Pharmacokinetics Overview
32 Questions
0 Views

Pharmacokinetics Overview

Created by
@ExultantDramaticIrony7932

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What does pharmacokinetics primarily refer to?

  • The body's processing of a drug (correct)
  • The chemical composition of drugs
  • The therapeutic uses of drugs
  • The effects of drugs on the body

    • Which of the following pharmacokinetic properties involves the transfer of a drug from the site of administration into plasma?

  • Absorption (correct)
  • Metabolism
  • Distribution
  • Elimination

    • What is the primary mechanism through which 99% of drugs are absorbed?

  • Passive diffusion (correct)
  • Endocytosis
  • Facilitated diffusion
  • Active transport

    • What does a higher bioavailability generally indicate about a drug's administration?

    <p>Complete absorption into the bloodstream</p> Signup and view all the answers

    Which pharmacokinetic process involves biotransformation primarily by the liver?

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

    Which route of drug administration typically results in 100% bioavailability?

    <p>Intravenous injection</p> Signup and view all the answers

    Which factor does NOT influence the rate and extent of drug absorption?

    <p>The storage conditions of the drug</p> Signup and view all the answers

    What happens to drugs administered through routes other than intravenous?

    <p>They experience partial absorption</p> Signup and view all the answers

    What is the condition for a weak acid to cross the cell membrane effectively?

    <p>It must be in its uncharged form.</p> Signup and view all the answers

    How does pH influence the absorption of weak acids and bases?

    <p>The ratio of charged and uncharged forms is determined by pH.</p> Signup and view all the answers

    Which of the following statements about ionization constants (pKa) is true?

    <p>pKa is a measure of a drug's interaction strength with a proton.</p> Signup and view all the answers

    Which statement best describes the form of a weak base that is able to penetrate the cell membrane?

    <p>The uncharged form (B).</p> Signup and view all the answers

    What characteristic makes lipid-soluble drugs able to cross cell membranes?

    <p>They are nonpolar and non-ionic.</p> Signup and view all the answers

    How does the redistribution equilibrium of a drug occur in the body?

    <p>When the uncharged form reaches equal concentrations in all spaces.</p> Signup and view all the answers

    What is the consequence of a drug being ionized?

    <p>It becomes polar and cannot cross lipid membranes.</p> Signup and view all the answers

    What determines the effective concentration of a drug at its absorption site?

    <p>The relative concentrations of charged and uncharged forms.</p> Signup and view all the answers

    What is the main characteristic of facilitated diffusion?

    <p>It involves conformational changes of carrier proteins.</p> Signup and view all the answers

    Which process is used to transport large drugs across the cell membrane?

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

    What role does ATP play in active transport?

    <p>ATP provides energy to move substances against their gradient.</p> Signup and view all the answers

    Which factor does NOT influence drug absorption?

    <p>Type of drug carrier in the bloodstream</p> Signup and view all the answers

    Why might facilitated diffusion be inhibited?

    <p>By competition with other substances for the carrier proteins.</p> Signup and view all the answers

    What is true about the ionization of most drugs?

    <p>Most drugs are either weak acids or weak bases.</p> Signup and view all the answers

    Exocytosis is primarily responsible for which of the following?

    <p>Releasing neurotransmitters from nerve terminals.</p> Signup and view all the answers

    Which statement about lipid-soluble drugs is correct?

    <p>They can pass directly into cells without a carrier.</p> Signup and view all the answers

    What is the effect of a lower pKa value on a drug's acidity?

    <p>It indicates the drug is more acidic.</p> Signup and view all the answers

    How does the pH of the stomach affect the absorption of aspirin?

    <p>Aspirin is well absorbed in acidic pH, such as 1.5.</p> Signup and view all the answers

    In which pH environment is aspirin poorly absorbed?

    <p>pH 8.5</p> Signup and view all the answers

    What happens to aspirin in the gastric cells when pH rises to 7.4?

    <p>It becomes ionized and is trapped inside the cells.</p> Signup and view all the answers

    How can alkaline agents like sodium bicarbonate be used in relation to aspirin toxicity?

    <p>They enhance the elimination of aspirin by increasing ionization.</p> Signup and view all the answers

    Why is it important to know the pKa of drugs in clinical settings?

    <p>To assess potential absorption sites and toxicity management.</p> Signup and view all the answers

    What effect does blood flow have on drug absorption in the intestines compared to the stomach?

