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Lipophilicity and Drug Penetration Quiz
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Lipophilicity and Drug Penetration Quiz

Created by
@AthleticAsh

Questions and Answers

What is the Log P value calculated from the following data: [Drug]octanol = 0.8 mg/mL and [Drug]water = 0.2 mg/mL?

  • 1.204
  • 3.000
  • 0.301
  • 0.602 (correct)

    • Log P values greater than 5 are associated with optimal gastrointestinal absorption.

    False

    What is the range of optimal Log P values for gastrointestinal absorption by passive diffusion?

    0 to 3

    Log P values are reported for a drug in the literature might be variable due to __________ variation.

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

    Match the following Log P categories with their descriptions:

    <p>Log P &lt; 0 = Hydrophilic compounds Log P between 0 and 3 = Optimal for gastrointestinal absorption Log P &gt; 5 = Bioaccumulation risks Log P values variable = Due to experimental variation</p> Signup and view all the answers

    What does pKa represent in relation to acids?

    <p>A measure of the strength of an acid (ionizability)</p> Signup and view all the answers

    If the pH is 1 unit higher than the pKa, the drug is 91% ionized.

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

    What happens to the Log D value when a drug becomes ionized?

    <p>It decreases.</p> Signup and view all the answers

    The dissociation constant is expressed as _______.

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

    Match the following terms with their correct definitions:

    <p>pKa = Measure of acid strength Ka = Dissociation constant ionized drug = Lower Log D value (less lipophilic) base = Deprotonation of its conjugate acid</p> Signup and view all the answers

    What does the phrase 'like dissolves like' imply regarding lipophilic molecules?

    <p>Lipophilic molecules can easily dissolve in lipids.</p> Signup and view all the answers

    Very lipophilic compounds may be retained in the cell membrane.

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

    What is the primary method to measure a drug's lipophilicity?

    <p>Shaking the drug with a lipophilic solvent and a hydrophilic solvent.</p> Signup and view all the answers

    The formula for calculating the Partition Coefficient, P, is P = [Drug]octanol / [Drug]_____.

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

    Match the drug properties to their corresponding Log P values:

    <p>High Log P = More lipophilic, dissolves more in octanol Low Log P = More hydrophilic, dissolves more in water Log P = 0 = Balanced solubility between octanol and water Negative Log P = Preferential solubility in water over octanol</p> Signup and view all the answers

    If a drug's Log P value is significantly high, what does this indicate?

    <p>The drug is very lipophilic.</p> Signup and view all the answers

    A low Log P value means that the drug tends to be lipophilic.

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

    What does the distribution of the drug between the lipophilic and hydrophilic solvents indicate?

    <p>It indicates the drug's lipophilicity.</p> Signup and view all the answers

    Which of the following factors influences drug delivery?

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

    Drug absorption predominantly occurs through passive transport mechanisms.

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

    What is the major barrier for orally administered drugs?

    <p>Intestinal epithelium</p> Signup and view all the answers

    Lipophilic substances dissolve well in ______ solvents.

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

    Match the drug characteristics to their descriptions:

    <p>Lipophilic = Dissolves well in lipids/non-polar solvents Hydrophilic = Dissolves well in water/polar solvents Transcellular pathway = Route for drug absorption into cells Log P = Measure of drug partitioning in membranes</p> Signup and view all the answers

    Which pathway is critical for drug molecules to enter systemic circulation after absorption?

    <p>Transcellular pathway</p> Signup and view all the answers

    Hydrophilic substances are poorly absorbed in the lipid-rich environment of cell membranes.

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

    What is the relationship between pH and Log P in drug delivery?

    <p>pH affects the ionization and solubility of drugs, which in turn influences their Log P value.</p> Signup and view all the answers

    What is bioisosterism?

    <p>The replacement of an atom or group of atoms with an alternative that has similar properties</p> Signup and view all the answers

    A carbon-deuterium bond is weaker than a carbon-hydrogen bond.

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

    What advantage does the use of deuterium provide in drug design?

    <p>Slower rate of metabolism and improved pharmacokinetics.</p> Signup and view all the answers

    Bioisosteric replacement can lead to improved ________, safety, and tolerability.

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

    Match the following outcomes with their corresponding effects of bioisosterism:

    <p>Improved pharmacokinetics = Slower rate of metabolism Lower doses = Reduced toxicity through alternative pathways Improved safety = Fewer side effects observed Improved efficacy = Increased therapeutic effects</p> Signup and view all the answers

    Which of the following describes an effect of using deuterium in pharmaceuticals?

    <p>Lower doses needed for effectiveness</p> Signup and view all the answers

    Bioisosterism can lead to the creation of new molecules that have properties similar to the parent compound.

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

    What is one potential biological property that can be enhanced through bioisosteric modification?

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

    Study Notes

    Lipophilicity and Drug Penetration

    • Lipophilic molecules can easily pass through cell membranes due to their solubility in lipid bilayers.
    • Very lipophilic compounds may diffuse through the lipid bilayer and be retained in the cell membrane.

    Measuring Lipophilicity

    • Lipophilicity can be assessed by shaking a drug with an immiscible lipophilic solvent (octanol) and a hydrophilic solvent (water).
    • Concentrations of the drug in each layer are measured to determine the drug's distribution and lipophilicity.
    • A drug entirely in the octanol phase indicates it is highly lipophilic.

    Partition Coefficient and Log P

    • The partition coefficient, P, is calculated as the ratio of drug concentration in octanol to that in water.
    • Log P is expressed as Log10(P); higher values indicate greater lipophilicity, lower values indicate higher hydrophilicity.

    Drug Delivery Mechanisms

    • Factors influencing drug delivery include molecular structure, product formulation, and route of administration.
    • Understanding Log P is crucial for exploring the molecular basis of drug delivery.

    Drug Absorption

    • Oral drug absorption is primarily controlled by the intestinal epithelial cell layer.
    • The transcellular pathway, involving partitioning into and across cell membranes, is essential for drug uptake.
    • Drug transport typically occurs passively, following a concentration gradient, favoring small lipophilic compounds.

    Calculating Log P Example

    • Before shaking: [Drug]octanol = 0 mg/mL, [Drug]water = 1.0 mg/mL.
    • After shaking: [Drug]octanol = 0.8 mg/mL, [Drug]water = 0.2 mg/mL.
    • Partition Coefficient P = 0.8 / 0.2 = 4; Log P = Log10(4) = 0.602.

    Optimal Log P Values

    • Optimal Log P values for gastrointestinal absorption (passive diffusion) range from 0 to 3.
    • Values exceeding 5 indicate potential for bioaccumulation (e.g., PCBs).

    pKa and Drug Ionization

    • Dissociation constant (Ka) is expressed as pKa; it measures the strength of an acid and drug ionizability.
    • pKa influences drug ionization at varying pH; a drug is 91% ionized or unionized if the pH differs by one unit from pKa.

    Bioisosterism

    • Bioisosterism involves replacing an atom or group of atoms with a similar one to create a new compound with similar biological activity.
    • Carbon-deuterium bonds are stronger than carbon-hydrogen bonds, which can lead to improved pharmacokinetics, allowing for lower drug doses and enhanced efficacy.

    Impact of pH on Drug Absorption

    • Ionized drugs generally have lower Log D values (less lipophilic) than their unionized forms, with absorption affected by pH levels.

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    Description

    Test your understanding of lipophilicity and its impact on drug penetration in cellular membranes. This quiz covers the measurement of lipophilicity, partition coefficients, and factors influencing drug delivery mechanisms. Assess your knowledge on how molecular structures affect drug solubility and delivery.

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