USMLE-like pharmacology quiz. Part 3: pharmacokinetics (drug metabolism)

The following are multiple choice questions in a style similar to those included in the USMLE step 1. The main topic here is: pharmacokinetics (drug metabolism). This quiz has been uploaded to Scribd by medical student James Lamberg. The correct answers can be found in link at the end of this post.

Note: the words underlined don’t mean right answer but link to another page.

6 – Pharmacokinetics: Drug Metabolism
1.1) Which of the following locations is the most likely for finding a free, unaltered drug?
a) Urine
b) Feces
c) Breast milk
d) Fat
e) Sweat

1.2) Most drugs are active in their ____ form and inactive in their ____ form.
a) Non-polar; Polar
b) Polar; Non-polar
c) Water-soluble; Lipid-soluble
d) Lipid-insoluble; Water-insoluble
e) Neutral; Neutral
2.1) Drug biotransformation phase I makes drugs ____ polar for metabolism and phase II
makes drugs ____ polar for excretion.
a) More; More
b) More; Less
c) Less; More
d) Less; Less
2.2) Which of the following is NOT a phase II substrate?
a) Glucuronic acid
b) Sulfuric acid
c) Acetic acid
d) Amino acids
e) Alcohol
3) Which of the following reactions is phase II and NOT phase I?
a) Oxidations
b) Reductions
c) Conjugations
d) Deaminations
e) Hydrolyses
4) Which of the following metabolically active tissues is the principle organ for drug
metabolism?
a) Skin
b) Kidneys
c) Lungs
d) Liver
e) GI Tract
5.1) Damage at which of the following locations would most affect the goals of phase II
biotransformation?
a) Skin
b) Kidneys
c) Lungs
d) Liver
e) GI Tract
Match the biotransformation reaction with the drug:
5.2) Hydroxylation of aromatic ring to increase polarity a) Codeine
5.3) N-dealkylation b) Morphine
5.4) Sulfoxidation c) Thioridazine
5.5) O-dealkylation d) Nicotine
5.6) N-oxidation e) Phenobarbitol
5.7) Side chain oxidation with -OH to increase polarity f) Pentobarbitol
5.8) Conversion to glutathione and reactive intermediate g) Acetaminophen
6.1) What is the goal of the P450 system (microsomes pinched off from endoplasmic
reticulum)?
a) Metabolism of substances
b) Detoxification of substances
c) Increasing pH of compartments containing substances
d) Decreasing pH of compartments containing substances
e) A & B
6.2) Regarding the microsomal drug metabolizing system, a patient with late stage
alcoholism and liver damage would have more ETOH available due to which of the
following concepts?
a) Increased induction
b) Decreased induction
c) Increased inhibition
d) Decreased inhibition
6.3) Regarding the microsomal drug metabolizing system, a patient who is a chronic user
of barbiturates would need more drug to produce the same effects due to which of the
following concepts?
a) Increased induction
b) Decreased induction
c) Increased inhibition
d) Decreased inhibition
6.4) Which of the following are the drugs that induce CYP 1A2 and the drugs that have
their metabolism induced by 1A2?
a) Carbamazepine & phenobarbitol; Theophyline & warfarin
b) Phenobarbitol & phenytoin ; Phenytoin & warfarin
c) Carbamazepine & phenytoin; Warfarin
d) Carbamazepine; Cyclosporine
6.5) Which of the following are the drugs that inhibit CYP 1A2 and the drugs that have
their metabolism inhibited by 1A2?
a) SSRIs; Phenytoin & warfarin
b) Amiodarone & cimetidine; Phenytoin & warfarin
c) Cimetidine, erythromycin, & grapefruit juice; Theophyline & warfarin
d) Cimetidine & erythromycin; Cyclosporine
6.6) Which of the following groups of people is the least likely to have biotransformation
effects due to altered hepatic function?

a) Infants

b) Adults

c) Elderly

d) Chronic alcoholics

e) Acetaminophen overdoses

6.7) In what location does amino acid conjugation of glycine (e.g. salicyclic acid) take

place?

a) Microsomal

b) Cytosol

c) Mitochondria

6.8) Where does acetylation conjugation (e.g. isoniazid) and sulfate conjugation (e.g.

acetaminophen) take place?

a) Microsomal

b) Cytosol

c) Mitochondria

6.9) Where does glucuronide conjucation (e.g. digoxin, bilirubin) take place?

a) Microsomal

b) Cytosol

c) Mitochondria

6.10) What is a result of conjugation of isoniazid via N-acetylation?

