Pharmacokinetics: Volume of Distribution
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Questions and Answers

What is the advantage of using extended-release tablets for oral morphine?

  • Bypass of the harsh gastrointestinal environment
  • Faster absorption
  • Reduced frequency of administration (correct)
  • Avoidance of first-pass metabolism

    • What are the advantages of sublingual and buccal routes of drug absorption?

  • First-pass metabolism
  • Ease of administration
  • Rapid absorption (correct)
  • GI tract instability

    • When is parenteral drug administration used?

  • For conscious patients only
  • For drugs stable in the GI tract
  • For drugs requiring rapid onset of action (correct)
  • For drugs that are well-absorbed from the GI tract

    • What are the benefits of parenteral routes of drug administration?

    <p>High bioavailability</p> Signup and view all the answers

    What is the formula for calculating the volume of distribution (Vd)?

    <p>Vd = C0</p> Signup and view all the answers

    In which compartment of the body is a drug effectively trapped if it has a high molecular weight or is extensively protein bound?

    <p>Plasma compartment</p> Signup and view all the answers

    Which type of drug distribution results in a low volume of distribution (Vd) that approximates the plasma volume?

    <p>Distribution into plasma compartment</p> Signup and view all the answers

    What does a low volume of distribution (Vd) indicate about the distribution of a drug in the body?

    <p>Trapping within the plasma compartment</p> Signup and view all the answers

    What is the energy source driving active transport of drugs across the cell membrane?

    <p>Hydrolysis of adenosine triphosphate (ATP)</p> Signup and view all the answers

    Which mechanism of drug absorption involves specific carrier proteins that span the cell membrane?

    <p>Active transport</p> Signup and view all the answers

    What type of absorption is used to transport drugs of exceptionally large size across the cell membrane?

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

    Which process involves cells using vesicle formation to secrete substances out of the cell?

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

    Which process involves drugs entering the kidney through renal arteries?

    <p>Glomerular filtration</p> Signup and view all the answers

    What is the normal glomerular filtration rate (GFR)?

    <p>125 mL/min</p> Signup and view all the answers

    What influences the passage of drugs into the glomerular filtrate?

    <p>Variations in GFR and protein binding of drugs</p> Signup and view all the answers

    Where do drugs that were not transferred into the glomerular filtrate leave the glomeruli?

    <p>Efferent arterioles</p> Signup and view all the answers

    What factor strongly influences the distribution of lipophilic drugs?

    <p>Blood flow to the area</p> Signup and view all the answers

    Which type of drug distribution may serve as a major source of the drug and prolong its actions or cause local drug toxicity?

    <p>Binding to tissue proteins</p> Signup and view all the answers

    What is the apparent volume of distribution (Vd) defined as?

    <p>The fluid volume required to contain the entire drug in the body at the same concentration measured in the plasma</p> Signup and view all the answers

    In drug distribution, drugs that accumulate in tissues may do so due to:

    <p>Binding to lipids, proteins, or nucleic acids</p> Signup and view all the answers

    In which clinical situation may a patient require a decrease in drug dosage or less frequent dosing?

    <p>Decreased metabolism due to a concomitant drug inhibiting metabolism</p> Signup and view all the answers

    Which abnormality is likely to result in an increase in drug half-life for a patient?

    <p>Decreased metabolism due to hepatic insufficiency as with cirrhosis</p> Signup and view all the answers

    What can result in the necessity of higher doses or more frequent dosing intervals for a drug?

    <p>Increased hepatic blood flow</p> Signup and view all the answers

    What factors influence the distribution of a drug from the plasma to the interstitium?

    <p>Blood flow, capillary permeability, tissue volume, binding of the drug to plasma and tissue proteins, and relative lipophilicity of the drug</p> Signup and view all the answers

    Why does propofol rapidly distribute into the central nervous system (CNS) when administered intravenously?

    <p>High blood flow and high lipophilicity of propofol</p> Signup and view all the answers

    What determines capillary permeability in the process of drug distribution?

    <p>Capillary structure and chemical nature of the drug</p> Signup and view all the answers

    Which factor partly explains the short duration of hypnosis produced by an IV bolus of propofol?

    <p>Variation in blood flow to tissue capillaries</p> Signup and view all the answers

    What does the volume of distribution (Vd) indicate about a drug that has a low Vd?

    <p>The drug has a low Vd that approximates the plasma volume</p> Signup and view all the answers

    In which compartment of the body would a drug with a low molecular weight but is hydrophilic distribute into?

    <p>Interstitial fluid</p> Signup and view all the answers

    What factor could lead to a drug having a high volume of distribution (Vd)?

    <p>Extensive protein binding and high molecular weight</p> Signup and view all the answers

    What does the volume of distribution (Vd) compare the distribution of a drug with?

    <p>Volumes of the water compartments in the body</p> Signup and view all the answers

    Why is the rectal route of drug administration advantageous in preventing drug destruction in the gastrointestinal (GI) environment?

    <p>Because it bypasses the portal circulation and minimizes biotransformation by the liver</p> Signup and view all the answers

    What is a significant disadvantage of the rectal route of drug administration?

    <p>Erratic and incomplete absorption of drugs</p> Signup and view all the answers

    How does the rate and extent of drug absorption vary for routes of administration other than intravenous?

    <p>They result in lower bioavailability due to incomplete absorption</p> Signup and view all the answers

    What does the absorption of drugs involve?

    <p>Transfer of a drug from the site of administration to the bloodstream</p> Signup and view all the answers

    What type of distribution does aminoglycoside antibiotics exhibit?

    <p>Distribution into the extracellular fluid</p> Signup and view all the answers

    What does a larger volume of distribution (Vd) generally indicate?

    <p>Greater distribution into tissues</p> Signup and view all the answers

    How is the apparent Vd defined?

    <p>Volume of drug distributed into the extracellular fluid</p> Signup and view all the answers

    What allows for the calculation of Vd in drug clearance?

    <p>First order drug elimination</p> Signup and view all the answers

    Which type of drug kinetics is most commonly observed for drug elimination?

    <p>First-order kinetics</p> Signup and view all the answers

    What allows the kidney to efficiently eliminate lipophilic drugs?

    <p>Increased polarity due to metabolism</p> Signup and view all the answers

    Which general set of reactions in the liver leads to the conversion of lipid-soluble agents into more polar substances?

    <p>Phase I and phase II reactions</p> Signup and view all the answers

    What must drugs be sufficiently polar to be, in order to be eliminated from the body?

    <p>Eliminated through urinary excretion</p> Signup and view all the answers

    What are the factors that influence the distribution of a drug from the plasma to the interstitium?

    <p>All of the above</p> Signup and view all the answers

    Why does propofol rapidly distribute into the central nervous system (CNS) when administered intravenously?

    <p>High blood flow and high lipophilicity</p> Signup and view all the answers

    What may partly explain the short duration of hypnosis produced by an IV bolus of propofol?

    <p>Low blood flow to skeletal muscles</p> Signup and view all the answers

    What determines capillary permeability in the process of drug distribution?

    <p>Capillary structure and chemical nature of the drug</p> Signup and view all the answers

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