Pharmacology Pharmacokinetics and Drug Metabolism 2

Question 1

A drug with a high extraction ratio is administered orally. Which phenomenon most significantly reduces its systemic bioavailability?

Accepted Answer

First-pass metabolism

Answer

Renal elimination

Answer

Enterohepatic recirculation

Answer

Protein binding in plasma

Question 2

Which cytochrome P450 isoform is responsible for metabolizing approximately 50% of all clinically used drugs?

Accepted Answer

CYP3A4

Answer

CYP1A2

Answer

CYP2D6

Answer

CYP2C9

Question 3

A patient taking rifampin begins a new medication. The new drug's plasma levels are unexpectedly low. What is the most likely explanation?

Accepted Answer

Rifampin induces CYP450 enzymes

Answer

Rifampin inhibits renal tubular secretion

Answer

Rifampin competitively binds plasma proteins

Answer

Rifampin increases glomerular filtration rate

Question 4

What is the clinical significance of a drug having a large volume of distribution (Vd)?

Accepted Answer

The drug distributes extensively into tissues

Answer

The drug is predominantly confined to plasma

Answer

The drug is rapidly cleared by the kidneys

Answer

The drug has high oral bioavailability

Question 5

Which phase II metabolic reaction conjugates drugs with glucuronic acid?

Accepted Answer

Glucuronidation

Answer

Acetylation

Answer

Sulfation

Answer

Methylation

Question 6

A drug's half-life is 6 hours. How long does it take to reach approximately 94% of steady-state concentration during continuous infusion?

Accepted Answer

24 hours

Answer

6 hours

Answer

12 hours

Answer

36 hours

Question 7

Which type of pharmacokinetics applies when drug-metabolizing enzymes become saturated, causing a disproportionate increase in plasma concentration with increasing dose?

Accepted Answer

Zero-order kinetics

Answer

First-order kinetics

Answer

Second-order kinetics

Answer

Mixed-order kinetics