Drug Distribution Overview
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Questions and Answers

Which of the following factors does NOT directly influence the distribution of drugs in the body?

  • Ionization (pKa)
  • Organ blood flow
  • Binding to plasma and tissue proteins
  • Environmental temperature (correct)

    • How does the binding of a drug to plasma proteins affect its distribution and activity?

  • Bound drug is active and readily diffuses to target tissues.
  • Bound drug is inactive and acts as a reservoir for the drug. (correct)
  • Bound drug is active and rapidly metabolized by the liver.
  • Bound drug is inactive and increases the drug's elimination rate.

    • Which of the following accurately describes the relationship between free drug and bound drug in the body?

  • Bound drug is always more abundant than free drug.
  • Free drug is always more abundant than bound drug.
  • Bound drug is the active form and in equilibrium with free drug.
  • Free drug is the active form and in equilibrium with bound drug. (correct)

    • What is the primary reason why drugs are distributed rapidly to the brain, heart, liver, and kidney?

    <p>These organs are highly perfused with blood. (C)</p> Signup and view all the answers

    Which of the following conditions can affect drug distribution by altering the blood flow to tissues?

    <p>Congestive Heart Failure (CHF) (B)</p> Signup and view all the answers

    What is the relationship between drug binding to plasma proteins and the volume of distribution (Vd)?

    <p>Drugs with a high Vd are usually not bound to plasma proteins. (B)</p> Signup and view all the answers

    Which of the following factors can affect the volume of distribution (Vd) of a drug?

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

    Which of the following compartments is responsible for drug's movement to the peripheral compartments, and why?

    <p>Interstitial compartment, as it acts as a bridge between the bloodstream and cells. (E)</p> Signup and view all the answers

    Which of the following statements is TRUE about drug distribution?

    <p>The distribution of drugs is mainly determined by the free form of the drug in each compartment. (B)</p> Signup and view all the answers

    How does lipid solubility impact drug distribution, particularly to the brain?

    <p>Lipid-soluble drugs are easily transported across the blood-brain barrier, while polar molecules are restricted. (C)</p> Signup and view all the answers

    What is the primary mechanism by which drugs are distributed to different organs and tissues?

    <p>A combination of passive diffusion and active transport, with different mechanisms playing roles in different tissues. (C)</p> Signup and view all the answers

    What is the role of 'ion trapping' in drug distribution?

    <p>It enhances the concentration of drugs within certain compartments by trapping them in their ionized form. (D)</p> Signup and view all the answers

    According to the provided information, how does drug distribution influence the onset of drug action?

    <p>Drug distribution affects the onset of action by ensuring the concentration of the drug reaches the target site in a timely and sufficient manner. (E)</p> Signup and view all the answers

    What is the approximate percentage of total body water allocated to the interstitial compartment?

    <p>25% (D)</p> Signup and view all the answers

    Which of the following factors is LEAST directly involved in drug distribution?

    <p>Drug metabolism (C)</p> Signup and view all the answers

    Which drug accumulates in the heart tissue?

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

    What effect does inflammation have on the blood-brain barrier?

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

    Which of the following drugs does NOT cross the blood-brain barrier?

    <p>Water-soluble drugs (A)</p> Signup and view all the answers

    Which statement regarding the apparent volume of distribution (Vd) is correct?

    <p>Vd equals the dose divided by plasma concentration (A)</p> Signup and view all the answers

    What is a characteristic of the placental barrier?

    <p>Allows lipophilic drugs to pass freely (D)</p> Signup and view all the answers

    Which statement about absorption of weak acidic drugs is true?

    <p>They are more readily absorbed in acidic environments (C)</p> Signup and view all the answers

    Which of the following drugs is known for accumulation in the retina?

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

    Which factor could limit the bioavailability of oral drugs?

    <p>First-pass metabolism (C)</p> Signup and view all the answers

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    Flashcards

    Ionization (pKa)

    A measure of a drug's tendency to donate protons, affecting its solubility and distribution. Large molecules like heparin are impacted by this.

    Organ Blood Flow

    Drugs distribute rapidly to organs with high blood flow (e.g., brain, liver), leading to quicker action in these areas.

    Free vs Bound Drug

    Free drugs are active and available for metabolism, while bound drugs (attached to proteins like albumin) are inactive reservoirs.

    Plasma Protein Binding

    Drugs reversibly bind to plasma proteins, creating equilibrium between bound (inactive) and free (active) forms.

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    Effect of Disease on Drug Distribution

    Conditions such as CHF, uremia, and cirrhosis can alter drug distribution, affecting drug effectiveness and metabolism.

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    Drug Distribution

    The movement of drug from blood to tissues in the body.

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    Central Compartment

    The area primarily consisting of blood where drugs enter circulation.

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    Peripheral Compartment

    Areas outside the blood where drugs go, like tissues.

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    Lipid Solubility

    The ability of a drug to dissolve in fats, affecting its distribution.

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    Ion Trapping

    A process where drugs are concentrated in cells due to ionization.

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    Blood-Brain Barrier (BBB)

    A protective barrier limiting drug access to the brain.

