PHARMD / DRUG INTERACTIONS / 2026-2027
PharmD Drug Interactions
2026–2027 Medication Safety | Clinical Practice Examination
110 ORIGINAL MULTIPLE-CHOICE QUESTIONS
Pharmacokinetic and pharmacodynamic interactions • clinical judgment • monitoring • patient
counseling
Purpose and appropriate use
An independently authored PharmD-level study resource featuring hypothetical clinical scenarios. It is not an official
PharmD, board, licensing, university, or proprietary examination. Drug-interaction severity, dose adjustments, and
recommended responses can depend on the formulation, indication, dose, kidney or liver function, and current
prescribing information.
Instructions
For each clinical scenario, select the SINGLE BEST answer (A–D). Then review the correct answer, the mechanism-
based rationale, and the incorrect-option analysis. The answers appear immediately below each question for
independent study; cover them while practicing under timed conditions.
Suggested timing: 110–135 minutes. High-risk patient cases should be interpreted as educational examples, never as
instructions to alter actual medications without clinician review.
Content map
01 CYP Inhibition & Toxicity · Questions 1–10
02 Enzyme Induction & Reduced Efficacy · Questions 11–20
03 Anticoagulants & Bleeding · Questions 21–30
04 Serotonin, Sedatives & Neurotoxicity · Questions 31–40
05 Cardiac Rhythm, Potassium & Kidney Injury · Questions 41–50
06 Absorption, Chelation & GI Effects · Questions 51–60
07 Diabetes & Endocrine Safety · Questions 61–70
08 Immunosuppression, Oncology & Gout · Questions 71–80
09 Respiratory Therapy & Inhaled Medications · Questions 81–90
10 Antiepileptics, CNS & Substance-Use Care · Questions 91–100
11 Applied Medication-Safety Decisions · Questions 101–110
Clinical safety reminders
Interaction checking does not replace medication reconciliation and patient assessment. Always identify the full
product and route, establish timing, screen OTC medicines and supplements, evaluate renal/hepatic function,
distinguish pharmacokinetic from pharmacodynamic risks, and consult the up-to-date product label for
contraindications and monitoring requirements.
INDEPENDENT PRACTICE RESOURCE • Page 1
, PHARMD / DRUG INTERACTIONS / 2026-2027
SECTION 01 · CYP Inhibition & Toxicity
10 scenario-based questions | single best answer
001. A patient taking simvastatin 40 mg nightly is prescribed clarithromycin for pneumonia. Which is
the principal drug-interaction concern?
A. Inactivation of simvastatin through chelation
B. Reduced simvastatin absorption and LDL rebound
C. Marked statin exposure and rhabdomyolysis risk
D. Reduced antibiotic exposure from enzyme induction
CORRECT ANSWER: C — Marked statin exposure and rhabdomyolysis risk
Rationale: Clarithromycin strongly inhibits CYP3A4; coadministration with simvastatin is contraindicated.
Select an alternative antibiotic or suspend/change the statin under prescriber direction.
Why the other options are incorrect:
A. This proposed binding or chelation explanation does not describe the important interaction in this case.
B. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
D. The proposed increase in metabolic clearance is not the primary documented effect of this combination.
002. A kidney-transplant recipient stabilized on tacrolimus starts oral voriconazole. What change is
most likely?
A. Voriconazole blocks tacrolimus absorption through gastric pH elevation
B. Tacrolimus exposure increases substantially, requiring planned dose adjustment and level monitoring
C. The drugs form an insoluble intestinal complex
D. Tacrolimus levels fall because voriconazole induces CYP3A
CORRECT ANSWER: B — Tacrolimus exposure increases substantially, requiring planned dose adjustment and
level monitoring
Rationale: Voriconazole inhibits CYP3A metabolism of tacrolimus, potentially producing nephrotoxicity and
neurotoxicity; coordinate preemptive dose adjustment and trough checks.
Why the other options are incorrect:
A. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
C. This proposed binding or chelation explanation does not describe the important interaction in this case.
D. The proposed increase in metabolic clearance is not the primary documented effect of this combination.
003. A patient taking tizanidine for muscle spasm receives fluvoxamine. What should the pharmacist
identify?
