NU 641 Exam 1 Practice Questions with 100% Correct
Answers | Verified | Latest Update 2026/2027
1. The time required to reach steady-state concentration of a medication is
approximately:
A) One half-life
B) Two half-lives
C) Four to five half-lives
D) Ten half-lives
Answer C: Four to five half-lives
Rationale: Steady state is achieved after 4-5 half-lives, when drug administration
and elimination are balanced.
2. A patient has been on a medication for 2 weeks. How long does it take to
reach steady state if the drug has a half-life of 24 hours?
A) 2 days
B) 4 days
C) 5 days
D) 10 days
Answer C: 5 days
Rationale: Four to five half-lives = 4-5 days. At steady state, drug levels remain
consistent between doses .
,3. What is the purpose of a loading dose?
A) To maintain therapeutic levels over a long period
B) To rapidly achieve therapeutic drug levels
C) To reduce the risk of adverse effects
D) To eliminate the drug more quickly
Answer B: To rapidly achieve therapeutic drug levels
Rationale: A loading dose rapidly reaches therapeutic levels before steady state is
achieved; used for drugs with long half-lives (e.g., digoxin, amiodarone) .
4. The half-life of a drug primarily determines:
A) The peak concentration
B) The dosing interval
C) The onset of action
D) The bioavailability
Answer B: The dosing interval
Rationale: Half-life determines how often a drug must be given. Short half-life =
frequent dosing; long half-life = once-daily dosing .
5. The therapeutic index (TI) is the ratio of:
A) Effective dose to toxic dose
B) Toxic dose to effective dose (LD50/ED50)
C) Maximum dose to minimum dose
D) Peak to trough
,Answer B: Toxic dose to effective dose (LD50/ED50)
Rationale: TI = LD50/ED50. A narrow TI indicates a small margin of safety,
requiring close monitoring .
6. Which of the following describes drugs with a narrow therapeutic range?
A) They are safe to use without monitoring
B) Their levels should be frequently checked
C) They have a wide margin of safety
D) They are always administered orally
Answer B: Their levels should be frequently checked
Rationale: Narrow therapeutic range drugs require frequent monitoring to
prevent toxicity while maintaining efficacy .
7. Which of the following is a CYP450 enzyme inhibitor?
A) Rifampin
B) Phenytoin
C) Ketoconazole
D) Carbamazepine
Answer C: Ketoconazole
Rationale: CYP450 inhibitors (ketoconazole, erythromycin, grapefruit juice,
amiodarone) increase drug levels and toxicity risk .
, 8. CYP450 enzyme inducers have what effect on co-administered drugs?
A) Increased metabolism, decreased drug levels
B) Decreased metabolism, increased drug levels
C) No effect
D) Increased protein binding
Answer A: Increased metabolism, decreased drug levels
Rationale: Inducers (rifampin, carbamazepine, phenytoin, St. John’s Wort) lower
serum concentrations, potentially reducing therapeutic effect .
9. The primary site of most drug metabolism is the:
A) Kidney
B) Liver cytochrome P450 system
C) Gastrointestinal tract
D) Lungs
Answer B: Liver cytochrome P450 system
Rationale: The CYP450 enzyme system in the liver metabolizes most drugs; main
isoenzymes are CYP1, 2, and 3 .
10. Protein binding affects drug availability because:
A) Only unbound (free) drug is pharmacologically active
B) Protein-bound drug is more active
C) Protein binding increases metabolism
D) Protein binding decreases elimination
Answers | Verified | Latest Update 2026/2027
1. The time required to reach steady-state concentration of a medication is
approximately:
A) One half-life
B) Two half-lives
C) Four to five half-lives
D) Ten half-lives
Answer C: Four to five half-lives
Rationale: Steady state is achieved after 4-5 half-lives, when drug administration
and elimination are balanced.
2. A patient has been on a medication for 2 weeks. How long does it take to
reach steady state if the drug has a half-life of 24 hours?
A) 2 days
B) 4 days
C) 5 days
D) 10 days
Answer C: 5 days
Rationale: Four to five half-lives = 4-5 days. At steady state, drug levels remain
consistent between doses .
,3. What is the purpose of a loading dose?
A) To maintain therapeutic levels over a long period
B) To rapidly achieve therapeutic drug levels
C) To reduce the risk of adverse effects
D) To eliminate the drug more quickly
Answer B: To rapidly achieve therapeutic drug levels
Rationale: A loading dose rapidly reaches therapeutic levels before steady state is
achieved; used for drugs with long half-lives (e.g., digoxin, amiodarone) .
4. The half-life of a drug primarily determines:
A) The peak concentration
B) The dosing interval
C) The onset of action
D) The bioavailability
Answer B: The dosing interval
Rationale: Half-life determines how often a drug must be given. Short half-life =
frequent dosing; long half-life = once-daily dosing .
5. The therapeutic index (TI) is the ratio of:
A) Effective dose to toxic dose
B) Toxic dose to effective dose (LD50/ED50)
C) Maximum dose to minimum dose
D) Peak to trough
,Answer B: Toxic dose to effective dose (LD50/ED50)
Rationale: TI = LD50/ED50. A narrow TI indicates a small margin of safety,
requiring close monitoring .
6. Which of the following describes drugs with a narrow therapeutic range?
A) They are safe to use without monitoring
B) Their levels should be frequently checked
C) They have a wide margin of safety
D) They are always administered orally
Answer B: Their levels should be frequently checked
Rationale: Narrow therapeutic range drugs require frequent monitoring to
prevent toxicity while maintaining efficacy .
7. Which of the following is a CYP450 enzyme inhibitor?
A) Rifampin
B) Phenytoin
C) Ketoconazole
D) Carbamazepine
Answer C: Ketoconazole
Rationale: CYP450 inhibitors (ketoconazole, erythromycin, grapefruit juice,
amiodarone) increase drug levels and toxicity risk .
, 8. CYP450 enzyme inducers have what effect on co-administered drugs?
A) Increased metabolism, decreased drug levels
B) Decreased metabolism, increased drug levels
C) No effect
D) Increased protein binding
Answer A: Increased metabolism, decreased drug levels
Rationale: Inducers (rifampin, carbamazepine, phenytoin, St. John’s Wort) lower
serum concentrations, potentially reducing therapeutic effect .
9. The primary site of most drug metabolism is the:
A) Kidney
B) Liver cytochrome P450 system
C) Gastrointestinal tract
D) Lungs
Answer B: Liver cytochrome P450 system
Rationale: The CYP450 enzyme system in the liver metabolizes most drugs; main
isoenzymes are CYP1, 2, and 3 .
10. Protein binding affects drug availability because:
A) Only unbound (free) drug is pharmacologically active
B) Protein-bound drug is more active
C) Protein binding increases metabolism
D) Protein binding decreases elimination