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    Extracellular Fluid

    Fluid outside of cells, including interstitial and plasma volumes.

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    Free Drug

    Unbound drug molecules able to move between compartments.

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    Acidic Drugs

    Drugs that bind primarily to albumin in plasma.

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    Basic Drugs

    Drugs that bind primarily to α-1 glycoprotein and β-globulins.

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    Volume of Distribution (Vd)

    The volume that would contain the total drug at plasma concentration.

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    Significance of High Binding

    Drugs highly bound to proteins last longer but have lower activity.

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    Drug Displacement Interactions

    When two drugs compete for the same binding site on plasma proteins.

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    Hypoalbuminemia

    A condition with low albumin levels leading to increased free drug concentration.

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    Clinical Relevance of Vd

    Larger Vd indicates broader drug distribution, impacting treatment effectiveness.

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    Tissue Drug Accumulation

    Certain drugs accumulate in specific body tissues; e.g., Digoxin in the heart.

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    Effects of Inflammation on BBB

    Inflammation can disrupt BBB integrity, allowing normally restricted substances to enter.

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    Placental Barrier

    Allows lipophilic drugs to cross; sometimes even water-soluble drugs at high concentrations.

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    Ionization and Drug Absorption

    Un-ionized molecules cross membranes more easily than ionized forms, affecting absorption.

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    First-Pass Metabolism

    The liver metabolizes drugs before they reach systemic circulation, limiting bioavailability.

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    Plasma Protein Bound Drugs

    Drugs that are bound to proteins like albumin are inactive and can affect availability.

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    Study Notes

    Drug Distribution Overview

    • Drug distribution is crucial for drug action, moving drugs from the bloodstream to tissues.
    • Drugs travel to organs and tissues via circulation, diffusing into interstitial fluid and cells.
    • Most drugs aren't evenly distributed throughout the body; some are limited to extracellular fluid or plasma.
    • Lipid-soluble drugs diffuse through membranes easily.
    • Ion trapping concentrates other drugs within cells.
    • Active transport moves some drugs into cells.

    Drug Distribution and Body Water

    • Body water is divided into four compartments: plasma, interstitial, and intracellular fluids.
    • Drug molecules exist in bound or free forms; only free drugs move between compartments.
    • Plasma volume is about 0.05 liters per kilogram of body weight.
    • Plasma, interstitial, and intracellular fluids have differing compositions.

    Factors Affecting Drug Distribution

    • Lipid solubility is key, impacting penetration into tissues like the brain(blood-brain barrier).
    • Ionization (pKa) and molecular size also affect distribution, with large molecules often staying in the plasma.
    • Organ blood flow influences distribution speed, with highly perfused tissues receiving drugs faster (e.g., brain, heart, liver).
    • Binding to plasma and tissue proteins influences drug action (bound drug is inactive)
    • Illness like congestive heart failure, uremia, and cirrhosis affect drug distribution rates.

    Drugs Accumulated in Tissues

    • Certain drugs accumulate in specific organs or tissues.
    • Heart (Digoxin), Liver (Chloroquine), Thyroid (Iodine), Retina (Chloroquine), and Bone/teeth (Tetracycline).
    • Tissue accumulation can significantly alter the volume of distribution.

    Barriers to Drug Distribution

    • Blood-brain barrier (BBB) and placental barriers restrict drug entry into the brain and fetus.
    • BBB consists of tightly connected endothelial cells, preventing many drugs with low lipid solubility from crossing.
    • Inflammation can disrupt the BBB, allowing drug entry.
    • Placental barriers are also present but aren't fully developed and aren't completely impenetrable to some drugs,

    Plasma Protein Binding of Drugs

    • Drugs can bind to plasma proteins (mostly albumin), affecting their distribution and action.
    • Acidic drugs typically bind to albumin, while basic drugs often bind to alpha-1 glycoprotein.
    • This binding can significantly impact a drug's activity.
    • Highly bound drugs stay in the blood longer and have less therapeutic effect.
    • Also, bound drugs are unavailable for dialysis or other removal methods; free drug is the pharmacologically active form.
    • Drug interactions may occur if multiple drugs compete for the same binding sites, displacing each other and raising free drug concentrations of the less strongly bound drug.

    Volume of Distribution (Vd)

    • Apparent volume of distribution (Vd) is the theoretical volume that would contain the drug at the same concentration as in the plasma.
    • Larger Vd indicates wider distribution of the drug in the body,
    • The plasma volume is about 0.05 liters/kg in a typical healthy adult.
    • Vd is calculated as the administered dose divided by the plasma concentration.
    • Vd isn't determined entirely by the drug's property but is impacted by binding with plasma proteins.

    Clinically Important Interactions and Implications of Drug Distribution

    • Drugs may interact by binding to shared plasma protein binding sites.
    • One drug displacing another can change the concentration of the free drug, leading to possible adverse effects in the body.

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    Related Documents

    Drug Distribution PDF

    Description

    Explore the essential concepts of drug distribution in this quiz. Understand how drugs move from the bloodstream to various tissues and learn about the impact of factors like lipid solubility and body water compartments. Test your knowledge on active transport and the different states of drug molecules.

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