Pharmacokinetics Overview Quiz
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Pharmacokinetics Overview Quiz

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Questions and Answers

Which drug is mentioned as having a volume of distribution greater than the total body volume?

  • Aspirin
  • Morphine (correct)
  • Acetaminophen
  • Ibuprofen

    • What is the primary reason haemodialysis is not effective for certain drugs mentioned?

  • They have a low volume of distribution
  • They are highly water-soluble
  • They are protein-bound
  • They have a volume of distribution greater than blood plasma (correct)

    • What role do plasma proteins play in the pharmacological activity of drugs?

  • They actively metabolize drugs
  • Only the bound portion of drugs is pharmacologically active
  • They bind only to highly hydrophilic drugs
  • The unbound portion of drugs is pharmacologically active (correct)

    • How might two drugs that bind to the same transporter proteins affect each other?

    <p>They will compete, possibly altering drug concentration</p> Signup and view all the answers

    Which body compartments can drugs distribute into based on their volume of distribution?

    <p>Extracellular compartments and fat tissue</p> Signup and view all the answers

    What is a significant factor affecting drug distribution in the body?

    <p>Plasma protein binding</p> Signup and view all the answers

    Which of the following describes the volume of distribution?

    <p>It is the total amount of drug in the body divided by plasma concentration.</p> Signup and view all the answers

    Which tissue is known to significantly affect drug distribution due to its storage capacity?

    <p>Adipose tissue</p> Signup and view all the answers

    What is the clinical significance of two drugs binding to the same transporter proteins?

    <p>It may lead to competitive inhibition affecting drug concentrations.</p> Signup and view all the answers

    Which barrier does NOT typically affect drug distribution?

    <p>Gastrointestinal barrier</p> Signup and view all the answers

    How does the unbound portion of a drug in the plasma differ from the bound portion?

    <p>The unbound portion is pharmacologically active.</p> Signup and view all the answers

    Which factor is NOT typically associated with influencing drug distribution in the body?

    <p>pH of the drug solution</p> Signup and view all the answers

    When considering the distribution around the body, which compartment is important to recognize?

    <p>Cerebrospinal fluid compartment</p> Signup and view all the answers

    What does plasma protein binding primarily impact regarding drugs?

    <p>The drug's pharmacological effect</p> Signup and view all the answers

    Which plasma protein is most important for drug binding?

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

    What influences the extent of plasma protein binding?

    <p>The concentration of free drug</p> Signup and view all the answers

    Why can't drugs bound to plasma proteins exert pharmacological effects?

    <p>They are unable to diffuse into cells</p> Signup and view all the answers

    In which scenario could competition for plasma protein binding sites occur?

    <p>When multiple drugs are administered that are bound to the same protein</p> Signup and view all the answers

    How is plasma protein binding expressed?

    <p>As a percentage of the plasma concentration</p> Signup and view all the answers

    Which of the following drugs is likely to have a high percentage of plasma protein binding?

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

    Which type of drugs do alpha-1-acid glycoproteins typically bind?

    <p>Basic drugs</p> Signup and view all the answers

    What primarily forms the blood-brain barrier (BBB)?

    <p>Tight junctions between capillary endothelial cells and glial cells</p> Signup and view all the answers

    Which type of molecules is most inhibited from penetrating the blood-brain barrier?

    <p>Polar and ionized molecules</p> Signup and view all the answers

    How does inflammation affect the blood-brain barrier?

    <p>It causes an overall increase in barrier permeability</p> Signup and view all the answers

    Which condition is associated with an increased concentration of drugs in the cerebrospinal fluid (CSF)?

    <p>Bacterial meningitis</p> Signup and view all the answers

    What factor does NOT impact drug transfer across the placenta?

    <p>Molecular weight of the drug</p> Signup and view all the answers

    Why are water-soluble and ionized drugs generally unable to cross the blood-brain barrier?

    <p>They cannot traverse the lipid cell membrane effectively</p> Signup and view all the answers

    In which scenario is drug accumulation highest in the placenta?

    <p>When the drug is highly lipophilic</p> Signup and view all the answers

    What characterizes the capillary endothelial cells in the brain, contributing to the blood-brain barrier?

    <p>They form tight junctions creating a continuous wall</p> Signup and view all the answers

    Which of the following statements about drug transport in the placenta is true?

    <p>ABC transporters facilitate the efflux of drugs from the placenta to the maternal circulation.</p> Signup and view all the answers

    What is a known therapeutic advantage of bisphosphonates?

    <p>They can adsorb onto bone and release slowly.</p> Signup and view all the answers

    Why are tetracycline antibiotics contraindicated during pregnancy?

    <p>They accumulate in the bone, potentially harming fetal development.</p> Signup and view all the answers

    Which drug has the highest volume of distribution (Vd) according to the provided data?

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

    What phenomenon occurs due to the pH difference between fetal and maternal plasma?

