Question 1

Which of the following best explains why the potassium salt of penicillin V is more water-soluble than the free acid form?

Accepted Answer

The potassium salt dissociates into ions in water, allowing for multiple ion-dipole interactions with water molecules, enhancing solvation and dissolution.

Question 2

A drug molecule contains a carboxylic acid group and is formulated as a sodium salt. Based on the name 'Drug Sodium,' what can you infer about the drug's acid/base character?

Accepted Answer

The drug is acidic because it reacts with sodium hydroxide, a base, to form the salt.

Question 3

Which of the following functional groups would most likely increase the water solubility of a drug molecule?

Accepted Answer

Carboxylic acid

Question 4

A drug is formulated as a lipid-soluble organic salt for intramuscular (IM) depot injection. What is the primary therapeutic advantage of this formulation?

Accepted Answer

It allows for slow, consistent release from the injection site, reducing dosing frequency.

Question 5

Given the following partition coefficient equation: $$P = \frac{[Drug]_{lipid}}{[Drug]_{aqueous}}$$, which statement is correct?

Accepted Answer

A higher P value indicates greater lipid solubility.

Question 6

Which of the following strategies would most likely increase the oral bioavailability of a drug that is poorly absorbed due to low lipid solubility?

Accepted Answer

Convert the drug to a lipid-soluble ester prodrug.

Question 7

A patient is prescribed erythromycin stearate instead of erythromycin free base. What is the main advantage of the stearate salt in oral suspension?

Accepted Answer

It dissolves slowly in the stomach, reducing acid-catalyzed degradation and improving palatability.

Question 8

Which of the following best describes the relationship between lipid solubility and drug action for orally administered drugs, as shown in the parabolic curve?

Accepted Answer

Drug action is maximized at an optimal lipid solubility; too much or too little lipid solubility decreases activity.

Question 9

Which of the following modifications would most likely increase the lipid solubility (log P) of a drug molecule?

Accepted Answer

Replacing a hydroxyl group with a methyl group

Question 10

Why are highly water-soluble drugs like tobramycin often eliminated unchanged in the urine?

Accepted Answer

They are not reabsorbed from the nephron tubule due to their low lipid solubility.

Question 11

Which of the following is a potential risk when mixing an acidic drug (e.g., cefepime) and a basic drug (e.g., gentamicin) in the same IV bag?

Accepted Answer

Formation of an organic salt that is less water-soluble and may precipitate, reducing efficacy and causing harm.

Question 12

A drug is formulated as a hydrochloride salt. What does this indicate about the drug's functional group?

Accepted Answer

The drug contains a basic functional group.

Question 13

Which of the following best explains why amoxicillin has higher oral absorption than ampicillin?

Accepted Answer

Amoxicillin contains a phenol group, increasing water solubility and improving the water/lipid balance for absorption.

Question 14

Which of the following is a therapeutic advantage of enhancing the water solubility of a drug molecule?

Accepted Answer

It allows for the preparation of concentrated IV solutions.

Question 15

Which of the following statements about the metabolism of lipid-soluble drugs is correct?

Accepted Answer

Lipid-soluble drugs often undergo extensive hepatic metabolism before elimination.

Question 16

Which of the following best describes the effect of adding a trifluoromethyl group (CF$$_3) to a $$drug molecule?

Accepted Answer

It increases the drug's lipid solubility.

Question 17

Which of the following is a common strategy to enhance the water solubility of a drug molecule?

Accepted Answer

Formulate the drug as a sodium phosphate or sodium succinate ester.

Question 18

A drug molecule is highly hydrophobic and is not orally absorbed. Which modification would most likely improve its oral absorption?

Accepted Answer

Add a carboxylic acid or hydroxyl group to increase water solubility.

Question 19

Which of the following best explains why some zwitterionic drugs have poor oral absorption?

Accepted Answer

They may have inadequate water solubility, leading to slow dissolution and poor absorption.

Salts and Solubility: Medicinal Chemistry Study Guide

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