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Question 1

Tioconazole is a non polar antifungal agent which is used topically, whereas fluconazole is a polar drug which is used systemically. Which of the following statements is correct?

a) The heterocyclic groups in fluconazole contain more nitrogen atoms making the drug less polar.

b) Increased polarity decreases water solubility.

c) The fluorine substituents in fluconazole increase water solubility.

d) The alcohol group in fluconazole increases polarity.

Question 2

Which of the following strategies will increase the polarity and water solubility of a drug?

a) Removing polar functional groups.

b) Adding extra alkyl groups.

c) Replacing an aromatic ring with a nitrogen containing heterocyclic ring.

d) Replacing an alkyl group with a larger alkyl group.

Question 3

Losartin was developed from structure (I) as an antihypertensive agent by replacing a carboxylic acid group with a tetrazole ring. Which of the following statements is incorrect?

a) The tetrazole ring represents a bio-isostere.

b) The tetrazole ring mimics a carboxylic acid in being planar.

c) The tetrazole ring mimics a carboxylic acid in being acidic.

d) The tetrazole ring is more polar than a carboxylic acid.

Question 4

Why does chlorpropamide have a longer antibiotic activity than tolbutamide?

a) The chloro group of chlorpropamide has an electron-withdrawing effect on the aromatic ring and stabilises the molecule.

b) The methyl group of tolbutamide is susceptible to drug metabolism whereas the chloro substituent of chlorpropamide is not.

c) The urea group of tolbutamide is more susceptible to hydrolysis than the urea group of chlorpropamide.

d) The sulfonamide group of tolbutamide is more susceptible to hydrolysis than the sulfonamide group of chlorpropamide.

Question 5

Lidocaine is a longer lasting local anaesthetic than procaine. Which of the following statements is false?

a) Lidocaine is more stable to hydrolysis.

b) The methyl substituents in lidocaine are important to its stability.

c) The amide group in lidocaine is important to its stability.

d) The NH₂ group in procaine makes procaine less stable than lidocaine.

Question 6

Carbachol is more stable than acetylcholine to hydrolysis. Which of the following statements is not true?

a) The blue coloured methyl group of acetylcholine is susceptible to oxidation by cytochrome P450 enzymes.

b) The blue coloured nitrogen of carbachol stabilises the neighbouring carbonyl group.

c) Carbachol contains a urethane group while acetylcholine contains an ester group.

d) The blue coloured NH₂ group of carbachol is a bio-isostere for the blue coloured CH₃ group of acetylcholine.

Question 7

Some drugs containing an ester group are inactive in vitro, but are active once the drug has been absorbed in vivo. What term is used for such drugs?

a) postdrugs

b) predrugs

c) metabolites

d) prodrugs

Question 8

L791456 is an anti-arthritic drug with a shorter lifetime in the body than L787257. The only difference in the structures is a methyl substituent on one of the pyridine rings. Why does the presence of a methyl group decrease the lifetime of the drug?

a) It increases the basicity of the pyridine ring causing it to bind to plasma proteins.

b) It acts as a steric shield and hinders the drug binding to its target.

c) It is metabolised by oxidative enzymes to an alcohol or carboxylic acid. The resulting polar metabolites are rapidly excreted.

d) It increases the rate of N-oxidation and deactivation of the drug.

Question 9

In Parkinson's disease, there is a lack of the neurotransmitter dopamine in the brain. Adding dopamine itself is not very effective for a variety of reasons. Which of the following statements is not a valid explanation?

a) Dopamine is too polar to cross the blood-brain barrier.

b) Dopamine is chemically unstable.

c) Dopamine is metabolised to inactive metabolites.

d) Dopamine shows no selectivity between dopamine receptors in the brain and peripheral dopamine receptors.

Question 10

Esters are frequently used as prodrugs. Which of the following statements is false?

a) Ester prodrugs are more easily absorbed from the gut than the parent drug if the parent drug is highly polar.

b) Esters are more susceptible to hydrolysis if the alcohol moiety has an electron donating group.

c) Esters can be used to mask a polar alcohol, phenol or carboxylic acid group.

d) It is preferable if the leaving group from ester hydrolysis is a natural chemical such as an amino acid.

Question 11

Fluphenazine decanoate is an ester prodrug for the antipsychotic drug fluphenazine, and is administered by intramuscular injection. Which of the following statements is true?

a) Hydrolysis of the ester reveals a carboxylic acid group on fluphenazine.

b) The ester is hydrophobic which means that it is taken up in fat tissue. As a result, it can only enter the blood supply at a slow rate.

c) The ester is hydrophilic and rapidly enters the blood supply.

d) The ester is rapidly hydrolysed in blood since the pH of blood is slightly alkaline.

Question 12

Structures (I) and (II) are prodrugs of the antibiotic chloramphenicol.

Which of the following statements is true?

a) Structure I is more water soluble than chloramphenicol.

b) Structure II is more water soluble than chloramphenicol.

c) Structure I is used to achieve higher concentrations for injections.

d) Structure II is used to reduce the bitter taste of chloramphenicol.

Question 13

Which of the following statements is true with respect to phosphate prodrugs?

a) Phosphate esters are more polar in nature than the parent drug.

b) Phosphate esters are less water soluble than the parent drug.

c) Phosphate esters are more likely to cross cell membranes than the parent drug.

d) Phosphate esters are resistant to drug metabolism.

Question 14

Candoxatril is an ester prodrug for candoxatrilat which inhibits protease enzymes. Which of the following statements is incorrect?

a) Hydrolysis of the ester reveals a carboxylic acid group on candoxatrilat.

b) The parent drug can be administered orally, whereas the ester prodrug cannot.

c) The bicyclic leaving group is non toxic.

d) The bicyclic system is electron withdrawing and speeds up the rate of ester hydrolysis.

Question 15

Some peptides and proteins have been used as drugs. Which of the following statements is untrue?

a) Protein drugs suffer a disadvantage in that they could produce an immune response.

b) Peptides and proteins generally show poor bioavailability.

c) Peptide drugs are susceptible to peptidase enzymes.

d) Peptide drugs are susceptible to metabolic enzymes but not to digestive enzymes.

Oxford University Press, Online Resource Centre, Chapter 14.

Chapter 14

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