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;
Detecting and Managing Adverse Drug Reactions
Clinical stem
A 68-year-old man with atrial fibrillation is prescribed warfarin.
On admission his INR is 1.1; his genotype for CYP2C9 shows a
loss-of-function allele and VKORC1 shows increased sensitivity.
Which nursing action is most appropriate when preparing to
start warfarin therapy?
A. Administer the standard initiation dose per protocol and
recheck INR in 3–5 days.
,B. Start a lower-than-standard warfarin initiation dose and plan
earlier INR monitoring (within 24–48 hours).
C. Delay warfarin and substitute low-molecular-weight heparin
indefinitely because of genotype.
D. Start the standard dose and add vitamin K prophylactically to
prevent bleeding.
Correct answer: B
Rationale — Correct (B)
Genetic variants (CYP2C9 loss-of-function, VKORC1 sensitivity)
increase warfarin sensitivity and bleeding risk. Starting at a
lower dose and obtaining earlier INR checks (24–48 hours) is
the safest strategy to titrate therapy and prevent over-
anticoagulation.
Rationale — Incorrect
A. Standard dosing risks rapid INR elevation and bleeding with
these genotypes.
C. LMWH can be used short-term, but indefinite substitution
ignores long-term anticoagulation needs; dose adjustment +
monitoring is preferred.
D. Prophylactic vitamin K would blunt anticoagulant effect and
defeat therapy purpose.
Teaching point:
Genetic variants often require lower initial warfarin doses and
earlier INR checks.
,Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Pharmacogenomics; Detecting and
Managing Adverse Drug Reactions]
2
Drug Reference
Clopidogrel — Antiplatelet (P2Y₁₂ inhibitor) —
Pharmacogenomics; Drug Interactions
Clinical stem
A 56-year-old woman with a recent PCI is prescribed
clopidogrel. Her chart notes she is a CYP2C19 poor metabolizer.
Which nursing implication is the priority?
A. Educate the patient about taking clopidogrel with grapefruit
juice.
B. Notify the prescriber because clopidogrel efficacy may be
reduced; alternative antiplatelet therapy may be required.
C. Increase clopidogrel dose to overcome poor metabolism.
D. Tell the patient to stop clopidogrel immediately and use
aspirin only.
Correct answer: B
Rationale — Correct (B)
CYP2C19 poor metabolizers convert clopidogrel less effectively
to its active metabolite, reducing efficacy and increasing stent
thrombosis risk. Nurse should notify prescriber about genotype
, so an alternative (e.g., prasugrel or ticagrelor) can be
considered.
Rationale — Incorrect
A. Grapefruit juice interacts with CYP3A4, not a remedy for
CYP2C19 poor metabolism.
C. Empiric dose escalation is unsafe and not standard;
alternative agents are preferred.
D. Abruptly stopping dual antiplatelet therapy risks thrombosis;
this decision requires prescriber adjustment.
Teaching point:
CYP2C19 poor metabolizers may need alternative antiplatelet
therapy after PCI.
Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Pharmacogenomics; Drug Interactions]
3
Drug Reference
Isotretinoin — Retinoid — Overview of Risk Evaluation and
Mitigation Systems (REMS); Females of Reproductive Potential
Clinical stem
A 22-year-old woman with severe nodulocystic acne is enrolled
in isotretinoin under iPLEDGE. She asks whether she can stop
using her oral contraceptive now that she has two negative
pregnancy tests. What is the nurse’s best response?
19TH EDITION
• AUTHOR(S)APRIL HAZARD
VALLERAND; CYNTHIA SANOSKI
TEST BANK
1
Drug Reference
Warfarin — Vitamin K Antagonist — Pharmacogenomics;
Detecting and Managing Adverse Drug Reactions
Clinical stem
A 68-year-old man with atrial fibrillation is prescribed warfarin.
On admission his INR is 1.1; his genotype for CYP2C9 shows a
loss-of-function allele and VKORC1 shows increased sensitivity.
Which nursing action is most appropriate when preparing to
start warfarin therapy?
A. Administer the standard initiation dose per protocol and
recheck INR in 3–5 days.
,B. Start a lower-than-standard warfarin initiation dose and plan
earlier INR monitoring (within 24–48 hours).
C. Delay warfarin and substitute low-molecular-weight heparin
indefinitely because of genotype.
D. Start the standard dose and add vitamin K prophylactically to
prevent bleeding.
Correct answer: B
Rationale — Correct (B)
Genetic variants (CYP2C9 loss-of-function, VKORC1 sensitivity)
increase warfarin sensitivity and bleeding risk. Starting at a
lower dose and obtaining earlier INR checks (24–48 hours) is
the safest strategy to titrate therapy and prevent over-
anticoagulation.
Rationale — Incorrect
A. Standard dosing risks rapid INR elevation and bleeding with
these genotypes.
C. LMWH can be used short-term, but indefinite substitution
ignores long-term anticoagulation needs; dose adjustment +
monitoring is preferred.
D. Prophylactic vitamin K would blunt anticoagulant effect and
defeat therapy purpose.
Teaching point:
Genetic variants often require lower initial warfarin doses and
earlier INR checks.
,Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Pharmacogenomics; Detecting and
Managing Adverse Drug Reactions]
2
Drug Reference
Clopidogrel — Antiplatelet (P2Y₁₂ inhibitor) —
Pharmacogenomics; Drug Interactions
Clinical stem
A 56-year-old woman with a recent PCI is prescribed
clopidogrel. Her chart notes she is a CYP2C19 poor metabolizer.
Which nursing implication is the priority?
A. Educate the patient about taking clopidogrel with grapefruit
juice.
B. Notify the prescriber because clopidogrel efficacy may be
reduced; alternative antiplatelet therapy may be required.
C. Increase clopidogrel dose to overcome poor metabolism.
D. Tell the patient to stop clopidogrel immediately and use
aspirin only.
Correct answer: B
Rationale — Correct (B)
CYP2C19 poor metabolizers convert clopidogrel less effectively
to its active metabolite, reducing efficacy and increasing stent
thrombosis risk. Nurse should notify prescriber about genotype
, so an alternative (e.g., prasugrel or ticagrelor) can be
considered.
Rationale — Incorrect
A. Grapefruit juice interacts with CYP3A4, not a remedy for
CYP2C19 poor metabolism.
C. Empiric dose escalation is unsafe and not standard;
alternative agents are preferred.
D. Abruptly stopping dual antiplatelet therapy risks thrombosis;
this decision requires prescriber adjustment.
Teaching point:
CYP2C19 poor metabolizers may need alternative antiplatelet
therapy after PCI.
Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Pharmacogenomics; Drug Interactions]
3
Drug Reference
Isotretinoin — Retinoid — Overview of Risk Evaluation and
Mitigation Systems (REMS); Females of Reproductive Potential
Clinical stem
A 22-year-old woman with severe nodulocystic acne is enrolled
in isotretinoin under iPLEDGE. She asks whether she can stop
using her oral contraceptive now that she has two negative
pregnancy tests. What is the nurse’s best response?
