinetics?

    <p>The fraction of unchanged drug reaching systemic circulation.</p> Signup and view all the answers

    What is the bioavailability of drugs administered intravenously?

    <p>1</p> Signup and view all the answers

    In a first order elimination process, which equation best describes the relationship between drug concentration and time?

    <p>C = (dose/Vd) e-kt</p> Signup and view all the answers

    What does the term 'bioavailability' in pharmacokinetics refer to?

    <p>The rate and extent to which the active ingredient or active moiety is absorbed and becomes available at the site of action.</p> Signup and view all the answers

    In a one-compartment model, what happens to the plasma concentration of a drug when it follows first-order kinetics?

    <p>The plasma concentration decreases exponentially.</p> Signup and view all the answers

    How is the elimination rate constant related to the half-life of a drug?

    <p>The half-life is inversely proportional to the elimination rate constant.</p> Signup and view all the answers

    What is a key characteristic of a two-compartment model?

    <p>Drug distribution occurs rapidly followed by a slower elimination phase.</p> Signup and view all the answers

    What is the primary principle of pharmacokinetics regarding drug effects?

    <p>The effect of a drug is related to the blood concentration of the drug.</p> Signup and view all the answers

    What is the purpose of administering a drug by IV and another route for comparison?

    <p>To measure plasma concentrations over time</p> Signup and view all the answers

    How is bioavailability generally expressed mathematically?

    <p>AUC oral / AUC iv</p> Signup and view all the answers

    What is the percent of a drug remaining in the body after three half-lives?

    <p>12.5%</p> Signup and view all the answers

    What does bioavailability indicate when a drug is administered orally?

    <p>The extent of absorption and/or first pass effect</p> Signup and view all the answers

    What does the half-life of a drug represent?

    <p>The time for a 50% decrease in plasma drug concentration</p> Signup and view all the answers

    Which of the following describes the volume of distribution (Vd) of a drug?

    <p>It reflects the apparent volume a drug would occupy in body fluids at equilibrium.</p> Signup and view all the answers

    After four half-lives, what fraction of the drug remains in the body?

    <p>0.06</p> Signup and view all the answers

    What formula is used to calculate the half-life of a drug in a one compartment model?

    <p>t1/2 = 0.693 / ke</p> Signup and view all the answers

    Which statement is true regarding drugs with high volume of distribution?

    <p>They indicate a drug is highly lipophilic or has low protein binding.</p> Signup and view all the answers

    What is a characteristic of half-life when determined graphically?

    <p>It can be illustrated using a semi-log plot</p> Signup and view all the answers

    What is the formula used to calculate the fraction of a drug eliminated from the body?

    <p>Fraction eliminated = 1 - 1/(2n)</p> Signup and view all the answers

    In the equation Ct = C0 e(-kxt), what does Ct represent?

    <p>Plasma concentration at time t</p> Signup and view all the answers

    Why is bioavailability important in pharmacology?

    <p>It allows for comparisons of different products with the same active ingredients</p> Signup and view all the answers

    What does the area under the curve (AUC) indicate in pharmacokinetics?

    <p>The extent of the drug's absorption into the bloodstream</p> Signup and view all the answers

    What factor may influence the bioavailability of a drug when it is administered orally?

    <p>Influence of food or other drugs</p> Signup and view all the answers

    Study Notes

    Pharmacokinetics Overview

    • Pharmacokinetics quantifies relationships among absorption, distribution, and elimination of drugs over time.
    • Blood concentration of a drug is directly related to its therapeutic effect, influencing efficacy and safety.

    Key Pharmacokinetic Parameters

    • Bioavailability (F): Fraction of unchanged drug reaching systemic circulation post-administration; intravenous (IV) drugs have F = 1, others < 1.
    • Half-Life (t1/2): Time required for plasma drug concentration to decrease by 50%; determined using ke (elimination rate constant).
    • Clearance (CL): Volume of plasma cleared of drug per unit time; inversely related to steady-state concentration.
    • Volume of Distribution (Vd): Apparent volume in which drug distributes; large Vd indicates high lipophilicity or low protein binding.
    • Elimination Rate Constant (ke): Rate at which drug concentration decreases over time; key in predicting drug clearance.
    • Steady State Concentration (Css): Stable level of drug in the body during continuous administration; reached after 4-5 half-lives.

    Compartment Models

    • One-Compartment Model: Assumes rapid equilibrium between plasma and tissues; characterized by linear decline in plasma concentration in semi-log plots.
    • Two-Compartment Model: Drug distributes between a central and a peripheral compartment; displays a biphasic decline in plasma concentration.

    Kinetics

    • First Order Kinetics: Rate of drug elimination is proportional to its concentration; results in a linear semi-log plot.
    • Zero Order Kinetics: Constant amount of drug eliminated regardless of concentration; occurs when elimination pathways are saturated.

    Relationship Between Parameters

    • Clearance, half-life, volume of distribution, and plasma concentration are interrelated, affecting drug dosing and frequency.
    • Decreases in clearance will double Css if dosing rate remains constant.

    Calculating Pharmacokinetic Parameters

    • Formulas:
      • Half-Life: t1/2 = 0.693 / ke
      • Clearance: CL = Dose / Css
      • Bioavailability: F = AUC (oral) / AUC (IV)
    • Volume of Distribution calculation: Vd = Dose / (Css x ke).

    Practical Applications

    • Administer IV loading doses considering volume of distribution to achieve desired Css levels quickly.
    • Importance of bioavailability assessment for effective drug formulation comparison and understanding absorption variability.

    Additional Information

    • Four half-lives rule: After 4 half-lives, a drug is considered essentially eliminated, retaining only 6% in the body.
    • Knowledge of pharmacokinetics is crucial for appropriate drug therapy management, individualization of dose regimens, and optimization of therapeutic outcomes.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Pharmacokinetics PDF

    Description

    This quiz covers the key concepts and parameters in pharmacokinetics, including bioavailability, half-life, clearance, and volume of distribution. Understanding these parameters is essential for evaluating drug efficacy and safety. Test your knowledge of how drugs are absorbed, distributed, and eliminated from the body.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser