Drug Metabolism

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Questions and Answers

What is one of the factors that could cause significant changes in biological activity of a drug?

  • Smell of the drug
  • Color of the drug
  • 3D shape of the molecule (correct)
  • Size of the drug particles

How was the initial receptor model based on the interaction between drugs and receptors?

  • Lock-and-key concept (correct)
  • Maze concept
  • Jigsaw puzzle concept
  • Musical chairs concept

What can happen when a drug docks with a receptor based on the text?

  • The receptor remains rigid
  • The drug undergoes adjustment
  • The receptor undergoes an adjustment in 3D structure (correct)
  • The receptor loses its 3D structure

How is the drug-receptor association depicted in the text?

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

What is the significance of the first-pass effect mentioned in the text?

<p>It decreases the bioavailability of drugs administered orally. (A)</p> Signup and view all the answers

Why is lidocaine impractical to administer orally?

<p>Over 60% of it is metabolized during its first pass through the liver. (A)</p> Signup and view all the answers

How does the rapid metabolism of lidocaine benefit patients with cardiac arrhythmias?

<p>It decreases toxic responses by converting lidocaine into inactive metabolites. (A)</p> Signup and view all the answers

What development was inspired by the understanding of the metabolic labile site on lidocaine?

<p>Development of primary amine analog tocainide. (C)</p> Signup and view all the answers

What does the pKa measure?

<p>Extent to which the acid reacts with water (B)</p> Signup and view all the answers

Where does the equilibrium lie for a strong acid in water?

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

What does a high pKa value indicate about a weak acid in water?

<p>Lies to the left in equilibrium (A)</p> Signup and view all the answers

What does a pKa for a base actually represent?

<p>The pKa of the conjugate acid of the base (C)</p> Signup and view all the answers

What is the relationship between pH and percent ionization of an HA acid when the pH is 1 unit greater than the pKa?

<p>99% ionized (B)</p> Signup and view all the answers

How does an increase of 2 pH units affect the ionization of a BH+ acid?

<p>99% nonionized (D)</p> Signup and view all the answers

What is the impact of increasing the hydrogen ion concentration on drug equilibrium?

<p>Increases the conjugate base concentration (A)</p> Signup and view all the answers

At what pH value would an HA acid be 50% ionized?

<p>pKa + 1 (A)</p> Signup and view all the answers

Why is it impractical to administer lidocaine orally?

<p>It undergoes rapid metabolism in the liver during the first pass effect. (A)</p> Signup and view all the answers

What happens to lidocaine when administered intravenously for cardiac arrhythmias?

<p>It is rapidly biotransformed to inactive metabolites. (D)</p> Signup and view all the answers

What is a significant characteristic of lidocaine's first-pass effect?

<p>Over 60% of it is metabolized during its initial passage through the liver. (B)</p> Signup and view all the answers

What led to the development of tocainide according to the text?

<p>Understanding the metabolic labile site on lidocaine. (C)</p> Signup and view all the answers

Which factor contributes to the drug-receptor interaction process by favoring the desired pharmacological response?

<p>Good ability of the drug to fit the receptor (C)</p> Signup and view all the answers

Why are second-generation antihistamines like fexofenadine claimed to cause less sedation?

<p>They do not readily penetrate the blood-brain barrier (C)</p> Signup and view all the answers

What happens when a drug binds poorly to a receptor according to the text?

<p>Reverse reaction and reduced pharmacological effect (B)</p> Signup and view all the answers

Why do nonsteroidal anti-inflammatory drugs sometimes cause discomfort and ulceration in the gastrointestinal mucosa?

<p>They combine with undesired cyclooxygenase receptors in the gastrointestinal mucosa (A)</p> Signup and view all the answers

What is the primary amine form of the carboxylic acid at physiological pH?

<p>50% protonated and 50% in the free amine form (D)</p> Signup and view all the answers

Why is adjusting the pH of phenytoin injection to 12 necessary?

<p>To achieve complete ionization (D)</p> Signup and view all the answers

What percentage of the drug is in the ionized form at pH 12?

<p>99.98% (C)</p> Signup and view all the answers

Why is an alkaline solution with a pH of 12 generally not administered with other intravenous fluids?

<p>It can cause patient irritation (B)</p> Signup and view all the answers

What is the importance of understanding the 3D shape of a drug molecule, according to the text?

<p>It can lead to significant changes in the drug's biological activity. (A)</p> Signup and view all the answers

Why is the lock-and-key concept of drug-receptor interaction considered outdated?

<p>It doesn't account for the flexibility of both the drug and receptor. (A)</p> Signup and view all the answers

What effect can drug-receptor association have on macromolecules, as mentioned in the text?

<p>It may alter the configuration of macromolecules for agonist responses. (D)</p> Signup and view all the answers

Why are slight structural variations in drugs significant, according to the text?

<p>They may increase or decrease the drug's biological activity. (B)</p> Signup and view all the answers

Acids are defined as proton acceptors and bases are defined as proton donors.

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

Water can act as an acid by donating a proton to a basic drug.

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

Ionized acids, like carboxylic acids, donate their protons forming ionized conjugate acids.

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

A drug's acid–base properties do not influence its biodistribution and partitioning characteristics.

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

During the initial trip through the liver, a significant proportion of a drug will be transported to the kidneys for excretion.

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

Lidocaine is an example of a drug that undergoes rapid metabolism during the first-pass effect.

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

The first-pass effect of lidocaine makes it practical to administer orally.

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

The understanding of the metabolic labile site on lidocaine led to the development of a similar drug called lidocainide.

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

Phenytoin injection must be adjusted to pH 10 to ensure complete ionization and maximize water solubility.

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

At pH 12, 99.0% of the drug phenytoin will be in the insoluble acid form.

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

A highly alkaline solution with a pH of 12 can be easily administered with other intravenous fluids buffered at pH 7.4.

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

Lowering the pH of phenytoin solution would result in the parent unionized phenytoin precipitating out of solution.

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

An increase of 1 pH unit from the pKa value will cause a BH+ acid to be 90.9% in the ionized form.

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

In the Henderson-Hasselbalch equation, when log [conjugate base] / [acid] = 1, the pH is equal to pKa.

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

Increasing the hydrogen ion concentration (decreasing the pH) will shift the equilibrium to the right for both HA acids and BH+ acids.

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

An increase of 2 pH units essentially shifts an HA acid to complete ionization (99%) and a BH+ acid to the nonionic conjugate base form (0.99%).

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

Why is Tropicamide buffered near pH 4 for eye drop administration?

<p>To maximize water solubility (C)</p> Signup and view all the answers

Why are local anesthetic eye drops sometimes used along with Tropicamide eye drops?

<p>To minimize patient discomfort (A)</p> Signup and view all the answers

In what pH range is indomethacin stabilized to prevent instability issues?

<p>pH 4-5 (C)</p> Signup and view all the answers

Why is only 50% of indomethacin in the water-soluble form when administered as a suspension at pH 4-5?

<p>Due to its proximity to the drug's pKa (C)</p> Signup and view all the answers

Why is the intravenous dosage form of indomethacin prepared as a sodium salt?

<p>To increase water solubility (A)</p> Signup and view all the answers

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