DAVIS'S DRUG GUIDE FOR NURSES
19TH EDITION
• AUTHOR(S)APRIL HAZARD
VALLERAND; CYNTHIA SANOSKI
TEST BANK
1
Drug Reference: Warfarin — Vitamin K Antagonist —
Pharmacogenomics / Special Dosing Considerations
Stem: A 68-year-old man with new atrial fibrillation is started
on warfarin 5 mg PO nightly. His baseline INR is 1.0. He reports
a history of excessive bruising in the past and says a family
member took warfarin and needed very low doses. Which
additional test or action would best guide safe warfarin dosing
for this patient?
A. Start the current dose and recheck INR in 1 week; adjust per
INR.
B. Order CYP2C9 and VKORC1 genotype testing before dose
escalation.
,C. Prescribe vitamin K 2.5 mg daily prophylactically to prevent
over-anticoagulation.
D. Replace warfarin with aspirin because of family history of
sensitivity.
Correct answer: B
Rationales
Correct (B): Genetic variants in CYP2C9 and VKORC1
significantly affect warfarin metabolism and sensitivity. Testing
can explain family sensitivity and guide an initial lower dose,
reducing bleeding risk. This aligns with pharmacogenomic
nursing principles and “Special Dosing Considerations.”
Incorrect (A): While INR monitoring is essential, starting a
standard dose without considering pharmacogenomics and
family history risks early over-anticoagulation. Waiting ignores
evidence that genotype can inform initial dosing.
Incorrect (C): Prophylactic vitamin K could negate
anticoagulation and is not recommended; vitamin K is for
reversal, not prevention.
Incorrect (D): Aspirin is inadequate for stroke prevention in AF
and does not address individual warfarin sensitivity; switching
without indication is inappropriate.
Teaching point: Consider CYP2C9/VKORC1 testing when family
sensitivity or bleeding risk exists.
Citation: Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug
Guide for Nurses (19th ed.). [Warfarin — Pharmacogenomics /
Special Dosing Considerations].
,2
Drug Reference: Clopidogrel — P2Y₁₂ Receptor Inhibitor —
Pharmacogenomics / Drug Interactions
Stem: A 59-year-old woman is admitted for an acute myocardial
infarction and prescribed clopidogrel 75 mg daily after PCI. Her
chart shows she’s been taking omeprazole daily for GERD.
Which action should the nurse take?
A. Leave both medications unchanged; no interaction of
consequence.
B. Hold clopidogrel and call provider to change to prasugrel.
C. Notify the prescriber that omeprazole may reduce
clopidogrel activation (CYP2C19); recommend switching
omeprazole to an H2 blocker.
D. Administer both and add a proton pump inhibitor with meals
to reduce GI bleeding risk.
Correct answer: C
Rationales
Correct (C): Clopidogrel is a prodrug activated by CYP2C19.
Omeprazole (a CYP2C19 inhibitor) can reduce antiplatelet
effect. Nursing best practice is to notify the prescriber and
suggest switching to an H2 blocker or using pantoprazole (less
interaction) to maintain antiplatelet efficacy.
Incorrect (A): Ignoring the interaction risks reduced clopidogrel
efficacy and stent thrombosis—not acceptable.
, Incorrect (B): Holding clopidogrel without prescriber order is
unsafe; changing to prasugrel requires assessment of bleeding
risk and is prescriber decision.
Incorrect (D): Adding another PPI without addressing the
interaction still risks reduced clopidogrel activation;
indiscriminate addition is unsafe.
Teaching point: CYP2C19 inhibitors (omeprazole) can reduce
clopidogrel activation; consider H2 blockers.
Citation: Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug
Guide for Nurses (19th ed.). [Clopidogrel — Pharmacogenomics
/ Drug Interactions].
3
Drug Reference: Codeine — Opioid Analgesic (prodrug) — The
Pediatric Patient / Pharmacogenomics
Stem: A 4-year-old child (weight 18 kg) undergoing
tonsillectomy is prescribed codeine for postoperative pain. The
child’s mother asks about safety because her older child had
“an ultra-fast” reaction to codeine. Which is the best nursing
action?
A. Give codeine as ordered and instruct the parent to report any
unusual sleepiness.
B. Recommend genetic testing or avoid codeine because
CYP2D6 ultra-rapid metabolizers can convert codeine to toxic
morphine levels.
