A drug with a large volume of distribution (Vd) is administered IV. What is the
expected onset and duration?
A) Rapid onset, short duration
B) Slow onset, long duration
C) Rapid onset, long duration
D) Slow onset, short duration
Answer: C
1. Rationale: IV administration bypasses absorption (rapid onset). A large Vd
means the drug distributes widely into tissues, taking a long time to be cleared
(long duration).
A patient is a rapid CYP2C19 metabolizer. They are prescribed clopidogrel. What is
the clinical effect?
A) Decreased conversion to active metabolite, increased risk of stent thrombosis
B) Increased conversion to active metabolite, increased risk of bleeding
C) No effect on drug metabolism
D) Increased risk of toxicity
Answer: B
2. Rationale: Clopidogrel requires CYP2C19 for activation. Rapid metabolizers
create more of the active metabolite, increasing antiplatelet effect and
bleeding risk.
Which of the following best describes an allosteric modulator?
A) Binds to the primary active site and activates the receptor
B) Binds to a separate site, enhancing or inhibiting the primary agonist
C) Binds to the active site and blocks all activation
D) Permanently alters the receptor conformation
Answer: B
, 3. Rationale: Allosteric modulators bind to a site distinct from the orthosteric site,
causing a conformational change that modulates the effect of the endogenous
agonist.
A patient with cirrhosis is prescribed a drug with high first-pass extraction. How will
cirrhosis affect bioavailability?
A) Decreased bioavailability due to portosystemic shunting
B) Increased bioavailability due to decreased hepatic clearance
C) No change in bioavailability
D) Decreased bioavailability due to decreased absorption
Answer: B
4. Rationale: High first-pass extraction drugs are heavily metabolized in the liver.
Cirrhosis causes portosystemic shunting (blood bypasses the liver) and
decreased hepatocyte function, significantly increasing systemic
bioavailability.
Phase II hepatic metabolism (conjugation) typically results in a metabolite that is:
A) More lipid soluble and pharmacologically active
B) More water soluble and readily excreted by the kidneys
C) Highly protein bound
D) Unchanged from the parent drug
Answer: B
5. Rationale: Phase II reactions attach polar molecules to the drug, dramatically
increasing water solubility and allowing renal excretion.
A drug acts as a negative allosteric modulator at the GABA-A receptor. What is the
expected clinical effect?
A) Anxiolysis and sedation
B) Seizure prophylaxis
C) Anxiety and convulsions
D) Muscle relaxation
Answer: C
, 6. Rationale: GABA is the primary inhibitory neurotransmitter. A negative
allosteric modulator decreases GABA's effect, leading to CNS excitation,
anxiety, and seizures.
Which of the following variables affects the calculation of a maintenance dose?
A) Volume of distribution
B) Clearance
C) Bioavailability of loading dose
D) Peak serum concentration
Answer: B
7. Rationale: Maintenance dose = Clearance x Desired steady-state
concentration / Bioavailability. Clearance is the rate of elimination.
P-glycoprotein (P-gp) is located in the renal proximal tubule. Inhibition of P-gp will
cause:
A) Decreased renal clearance of the substrate
B) Increased renal clearance of the substrate
C) No effect on renal clearance
D) Increased hepatic clearance
Answer: A
8. Rationale: In the kidneys, P-gp pumps substrates from tubular cells into the
urine for excretion. Inhibiting P-gp stops this pumping action, decreasing renal
clearance.
A drug demonstrates first-order kinetics. This means:
A) A constant amount of drug is eliminated per hour
B) The elimination rate is proportional to the plasma concentration
C) The drug is metabolized only by Phase I reactions
D) The drug is highly protein bound
Answer: B