a) Detoxification of liver

b) Detoxification of kidneys

c) Detoxification of blood

d) Detoxification of urine

e) Hepatotoxicity

7 – Pharmacokinetics: Principles of Eliminations
1.1) One liter contains 1,000 mg of a drug. After one hour, 900 mg of the drug remains.
What is the clearance?
a) 100 mL
b) 100 mL/hr
c) 1 mg/ml
d) 100 mg
e) 1 mg/sec
1.2) To maintain a drug concentration at steady state, the dosing rate should equal the
elimination rate. Which of the following is true? (CL = Drug Clearance)
a) Dosing rate = CL + target concentration
b) Dosing rate = CL – target concentration
c) Dosing rate = CL * target concentration
d) Dosing rate = CL / target concentration
1.3) Which of the following is most useful in determining the rate of elimination of a
drug, in general?
a) Drug concentration in urine (renal elimination)
b) Drug concentration in stool (bilary elimination)
c) Drug concentration in blood
d) Drug concentration in brain
e) Drug oxidation rate
2.1) For first-order drug elimination, half life t(1/2) is ____ at two places on the curve
and a constant ____ is lost per unit time.
a) Equal; Amount
b) Equal; Percentage
c) Not equal; Amount
d) Not equal; Percentage
2.2) For first-order drug elimination, given the half-life equation of t(1/2) = (0.693 * Vd)
/ CL, how many half-lives would be necessary to reach steady state (≈95%) without a
loading dose?
a) 1 to 2
b) 2 to 3
c) 3 to 4
d) 4 to 5
e) 5 to 6
2.3) Which of the following is NOT a drug exhibiting zero-order elimination kinetics?
a) Aspirin
b) Morphine
c) Phenytoin
d) ETOH
2.4) For zero-order drug elimination, half-life t(1/2) is ____ at two places on the curve
and a constant ____ is lost per unit time.
a) Equal; Amount
b) Equal; Percentage
c) Not equal; Amount
d) Not equal; Percentage
2.5) If a drug with a 2-hour half life is given with an initial dose of 8 mcg/ml, assuming
first-order kinetics, how much drug will be left at 6 hours?
a) 8 mcg/ml
b) 4 mcg/ml
c) 2 mcg/ml
d) 1 mcg/ml
e) 0.5 mcg/ml
3.1) What are the units for steady-state concentration (Css), or infusion rate over
clearance?
a) mg/min
b) ml/min
c) mg/ml
d) ml/mg
e) min/mg
3.2) What percentage of the steady-state drug concentration is achieved at 3.3 * t(1/2)?
a) 10%
b) 25%
c) 50%
d) 75%
e) 90%

4.1) Increasing the rate of infusion changes the time necessary to reach the steady-state
concentration.
a) True
b) False
4.2) An injection of two units of a drug once-daily (qd) will yield the same steady-state
concentration as an injection of one unit of a drug twice-daily (bid).
a) True
b) False
5.1) Which of the following drugs would most likely need a loading dose to help reach
therapeutic levels?
a) Acetaminophen, t(1/2) = 2 h
b) Aspirin, t(1/2) = 15 m
c) Tetracycline, t(1/2) = 11 h
d) Digitoxin, t(1/2) = 161 h
e) Adenosine, t(1/2) = 10 s
5.2) A target concentration of 7.5 mg/L of theophylline is required for a 60 kg patient.
What is the loading dose, given the following: Vd = 0.5 L/kg, Cl = 0.04 L/kg/hr, t(1/2) =
9.3 hr?
a) 0.5 L/kg * 60 kg * 7.5 mg/L = 225 mg/h, infusion
b) 0.5 L/kg * 60 kg * 7.5 mg/L = 225 mg, bolus
c) 0.04 L/kg/hr * 60 kg * 7.5 mg/L = 18 mg/h, infusion
d) 0.04 L/kg/hr * 60 kg * 7.5 mg/L = 18 mg, bolus
5.3) A target concentration of 7.5 mg/L of theophylline is required for a 60 kg patient.
What is the steady state maintenance dose, given the following: Vd = 0.5 L/kg, Cl = 0.04
L/kg/hr, t(1/2) = 9.3 hr?
a) 0.5 L/kg * 60 kg * 7.5 mg/L = 225 mg/h, infusion
b) 0.5 L/kg * 60 kg * 7.5 mg/L = 225 mg, bolus
c) 0.04 L/kg/hr * 60 kg * 7.5 mg/L = 18 mg/h, infusion
d) 0.04 L/kg/hr * 60 kg * 7.5 mg/L = 18 mg, bolus

Complete PDF file with answers

More USMLE pharmacology questions

Recommended pharmacokinetics reading

  • Pocket Guide: Pharmacokinetics Made Easy (2009)
  • Basic Clinical Pharmacokinetics (2009)
  • Concepts in Clinical Pharmacokinetics (2010)
  • Clinical Pharmacokinetics, 4th Edition (2008)
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