    <p>Higher blood flow in the intestines facilitates better absorption.</p> Signup and view all the answers

    What general principle can be inferred about drug absorption based on the pH of the environment?

    <p>Drug absorption is determined by the ionization state influenced by pH.</p> Signup and view all the answers

    Study Notes

    Pharmacokinetics

    • Pharmacokinetics describes what the body does to a drug, pharmacodynamics describes what the drug does to the body.
    • Four properties impact the effectiveness of a drug:
      • Absorption
      • Distribution
      • Metabolism
      • Elimination
    • These properties together are known as ADME.
    • Absorption is the movement of a drug from its administration site to the bloodstream.
    • Distribution involves the drug leaving the bloodstream and moving to interstitial and intracellular fluids.
    • Metabolism is the process of the drug being biotransformed by the liver or other tissues.
    • Elimination is the removal of the drug and its metabolites from the body via urine, bile, or feces.

    Absorption

    • The rate and extent of absorption depend on the environment where the drug is absorbed, chemical properties of the drug, and route of administration.
    • Intravenous injection delivers the drug directly to the bloodstream, resulting in 100% bioavailability.
    • Other routes of administration may result in partial absorption and lower bioavailability.

    Mechanisms of Absorption from the GI Tract

    • Passive Diffusion: the most common mechanism (~99% of drugs).
      • Drugs move from high to low concentration.
      • It's not carrier-mediated and does not require energy.
      • Water-soluble drugs penetrate through aqueous channels, lipid-soluble drugs readily move through lipid bilayers.
    • Facilitated Diffusion: carrier protein mediated, allowing the passage of large molecules through membranes, does not require energy.
    • Active Transport: energy-dependent (ATP hydrolysis), moves drugs against a concentration gradient, has saturation kinetics, and can be competitively inhibited by other molecules.
    • Endocytosis and Exocytosis: Processes for transporting larger-sized molecules across cell membranes.
      • Endocytosis: engulfment and transport into the cell.
      • Exocytosis: the reverse of endocytosis.
      • Vitamin B12 is transported via endocytosis, neurotransmitters (norepinephrine) are released by exocytosis.

    Factors Influencing Absorption

    • pH Effect on Drug Absorption:
      • Most drugs are weak acids or weak bases.
      • Drugs pass through membranes more readily in their uncharged form.
      • The ratio of charged to uncharged forms is determined by the pKa of the drug and pH of the environment.
      • For weak acids: uncharged HA form permeates membranes readily, while the charged A− does not.
      • For weak bases: uncharged B form permeates readily, while charged BH+ does not.
      • Aspirin is an acidic drug with a pKa of 3.5.
      • In the stomach (pH=1.5), aspirin is mainly uncharged (HA) and absorbed efficiently (~99%).
      • In the small intestine (pH=8.5), aspirin is mostly charged (A-) and poorly absorbed (~1%).
      • Aspirin is prone to causing peptic ulcers due to its high absorption in the acidic stomach environment and trapping of ionized aspirin in gastric cells.
    • Clinical Significance of pKa:
      • Determines absorption site.
      • Used to treat drug toxicity: e.g., alkalinizing agents (sodium bicarbonate) increase the ionization of acidic drugs, promoting elimination.
      • In breastfeeding: alkaline drugs may be well absorbed by the mother, but may not readily pass into breast milk due to ionization.
    • Blood Flow:
      • Intestines receive higher blood flow than the stomach, resulting in greater absorption.
      • Shock can severely reduce blood flow to subcutaneous tissues, decreasing absorption from subcutaneous administration.

    Other Factors

    • Surface Area: Larger surface area increases absorption.
    • Time: Drug absorption requires sufficient time for adequate transfer.
    • P-glycoprotein: A protein involved in drug efflux, can reduce drug absorption.
    • Lipid Solubility: Lipid-soluble drugs permeate cell membranes easily.
    • Ionization: Ionized drugs are less permeable across membranes.

    Studying That Suits You

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

    Quiz Team

    Related Documents

    Pharmacokinetics (Lec. I) PDF

    Description

    This quiz explores the fundamental concepts of pharmacokinetics, including the ADME properties: Absorption, Distribution, Metabolism, and Elimination. Understand how these properties affect drug effectiveness and the processes involved in each stage. Test your knowledge on the factors influencing drug absorption and the significance of different administration routes.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser