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 (A)</p> Signup and view all the answers

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

<p>Vd = C0 (B)</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 (A)</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 (D)</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 (A)</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) (D)</p> Signup and view all the answers

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

<p>Active transport (D)</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 (B)</p> Signup and view all the answers

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

<p>Exocytosis (B)</p> Signup and view all the answers

Which process involves drugs entering the kidney through renal arteries?

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

What is the normal glomerular filtration rate (GFR)?

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

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

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

What factor strongly influences the distribution of lipophilic drugs?

<p>Blood flow to the area (C)</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 (C)</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 (B)</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 (D)</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 (D)</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 (A)</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 (D)</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 (C)</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 (A)</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 (D)</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 (B)</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 (C)</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 (C)</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 (A)</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 (D)</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 (D)</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 (A)</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 (A)</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 (D)</p> Signup and view all the answers

What type of distribution does aminoglycoside antibiotics exhibit?

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

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

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

How is the apparent Vd defined?

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

What allows for the calculation of Vd in drug clearance?

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

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

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

What allows the kidney to efficiently eliminate lipophilic drugs?

<p>Increased polarity due to metabolism (D)</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 (D)</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 (A)</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 (D)</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 (D)</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 (D)</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 (A)</p> Signup and view all the answers

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