Medical Pharmacology: Drug Metabolism Practice Questions
Choose the correct answer for each question.
Drug-drug interactions may account for variation in drug metabolism rate.
True
False
Drug-drug interactions:
May occur when two drugs are coadministered
Typically requires interacting drugs to be metabolized by the same enzyme or enzyme isoform.
Both
Neither
An example of a drug-drug interactions involves an antifungal drug, ketoconazole.
If ketoconazole, metabolized by a cytochrome P450 isoform CYP3A4, is coadministered
with an HIV protease inhibitor, also metabolized by CYP3A4, then which one(s)
of the following consequences may occur?
Competition for CYP3A4 between these enzymes substrates decreases protease inhibitor clearance.
Plasma concentration of protease inhibitors in this setting will increase, potentially inducing toxicity.
Both
Neither
Clinically relevant drug-drug interactions are more likely when the drug exhibits a narrow therapeutic index.
True
False
Drug-drug interactions as a result of cytochrome P450 inducers.
These inducers increase the concentration of cytochrome P450 isoforms.
After enzyme induction, cytochrome P450 enzymes may increase metabolism of many other drugs.
Both
Neither
One example of a cytochrome P450 enzyme inducer is St. John's wort: Administration of St. John's wort increases liver CYP3A4.
True
False
Terfenadine, an antihistamine:
Terfenadine metabolism was inhibited by grapefruit juice, erythromycin, and other CYP3A4 substrates.
Terfenadine,
a prodrug, is activated by CYP3A4 catalyzed oxidation.
Elevated terfenadine levels, as a result of reduced CYP3A4 activity, was associated with serious ventricular tachyarrhythmias.
Secobarbital by alkylating the cytochrome P450 complex mediates essentially irreversible enzyme inhibition.
Ritonovir, classified as a protease inhibitor with efficacy against HIV, is very effective inhibitor of CYP3A4.
Both
Neither
Ketoconazole, the antifungal drug, binds to the heme iron at the active site of cytochrome P450 enzymes. This binding, by competitive inhibition mechanisms,
limits metabolism of other drugs coadministered with ketoconazole.
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Source Material:
Buxton ILO Chapter
2: Pharmcokinetics: The Dynamics of Drug Absorption,
Distribution, Metabolism, and Elimiation in Goodman & Gilman's:
The Pharmacological Basis of Therapeutics, 14e, (Brunton LL H
Knollmann BC, eds) McGraw-Hill Education, 2023.
Gonzalez FJ
Coughtrie M Chapter 5: Drug Metabolism in Goodman & Gilman's:
The Pharmacological Basis of Therapeutics, 14e, (Brunton LL H
Knollmann BC, eds) McGraw-Hill Education, 2023.
Holford NHG Chapter
3: Pharmacokinetics & Pharmacodynamics: Rational Dosing &
the Time Course of Drug Action: in Basic & Clinical
Pharmacology (Katzung BG, Editor; Vanderah TW, Associate
editor) 15e McGraw Hill 2021.
Correia MA Chapter 4
Drug Biotransformation in Basic &
Clinical Pharmacology (Katzung BG, Editor; Vanderah TW, Associate
editor) 15e McGraw Hill 2021.
Baca QJ Golan DE
Pharmacokinetics Chapter 3: Principles of Pharmacology:
The Pathophysiologic Basis of Drug Therapy. (Golan DE, editor-in
chief, Armstrong EJ Armstrong AW, associate editors) 4e Wolters
Kluwer 2017.
Guengerich FP
Chapter 4: Drug Metabolism in
Principles of Pharmacology: The Pathophysiologic Basis of Drug Therapy. (Golan DE, editor-in
chief, Armstrong EJ Armstrong AW, associate editors) 4e Wolters
Kluwer 2017.
Flood P Shafer SL
Chapter 2 Basic Principles of Pharmacology in Stoelting's
Pharmacology & Physiology in Anesthetic Practice (Glood P
Rathmell JP Urman RD, eds) 6e Wolters Kluwer 2022.
Burchum JR Rosenthal
LD Lehne's Pharmacology for Nursing Care Unit II Chapter 4
Pharmcokinetics 11 e Elsevier 2022.