A. A contraindicated combination causing excessive hypotension and sedation
B. Loss of tizanidine benefit from accelerated metabolism
C. Increased renal clearance of fluvoxamine
D. Reduced tizanidine effect due to poor gastrointestinal absorption
CORRECT ANSWER: A — A contraindicated combination causing excessive hypotension and sedation
Rationale: Fluvoxamine potently inhibits CYP1A2, sharply increasing tizanidine exposure; profound
hypotension and drowsiness can occur.
Why the other options are incorrect:
B. The proposed increase in metabolic clearance is not the primary documented effect of this combination.
INDEPENDENT PRACTICE RESOURCE • Page 2
, PHARMD / DRUG INTERACTIONS / 2026-2027
C. This renal explanation does not match the key toxicity or exposure change in this scenario.
D. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
004. A patient on tizanidine is prescribed ciprofloxacin for a urinary infection. What is the best safety
interpretation?
A. Avoid the contraindicated pair because tizanidine concentrations can rise dangerously
B. Separate administration by two hours to eliminate the interaction
C. Add a proton pump inhibitor to protect against the interaction
D. Increase tizanidine because ciprofloxacin lowers its exposure
CORRECT ANSWER: A — Avoid the contraindicated pair because tizanidine concentrations can rise
dangerously
Rationale: Ciprofloxacin inhibits CYP1A2, increasing tizanidine exposure and risk of severe hypotension,
bradycardia, and sedation; timing changes do not solve it.
Why the other options are incorrect:
B. Dose spacing cannot reliably remove this interaction when the mechanism persists systemically or is not a timing
effect.
C. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
D. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
005. A stable warfarin patient is prescribed fluconazole. Which monitoring change is most appropriate?
A. Stop INR monitoring because fluconazole prevents warfarin absorption
B. Expect INR to decrease as CYP2C9 activity increases
C. Give vitamin K to every patient automatically before the first dose
D. Arrange closer INR monitoring due to possible increased anticoagulation
CORRECT ANSWER: D — Arrange closer INR monitoring due to possible increased anticoagulation
Rationale: Fluconazole inhibits warfarin metabolism, notably CYP2C9; anticoagulant effect and bleeding risk
can increase, making closer INR surveillance and individualized adjustment appropriate.
Why the other options are incorrect:
A. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
B. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
C. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
INDEPENDENT PRACTICE RESOURCE • Page 3
, PHARMD / DRUG INTERACTIONS / 2026-2027
006. A patient taking metoprolol starts paroxetine. Which observation most suggests an interaction?
A. New bradycardia and dizziness from increased metoprolol exposure
B. Reduced paroxetine absorption caused by metoprolol
C. Persistent hypertension from beta-blocker receptor stimulation
D. Faster heart rate from reduced beta-blocker concentration
CORRECT ANSWER: A — New bradycardia and dizziness from increased metoprolol exposure
Rationale: Paroxetine is a strong CYP2D6 inhibitor and can raise metoprolol concentrations, increasing beta
blockade and causing symptomatic bradycardia or hypotension.
Why the other options are incorrect:
B. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
C. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
D. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
007. A patient taking clopidogrel after coronary stenting begins over-the-counter omeprazole. Which
concern should be reviewed?
A. Enhanced clopidogrel activation and spontaneous bleeding
B. Reduced formation of clopidogrel active metabolite
C. Irreversible blockade of aspirin absorption
D. Increased gastric acidity directly degrading clopidogrel
CORRECT ANSWER: B — Reduced formation of clopidogrel active metabolite
Rationale: Omeprazole inhibits CYP2C19, which is important for clopidogrel activation; consider a less
interacting acid suppressant and follow current product recommendations.
Why the other options are incorrect:
A. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
C. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
D. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
008. A hospitalized patient receiving oral midazolam is started on ritonavir-containing treatment. What
is the key issue?
A. Ritonavir chelation by oral midazolam
B. Complete loss of benzodiazepine receptor binding
C. Midazolam loss of effect through CYP3A induction
D. Markedly increased oral midazolam exposure and prolonged sedation
CORRECT ANSWER: D — Markedly increased oral midazolam exposure and prolonged sedation
Rationale: Ritonavir strongly inhibits CYP3A; oral midazolam coadministration can cause dangerous sedation
and respiratory depression and is generally contraindicated.
