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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?
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.
Log P values greater than 5 are associated with optimal gastrointestinal absorption.
False (B)
What is the range of optimal Log P values for gastrointestinal absorption by passive diffusion?
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.
Log P values are reported for a drug in the literature might be variable due to __________ variation.
Match the following Log P categories with their descriptions:
Match the following Log P categories with their descriptions:
What does pKa represent in relation to acids?
What does pKa represent in relation to acids?
If the pH is 1 unit higher than the pKa, the drug is 91% ionized.
If the pH is 1 unit higher than the pKa, the drug is 91% ionized.
What happens to the Log D value when a drug becomes ionized?
What happens to the Log D value when a drug becomes ionized?
The dissociation constant is expressed as _______.
The dissociation constant is expressed as _______.
Match the following terms with their correct definitions:
Match the following terms with their correct definitions:
What does the phrase 'like dissolves like' imply regarding lipophilic molecules?
What does the phrase 'like dissolves like' imply regarding lipophilic molecules?
Very lipophilic compounds may be retained in the cell membrane.
Very lipophilic compounds may be retained in the cell membrane.
What is the primary method to measure a drug's lipophilicity?
What is the primary method to measure a drug's lipophilicity?
The formula for calculating the Partition Coefficient, P, is P = [Drug]octanol / [Drug]_____.
The formula for calculating the Partition Coefficient, P, is P = [Drug]octanol / [Drug]_____.
Match the drug properties to their corresponding Log P values:
Match the drug properties to their corresponding Log P values:
If a drug's Log P value is significantly high, what does this indicate?
If a drug's Log P value is significantly high, what does this indicate?
A low Log P value means that the drug tends to be lipophilic.
A low Log P value means that the drug tends to be lipophilic.
What does the distribution of the drug between the lipophilic and hydrophilic solvents indicate?
What does the distribution of the drug between the lipophilic and hydrophilic solvents indicate?
Which of the following factors influences drug delivery?
Which of the following factors influences drug delivery?
Drug absorption predominantly occurs through passive transport mechanisms.
Drug absorption predominantly occurs through passive transport mechanisms.
What is the major barrier for orally administered drugs?
What is the major barrier for orally administered drugs?
Lipophilic substances dissolve well in ______ solvents.
Lipophilic substances dissolve well in ______ solvents.
Match the drug characteristics to their descriptions:
Match the drug characteristics to their descriptions:
Which pathway is critical for drug molecules to enter systemic circulation after absorption?
Which pathway is critical for drug molecules to enter systemic circulation after absorption?
Hydrophilic substances are poorly absorbed in the lipid-rich environment of cell membranes.
Hydrophilic substances are poorly absorbed in the lipid-rich environment of cell membranes.
What is the relationship between pH and Log P in drug delivery?
What is the relationship between pH and Log P in drug delivery?
What is bioisosterism?
What is bioisosterism?
A carbon-deuterium bond is weaker than a carbon-hydrogen bond.
A carbon-deuterium bond is weaker than a carbon-hydrogen bond.
What advantage does the use of deuterium provide in drug design?
What advantage does the use of deuterium provide in drug design?
Bioisosteric replacement can lead to improved ________, safety, and tolerability.
Bioisosteric replacement can lead to improved ________, safety, and tolerability.
Match the following outcomes with their corresponding effects of bioisosterism:
Match the following outcomes with their corresponding effects of bioisosterism:
Which of the following describes an effect of using deuterium in pharmaceuticals?
Which of the following describes an effect of using deuterium in pharmaceuticals?
Bioisosterism can lead to the creation of new molecules that have properties similar to the parent compound.
Bioisosterism can lead to the creation of new molecules that have properties similar to the parent compound.
What is one potential biological property that can be enhanced through bioisosteric modification?
What is one potential biological property that can be enhanced through bioisosteric modification?
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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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