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
Clinical stem
A 64-year-old male with nonvalvular atrial fibrillation is started
on warfarin 5 mg nightly. His baseline labs: INR 1.1, CBC normal.
He reports a family history of “bleeding with blood thinners.”
The prescriber ordered a warfarin dose without genotyping.
Which nursing action is best before giving the first dose?
A. Administer the ordered warfarin and obtain a baseline INR in
3 days.
B. Hold warfarin and request CYP2C9/VKORC1 genotyping
results before administration.
,C. Give 2.5 mg (half dose) and obtain INR 2 days after first dose.
D. Administer full dose and teach patient to avoid green leafy
vegetables.
Correct answer: B
Rationale — Correct (B)
Genetic variants (CYP2C9, VKORC1) affect warfarin sensitivity
and bleeding risk; family history of bleeding raises suspicion.
Holding and obtaining genotyping (when available) or
consulting prescriber for safer initial dosing aligns with
pharmacogenomic guidance and reduces early over-
anticoagulation risk.
Rationales — Incorrect
A. Unsafe — giving full dose before assessing genetic risk may
cause over-anticoagulation in sensitive patients.
C. Lowering dose empirically is reasonable, but partial dosing
without prescriber/ genetics is incomplete and still risks
inappropriate anticoagulation.
D. Education about diet is important but does not address
immediate genetic bleeding risk or initial dose safety.
Teaching point:
Consider CYP2C9/VKORC1 status or prescriber guidance before
initial warfarin dosing.
Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Warfarin — Pharmacogenomics].
,2
Drug Reference
Clopidogrel — P2Y12 Platelet Inhibitor — Pharmacogenomics /
Drug Interactions
Clinical stem
A 58-year-old woman post-PCI is prescribed clopidogrel. Her
record shows she’s taking omeprazole daily for GERD. Which
nursing action is most appropriate when preparing teaching and
medication administration?
A. Administer clopidogrel and omeprazole together at the same
time.
B. Advise the patient to stop omeprazole immediately to
improve clopidogrel effect.
C. Educate the patient that omeprazole may reduce clopidogrel
effectiveness and notify prescriber to consider H2 blocker.
D. Substitute clopidogrel with aspirin without consulting
prescriber.
Correct answer: C
Rationale — Correct (C)
Omeprazole (a CYP2C19 inhibitor) reduces clopidogrel
activation, lowering antiplatelet effect. Nursing best practice:
educate patient about interaction, notify prescriber for
alternative acid suppression (e.g., H2 blocker) or alternative
, antiplatelet — collaborative intervention minimizes thrombotic
risk.
Rationales — Incorrect
A. Co-administration without addressing interaction risks
reduced clopidogrel efficacy.
B. Stopping omeprazole unilaterally could cause reflux
complications; prescriber collaboration is required.
D. Substituting medications without prescriber order is beyond
nursing scope and unsafe.
Teaching point:
CYP2C19 inhibitors (omeprazole) can reduce clopidogrel
activation—notify prescriber.
Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Clopidogrel — Drug Interactions /
Pharmacogenomics].
3
Drug Reference
Isotretinoin — Retinoid — Overview of Risk Evaluation and
Mitigation Systems (REMS) / Females of Reproductive Potential
Clinical stem
A 22-year-old female with severe nodulocystic acne has an
isotretinoin prescription. She is sexually active and has irregular
19TH EDITION
• AUTHOR(S)APRIL HAZARD
VALLERAND; CYNTHIA SANOSKI
TEST BANK
1
Drug Reference
Warfarin — Vitamin K Antagonist — Pharmacogenomics
Clinical stem
A 64-year-old male with nonvalvular atrial fibrillation is started
on warfarin 5 mg nightly. His baseline labs: INR 1.1, CBC normal.
He reports a family history of “bleeding with blood thinners.”
The prescriber ordered a warfarin dose without genotyping.
Which nursing action is best before giving the first dose?
A. Administer the ordered warfarin and obtain a baseline INR in
3 days.
B. Hold warfarin and request CYP2C9/VKORC1 genotyping
results before administration.
,C. Give 2.5 mg (half dose) and obtain INR 2 days after first dose.
D. Administer full dose and teach patient to avoid green leafy
vegetables.
Correct answer: B
Rationale — Correct (B)
Genetic variants (CYP2C9, VKORC1) affect warfarin sensitivity
and bleeding risk; family history of bleeding raises suspicion.
Holding and obtaining genotyping (when available) or
consulting prescriber for safer initial dosing aligns with
pharmacogenomic guidance and reduces early over-
anticoagulation risk.
Rationales — Incorrect
A. Unsafe — giving full dose before assessing genetic risk may
cause over-anticoagulation in sensitive patients.
C. Lowering dose empirically is reasonable, but partial dosing
without prescriber/ genetics is incomplete and still risks
inappropriate anticoagulation.
D. Education about diet is important but does not address
immediate genetic bleeding risk or initial dose safety.
Teaching point:
Consider CYP2C9/VKORC1 status or prescriber guidance before
initial warfarin dosing.
Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Warfarin — Pharmacogenomics].
,2
Drug Reference
Clopidogrel — P2Y12 Platelet Inhibitor — Pharmacogenomics /
Drug Interactions
Clinical stem
A 58-year-old woman post-PCI is prescribed clopidogrel. Her
record shows she’s taking omeprazole daily for GERD. Which
nursing action is most appropriate when preparing teaching and
medication administration?
A. Administer clopidogrel and omeprazole together at the same
time.
B. Advise the patient to stop omeprazole immediately to
improve clopidogrel effect.
C. Educate the patient that omeprazole may reduce clopidogrel
effectiveness and notify prescriber to consider H2 blocker.
D. Substitute clopidogrel with aspirin without consulting
prescriber.
Correct answer: C
Rationale — Correct (C)
Omeprazole (a CYP2C19 inhibitor) reduces clopidogrel
activation, lowering antiplatelet effect. Nursing best practice:
educate patient about interaction, notify prescriber for
alternative acid suppression (e.g., H2 blocker) or alternative
, antiplatelet — collaborative intervention minimizes thrombotic
risk.
Rationales — Incorrect
A. Co-administration without addressing interaction risks
reduced clopidogrel efficacy.
B. Stopping omeprazole unilaterally could cause reflux
complications; prescriber collaboration is required.
D. Substituting medications without prescriber order is beyond
nursing scope and unsafe.
Teaching point:
CYP2C19 inhibitors (omeprazole) can reduce clopidogrel
activation—notify prescriber.
Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Clopidogrel — Drug Interactions /
Pharmacogenomics].
3
Drug Reference
Isotretinoin — Retinoid — Overview of Risk Evaluation and
Mitigation Systems (REMS) / Females of Reproductive Potential
Clinical stem
A 22-year-old female with severe nodulocystic acne has an
isotretinoin prescription. She is sexually active and has irregular