Why the other options are incorrect:
A. This proposed binding or chelation explanation does not describe the important interaction in this case.
B. This proposed binding or chelation explanation does not describe the important interaction in this case.
C. The proposed increase in metabolic clearance is not the primary documented effect of this combination.
INDEPENDENT PRACTICE RESOURCE • Page 4
PharmD Drug Interactions
2026–2027 Medication Safety | Clinical Practice Examination
110 ORIGINAL MULTIPLE-CHOICE QUESTIONS
Pharmacokinetic and pharmacodynamic interactions • clinical judgment • monitoring • patient
counseling
Purpose and appropriate use
An independently authored PharmD-level study resource featuring hypothetical clinical scenarios. It is not an official
PharmD, board, licensing, university, or proprietary examination. Drug-interaction severity, dose adjustments, and
recommended responses can depend on the formulation, indication, dose, kidney or liver function, and current
prescribing information.
Instructions
For each clinical scenario, select the SINGLE BEST answer (A–D). Then review the correct answer, the mechanism-
based rationale, and the incorrect-option analysis. The answers appear immediately below each question for
independent study; cover them while practicing under timed conditions.
Suggested timing: 110–135 minutes. High-risk patient cases should be interpreted as educational examples, never as
instructions to alter actual medications without clinician review.
Content map
01 CYP Inhibition & Toxicity · Questions 1–10
02 Enzyme Induction & Reduced Efficacy · Questions 11–20
03 Anticoagulants & Bleeding · Questions 21–30
04 Serotonin, Sedatives & Neurotoxicity · Questions 31–40
05 Cardiac Rhythm, Potassium & Kidney Injury · Questions 41–50
06 Absorption, Chelation & GI Effects · Questions 51–60
07 Diabetes & Endocrine Safety · Questions 61–70
08 Immunosuppression, Oncology & Gout · Questions 71–80
09 Respiratory Therapy & Inhaled Medications · Questions 81–90
10 Antiepileptics, CNS & Substance-Use Care · Questions 91–100
11 Applied Medication-Safety Decisions · Questions 101–110
Clinical safety reminders
Interaction checking does not replace medication reconciliation and patient assessment. Always identify the full
product and route, establish timing, screen OTC medicines and supplements, evaluate renal/hepatic function,
distinguish pharmacokinetic from pharmacodynamic risks, and consult the up-to-date product label for
contraindications and monitoring requirements.
INDEPENDENT PRACTICE RESOURCE • Page 1
, PHARMD / DRUG INTERACTIONS / 2026-2027
SECTION 01 · CYP Inhibition & Toxicity
10 scenario-based questions | single best answer
001. A patient taking simvastatin 40 mg nightly is prescribed clarithromycin for pneumonia. Which is
the principal drug-interaction concern?
A. Inactivation of simvastatin through chelation
B. Reduced simvastatin absorption and LDL rebound
C. Marked statin exposure and rhabdomyolysis risk
D. Reduced antibiotic exposure from enzyme induction
CORRECT ANSWER: C — Marked statin exposure and rhabdomyolysis risk
Rationale: Clarithromycin strongly inhibits CYP3A4; coadministration with simvastatin is contraindicated.
Select an alternative antibiotic or suspend/change the statin under prescriber direction.
Why the other options are incorrect:
A. This proposed binding or chelation explanation does not describe the important interaction in this case.
B. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
D. The proposed increase in metabolic clearance is not the primary documented effect of this combination.
002. A kidney-transplant recipient stabilized on tacrolimus starts oral voriconazole. What change is
most likely?
A. Voriconazole blocks tacrolimus absorption through gastric pH elevation
B. Tacrolimus exposure increases substantially, requiring planned dose adjustment and level monitoring
C. The drugs form an insoluble intestinal complex
D. Tacrolimus levels fall because voriconazole induces CYP3A
CORRECT ANSWER: B — Tacrolimus exposure increases substantially, requiring planned dose adjustment and
level monitoring
Rationale: Voriconazole inhibits CYP3A metabolism of tacrolimus, potentially producing nephrotoxicity and
neurotoxicity; coordinate preemptive dose adjustment and trough checks.
Why the other options are incorrect:
A. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
C. This proposed binding or chelation explanation does not describe the important interaction in this case.
D. The proposed increase in metabolic clearance is not the primary documented effect of this combination.
003. A patient taking tizanidine for muscle spasm receives fluvoxamine. What should the pharmacist
identify?
A. A contraindicated combination causing excessive hypotension and sedation
B. Loss of tizanidine benefit from accelerated metabolism
C. Increased renal clearance of fluvoxamine
D. Reduced tizanidine effect due to poor gastrointestinal absorption
CORRECT ANSWER: A — A contraindicated combination causing excessive hypotension and sedation
Rationale: Fluvoxamine potently inhibits CYP1A2, sharply increasing tizanidine exposure; profound
hypotension and drowsiness can occur.