    <p>Ion trapping of basic drugs in fetal circulation.</p> Signup and view all the answers

    Which characteristic of certain drugs makes them less effectively removed by haemodialysis?

    <p>They have a high volume of distribution.</p> Signup and view all the answers

    What effect does binding drugs into body fat have on their volume of distribution?

    <p>It can increase the volume of distribution beyond total body water.</p> Signup and view all the answers

    Which of these drugs would likely accumulate in bone and serve as a slow release reservoir for toxins?

    <p>Heavy metals</p> Signup and view all the answers

    Study Notes

    Pharmacokinetics

    • Pharmacokinetics describes the movement of a drug in the body. It consists of absorption, distribution, metabolism, and excretion.
    • Distribution refers to how drugs move from the systemic circulation to the site of action.
    • Two factors are main contributors to drug distribution: plasma protein binding and tissue partitioning.
    • When studying pharmacokinetics, we study the movement of drug into, through, and out of the body in terms of 4 main characteristics: ADME
      • Absorption
      • Distribution
      • Metabolism
      • Excretion

    Plasma Protein Binding

    • Many drugs circulate in the bloodstream bound to plasma proteins.
    • This binding is reversible.
    • The extent of binding depends on the affinity of a particular drug for protein-binding sites.
    • Plasma protein binding (PPB) is expressed as a % of the plasma concentration.
      • For example, Warfarin is 99% PPB, meaning 99% of Warfarin in plasma is bound to plasma proteins; the remaining 1% is unbound and free to bind to receptors and be eliminated.

    Plasma Proteins

    • Albumin is the most important protein for drug binding and binds acidic drugs, including warfarin, NSAIDs, and sulfonamides.
    • ß-globulin and acid glycoproteins bind to basic drugs, such as quinine.

    ### Unbound Drug

    • Unbound drug is free in plasma, can bind to receptors, exerts a pharmacological effect, diffuses into interstitial fluid and cells, can be metabolized, and can be filtered at the glomerulus and excreted.

    Bound Drug

    • Bound drug is bound to plasma proteins, cannot bind to receptors, can't exert a pharmacological effect, cannot move from the plasma compartment, cannot be metabolized, and cannot be filtered at the glomerulus and excreted.

    Factors That Affect Plasma Protein Binding

    • Concentration of free drug.
    • Drug affinity for the binding sites.
      • Based on whether the drug is acidic or basic.
    • Concentration of plasma protein.
      • Disease states.
      • Drug-drug interactions due to competition for the same plasma protein binding sites.

    Blood-Brain Barrier (BBB)

    • The BBB is formed by tight junctions between the continuous layer of capillary endothelial cells, and glial cells that surround the capillaries.
    • The BBB inhibits the penetration of polar and ionised molecules into brain neurons.
    • This barrier limits access of many drugs to the central nervous system (CNS).

    Alteration of the BBB

    • Alteration to the permeability of the BBB can affect drug efficacy.
    • This can be caused by conditions such as inflammation, bacterial meningitis, bradykinins, and treatment for brain tumors.

    Placenta

    • The placenta is a selective barrier that protects the foetus from harmful effects of drugs.
    • Almost all drugs cross the placenta to a certain extent.
    • Some drugs accumulate in the placenta at levels exceeding those in maternal plasma.
    • Drug transfer across the placenta depends on:
      • Lipid solubility.
      • Extent of plasma binding.
      • Degree of ionisation.

    Bone

    • Certain drugs can accumulate in bone by adsorption onto the bone crystal surface and incorporation into the crystal lattice.
      • This includes tetracycline antibiotic, heavy metals (e.g., lead, radium), and bisphosphonates.
    • Bone can be a reservoir for the slow release of toxic agents, allowing effects to persist long after exposure.
      • For example, lead or radium can persist in the bone after exposure.

    ### Volume of Distribution

    • The volume of distribution (Vd) refers to the apparent volume into which a drug is distributed.
    • Vd is calculated by dividing the total amount of drug in the body by its plasma concentration.
    • Drugs with lower Vd tend to be found primarily in the plasma, while drugs with higher Vd are more widely distributed throughout the body.
    • Drugs with a Vd greater than the total body volume are not efficiently removed from the body by hemodialysis (blood filtration).

    Volume of Distribution Calculation

    • Heparin Vd = 0.07L/kg
    • Warfarin Vd=0.14L/kg
    • Aspirin Vd = 0.17L/kg
    • Amoxicillin Vd = 0.3L/kg
    • Valproic acid Vd 0.1 – 0.4L/kg
    • Paracetamol Vd = 0.9L/kg
    • Diazepam Vd = 0.8-1 L/kg
    • Fluoxetine Vd = 20-42L/kg

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    Pharmacology: Basic Principles and Distribution (PDF)

    Description

    This quiz covers essential concepts of pharmacokinetics, including drug absorption, distribution, metabolism, and excretion (ADME). It also highlights the role of plasma protein binding in drug circulation. Test your understanding of these fundamental topics in pharmacology.

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