DAVIS'S DRUG GUIDE FOR NURSES
19TH EDITION
• AUTHOR(S)APRIL HAZARD
VALLERAND; CYNTHIA SANOSKI
TEST BANK
1
Drug Reference
Warfarin — Anticoagulant (Vitamin K antagonist) — Drug
Interactions & Patient/Family Teaching
Clinical stem
A 68-year-old man with atrial fibrillation is admitted after a
minor GI bleed 2 days ago. Current orders: resume warfarin 3
mg PO tonight. Latest labs: INR 1.4 (yesterday); Hgb 10.8 g/dL;
active medications: amiodarone started 3 days ago, TMP-SMX
prophylaxis started 24 hours ago. Which action should the
nurse take?
,A. Administer the ordered warfarin 3 mg now and recheck INR
in 48 hours.
B. Hold warfarin and notify prescriber about potential
interactions with amiodarone and TMP-SMX.
C. Reduce warfarin dose to 1 mg and administer with evening
meal to decrease GI upset.
D. Give warfarin and request vitamin K be ready in case INR
rises.
Correct answer: B
Rationale — Correct (B)
Holding warfarin and informing the prescriber is safest: both
amiodarone and trimethoprim-sulfamethoxazole inhibit
warfarin metabolism and markedly increase bleeding risk. Given
recent GI bleed and INR not therapeutic, restarting without
adjusting for interactions is unsafe. Nursing implication:
communicate medication interactions and recommend
alternative plan (lower dose with monitoring or delay).
Rationale — Incorrect
A. Administering warfarin ignores strong drug–drug interactions
and recent bleed—unsafe.
C. Arbitrarily reducing dose without prescriber input still risks
over-anticoagulation with interacting drugs.
D. Giving warfarin while merely “requesting vitamin K” is
reactive and places patient at avoidable risk; vitamin K is not a
substitute for prevention.
,Teaching point:
Report interacting meds (e.g., TMP-SMX, amiodarone) before
restarting warfarin.
Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Drug Interactions & Patient/Family
Teaching].
2
Drug Reference
Codeine — Opioid analgesic (prodrug) — Pharmacogenomics &
Adverse Reactions
Clinical stem
A 9-year-old girl (weight 30 kg) is prescribed oral codeine for
post-tonsillectomy pain. Her mother reports that a family
member had extreme sleepiness after codeine years ago. Which
is the nurse’s priority action?
A. Administer the first dose and observe for sedation for 30
minutes.
B. Contact the prescriber to recommend an alternative
analgesic due to possible CYP2D6 variability.
C. Educate the mother that codeine is safe in children if dosed
by weight and give as ordered.
D. Ask the mother to withhold codeine and use acetaminophen
only for 48 hours.
, Correct answer: B
Rationale — Correct (B)
Genetic variability in CYP2D6 causes ultra-rapid metabolism of
codeine to morphine (risk: severe respiratory depression) or
poor metabolism with no analgesia. Family history of extreme
sedation suggests possible ultra-rapid metabolizer. For a
pediatric patient after tonsillectomy (higher risk), substituting a
non-codeine analgesic is safest. Notify prescriber to change
therapy.
Rationale — Incorrect
A. Administering without addressing genetic risk may
precipitate life-threatening respiratory depression.
C. Saying codeine is safe ignores pharmacogenomic risk and
known pediatric post-tonsillectomy warnings.
D. Withholding and using only acetaminophen may be
inadequate for severe postoperative pain; the prescriber should
be involved to choose an appropriate alternative.
Teaching point:
Avoid codeine in children post-tonsillectomy if CYP2D6 rapid
metabolism is suspected.
Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Pharmacogenomics & Adverse Reactions].
3
19TH EDITION
• AUTHOR(S)APRIL HAZARD
VALLERAND; CYNTHIA SANOSKI
TEST BANK
1
Drug Reference
Warfarin — Anticoagulant (Vitamin K antagonist) — Drug
Interactions & Patient/Family Teaching
Clinical stem
A 68-year-old man with atrial fibrillation is admitted after a
minor GI bleed 2 days ago. Current orders: resume warfarin 3
mg PO tonight. Latest labs: INR 1.4 (yesterday); Hgb 10.8 g/dL;
active medications: amiodarone started 3 days ago, TMP-SMX
prophylaxis started 24 hours ago. Which action should the
nurse take?
,A. Administer the ordered warfarin 3 mg now and recheck INR
in 48 hours.
B. Hold warfarin and notify prescriber about potential
interactions with amiodarone and TMP-SMX.
C. Reduce warfarin dose to 1 mg and administer with evening
meal to decrease GI upset.
D. Give warfarin and request vitamin K be ready in case INR
rises.
Correct answer: B
Rationale — Correct (B)
Holding warfarin and informing the prescriber is safest: both
amiodarone and trimethoprim-sulfamethoxazole inhibit
warfarin metabolism and markedly increase bleeding risk. Given
recent GI bleed and INR not therapeutic, restarting without
adjusting for interactions is unsafe. Nursing implication:
communicate medication interactions and recommend
alternative plan (lower dose with monitoring or delay).
Rationale — Incorrect
A. Administering warfarin ignores strong drug–drug interactions
and recent bleed—unsafe.
C. Arbitrarily reducing dose without prescriber input still risks
over-anticoagulation with interacting drugs.
D. Giving warfarin while merely “requesting vitamin K” is
reactive and places patient at avoidable risk; vitamin K is not a
substitute for prevention.
,Teaching point:
Report interacting meds (e.g., TMP-SMX, amiodarone) before
restarting warfarin.
Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Drug Interactions & Patient/Family
Teaching].
2
Drug Reference
Codeine — Opioid analgesic (prodrug) — Pharmacogenomics &
Adverse Reactions
Clinical stem
A 9-year-old girl (weight 30 kg) is prescribed oral codeine for
post-tonsillectomy pain. Her mother reports that a family
member had extreme sleepiness after codeine years ago. Which
is the nurse’s priority action?
A. Administer the first dose and observe for sedation for 30
minutes.
B. Contact the prescriber to recommend an alternative
analgesic due to possible CYP2D6 variability.
C. Educate the mother that codeine is safe in children if dosed
by weight and give as ordered.
D. Ask the mother to withhold codeine and use acetaminophen
only for 48 hours.
, Correct answer: B
Rationale — Correct (B)
Genetic variability in CYP2D6 causes ultra-rapid metabolism of
codeine to morphine (risk: severe respiratory depression) or
poor metabolism with no analgesia. Family history of extreme
sedation suggests possible ultra-rapid metabolizer. For a
pediatric patient after tonsillectomy (higher risk), substituting a
non-codeine analgesic is safest. Notify prescriber to change
therapy.
Rationale — Incorrect
A. Administering without addressing genetic risk may
precipitate life-threatening respiratory depression.
C. Saying codeine is safe ignores pharmacogenomic risk and
known pediatric post-tonsillectomy warnings.
D. Withholding and using only acetaminophen may be
inadequate for severe postoperative pain; the prescriber should
be involved to choose an appropriate alternative.
Teaching point:
Avoid codeine in children post-tonsillectomy if CYP2D6 rapid
metabolism is suspected.
Citation:
Vallerand, A. H., & Sanoski, C. (2025). Davis's Drug Guide for
Nurses (19th ed.). [Pharmacogenomics & Adverse Reactions].
3