19TH EDITION
• AUTHOR(S)APRIL HAZARD
VALLERAND; CYNTHIA SANOSKI
TEST BANK
1
Drug Reference: Warfarin — Vitamin K Antagonist —
Pharmacogenomics / Special Dosing Considerations
Stem: A 68-year-old man with new atrial fibrillation is started
on warfarin 5 mg PO nightly. His baseline INR is 1.0. He reports
a history of excessive bruising in the past and says a family
member took warfarin and needed very low doses. Which
additional test or action would best guide safe warfarin dosing
for this patient?
A. Start the current dose and recheck INR in 1 week; adjust per
INR.
B. Order CYP2C9 and VKORC1 genotype testing before dose
escalation.
,C. Prescribe vitamin K 2.5 mg daily prophylactically to prevent
over-anticoagulation.
D. Replace warfarin with aspirin because of family history of
sensitivity.
Correct answer: B
Rationales
Correct (B): Genetic variants in CYP2C9 and VKORC1
significantly affect warfarin metabolism and sensitivity. Testing
can explain family sensitivity and guide an initial lower dose,
reducing bleeding risk. This aligns with pharmacogenomic
nursing principles and “Special Dosing Considerations.”
Incorrect (A): While INR monitoring is essential, starting a
standard dose without considering pharmacogenomics and
family history risks early over-anticoagulation. Waiting ignores
evidence that genotype can inform initial dosing.
Incorrect (C): Prophylactic vitamin K could negate
anticoagulation and is not recommended; vitamin K is for
reversal, not prevention.
Incorrect (D): Aspirin is inadequate for stroke prevention in AF
and does not address individual warfarin sensitivity; switching
without indication is inappropriate.
Teaching point: Consider CYP2C9/VKORC1 testing when family
sensitivity or bleeding risk exists.
Citation: Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug
Guide for Nurses (19th ed.). [Warfarin — Pharmacogenomics /
Special Dosing Considerations].
,2
Drug Reference: Clopidogrel — P2Y₁₂ Receptor Inhibitor —
Pharmacogenomics / Drug Interactions
Stem: A 59-year-old woman is admitted for an acute myocardial
infarction and prescribed clopidogrel 75 mg daily after PCI. Her
chart shows she’s been taking omeprazole daily for GERD.
Which action should the nurse take?
A. Leave both medications unchanged; no interaction of
consequence.
B. Hold clopidogrel and call provider to change to prasugrel.
C. Notify the prescriber that omeprazole may reduce
clopidogrel activation (CYP2C19); recommend switching
omeprazole to an H2 blocker.
D. Administer both and add a proton pump inhibitor with meals
to reduce GI bleeding risk.
Correct answer: C
Rationales
Correct (C): Clopidogrel is a prodrug activated by CYP2C19.
Omeprazole (a CYP2C19 inhibitor) can reduce antiplatelet
effect. Nursing best practice is to notify the prescriber and
suggest switching to an H2 blocker or using pantoprazole (less
interaction) to maintain antiplatelet efficacy.
Incorrect (A): Ignoring the interaction risks reduced clopidogrel
efficacy and stent thrombosis—not acceptable.
, Incorrect (B): Holding clopidogrel without prescriber order is
unsafe; changing to prasugrel requires assessment of bleeding
risk and is prescriber decision.
Incorrect (D): Adding another PPI without addressing the
interaction still risks reduced clopidogrel activation;
indiscriminate addition is unsafe.
Teaching point: CYP2C19 inhibitors (omeprazole) can reduce
clopidogrel activation; consider H2 blockers.
Citation: Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug
Guide for Nurses (19th ed.). [Clopidogrel — Pharmacogenomics
/ Drug Interactions].
3
Drug Reference: Codeine — Opioid Analgesic (prodrug) — The
Pediatric Patient / Pharmacogenomics
Stem: A 4-year-old child (weight 18 kg) undergoing
tonsillectomy is prescribed codeine for postoperative pain. The
child’s mother asks about safety because her older child had
“an ultra-fast” reaction to codeine. Which is the best nursing
action?
A. Give codeine as ordered and instruct the parent to report any
unusual sleepiness.
B. Recommend genetic testing or avoid codeine because
CYP2D6 ultra-rapid metabolizers can convert codeine to toxic
morphine levels.