Why the other options are incorrect:
B. The proposed increase in metabolic clearance is not the primary documented effect of this combination.
INDEPENDENT PRACTICE RESOURCE • Page 2
, PHARMD / DRUG INTERACTIONS / 2026-2027
C. This renal explanation does not match the key toxicity or exposure change in this scenario.
D. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
004. A patient on tizanidine is prescribed ciprofloxacin for a urinary infection. What is the best safety
interpretation?
A. Avoid the contraindicated pair because tizanidine concentrations can rise dangerously
B. Separate administration by two hours to eliminate the interaction
C. Add a proton pump inhibitor to protect against the interaction
D. Increase tizanidine because ciprofloxacin lowers its exposure
CORRECT ANSWER: A — Avoid the contraindicated pair because tizanidine concentrations can rise
dangerously
Rationale: Ciprofloxacin inhibits CYP1A2, increasing tizanidine exposure and risk of severe hypotension,
bradycardia, and sedation; timing changes do not solve it.
Why the other options are incorrect:
B. Dose spacing cannot reliably remove this interaction when the mechanism persists systemically or is not a timing
effect.
C. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
D. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
005. A stable warfarin patient is prescribed fluconazole. Which monitoring change is most appropriate?
A. Stop INR monitoring because fluconazole prevents warfarin absorption
B. Expect INR to decrease as CYP2C9 activity increases
C. Give vitamin K to every patient automatically before the first dose
D. Arrange closer INR monitoring due to possible increased anticoagulation
CORRECT ANSWER: D — Arrange closer INR monitoring due to possible increased anticoagulation
Rationale: Fluconazole inhibits warfarin metabolism, notably CYP2C9; anticoagulant effect and bleeding risk
can increase, making closer INR surveillance and individualized adjustment appropriate.
Why the other options are incorrect:
A. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
B. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
C. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
INDEPENDENT PRACTICE RESOURCE • Page 3
, PHARMD / DRUG INTERACTIONS / 2026-2027
006. A patient taking metoprolol starts paroxetine. Which observation most suggests an interaction?
A. New bradycardia and dizziness from increased metoprolol exposure
B. Reduced paroxetine absorption caused by metoprolol
C. Persistent hypertension from beta-blocker receptor stimulation
D. Faster heart rate from reduced beta-blocker concentration
CORRECT ANSWER: A — New bradycardia and dizziness from increased metoprolol exposure
Rationale: Paroxetine is a strong CYP2D6 inhibitor and can raise metoprolol concentrations, increasing beta
blockade and causing symptomatic bradycardia or hypotension.
Why the other options are incorrect:
B. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
C. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
D. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
007. A patient taking clopidogrel after coronary stenting begins over-the-counter omeprazole. Which
concern should be reviewed?
A. Enhanced clopidogrel activation and spontaneous bleeding
B. Reduced formation of clopidogrel active metabolite
C. Irreversible blockade of aspirin absorption
D. Increased gastric acidity directly degrading clopidogrel
CORRECT ANSWER: B — Reduced formation of clopidogrel active metabolite
Rationale: Omeprazole inhibits CYP2C19, which is important for clopidogrel activation; consider a less
interacting acid suppressant and follow current product recommendations.
Why the other options are incorrect:
A. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
C. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
D. This proposed outcome or intervention is not the key expected interaction for the medicines and circumstances
described.
008. A hospitalized patient receiving oral midazolam is started on ritonavir-containing treatment. What
is the key issue?
A. Ritonavir chelation by oral midazolam
B. Complete loss of benzodiazepine receptor binding
C. Midazolam loss of effect through CYP3A induction
D. Markedly increased oral midazolam exposure and prolonged sedation
CORRECT ANSWER: D — Markedly increased oral midazolam exposure and prolonged sedation
Rationale: Ritonavir strongly inhibits CYP3A; oral midazolam coadministration can cause dangerous sedation
and respiratory depression and is generally contraindicated.
Why the other options are incorrect:
A. This proposed binding or chelation explanation does not describe the important interaction in this case.
B. This proposed binding or chelation explanation does not describe the important interaction in this case.
C. The proposed increase in metabolic clearance is not the primary documented effect of this combination.
INDEPENDENT PRACTICE RESOURCE • Page 4
