Medications is 35% of the scored PTCE (the PTCB exam). Answer 10 exam style questions on drug interactions and see exactly which concepts would cost you points on test day.
Start the 10 questions →A patient on warfarin says she has started eating large salads with spinach and kale every day. What effect can this sudden diet change have?
These questions cover drug-food interactions: warfarin and vitamin K, drug-drug interactions: warfarin and NSAIDs, herbal-drug interactions: ginkgo, drug-food interactions: MAOIs and tyramine and drug-drug interactions: MAOIs and OTC products. Each one shows the correct answer and why every other option is wrong, so a miss tells you exactly what to review before the PTCE.
Prefer to read first? Every question from the practice set above, with the correct answer and why each wrong option is wrong.
Answer: D. Leafy greens are rich in vitamin K, which counteracts warfarin. A sudden increase lowers the INR and raises clot risk. Patients are told to keep vitamin K intake consistent rather than avoid it.
Why not A: Diet matters a lot with warfarin; consistent vitamin K intake keeps the INR stable.
Why not B: More vitamin K works against warfarin, so the INR falls rather than rises.
Why not C: The interaction is about vitamin K opposing warfarin's effect, not absorption speed.
Exam tactic: Warfarin + vitamin K: keep intake CONSISTENT. More greens = lower INR.
Answer: B. NSAIDs such as ibuprofen inhibit platelets and can irritate the stomach lining. With warfarin, this increases the risk of serious bleeding, especially GI bleeding. The pharmacist should advise on a safer option.
Why not A: Ibuprofen does not reduce warfarin's effect; it adds to bleeding risk.
Why not C: Serotonin syndrome involves serotonergic drugs, not warfarin with an NSAID.
Why not D: High potassium is a concern with ACE inhibitors, ARBs or potassium-sparing diuretics.
Exam tactic: Anticoagulant + NSAID or aspirin = bleeding. Route to the pharmacist.
Answer: C. Ginkgo biloba has antiplatelet effects and has been linked to bleeding. Combined with warfarin or other blood thinners it can add to bleeding risk, so the pharmacist should counsel the patient.
Why not A: Ginkgo is not known for sharply raising blood sugar; bleeding is the concern.
Why not B: Ginkgo does not affect how warfarin tablets dissolve.
Why not D: Severe constipation is not the interaction of concern with ginkgo.
Exam tactic: Herbals that add bleeding risk: the four Gs (ginkgo, garlic, ginger, ginseng) plus fish oil and vitamin E.
Answer: A. MAOIs prevent the breakdown of tyramine, found in aged cheeses, cured or fermented meats, tap beer and soy sauce. Tyramine buildup can trigger a sudden, dangerous rise in blood pressure (hypertensive crisis).
Why not B: The problem is not reduced absorption; tyramine accumulation raises blood pressure.
Why not C: Low blood sugar is not the MAOI-tyramine reaction.
Why not D: Urine discoloration is not the MAOI-tyramine reaction.
Exam tactic: MAOI + tyramine (aged, fermented, cured) = hypertensive crisis.
Answer: C. Delsym contains dextromethorphan, which has serotonergic effects. With an MAOI (or within 2 weeks of stopping one) it can cause serotonin syndrome. OTC labels for dextromethorphan carry this warning.
Why not A: The warning is about dextromethorphan itself, not an alcohol reaction.
Why not B: The concern is a toxic serotonin reaction, not loss of antidepressant effect.
Why not D: Delsym does not contain a decongestant, and decongestants do not lower blood sugar.
Exam tactic: Patient on an MAOI: check OTC labels for dextromethorphan and decongestants.
Answer: B. Grapefruit juice inhibits the CYP3A4 enzyme in the intestine, so more simvastatin reaches the blood. Higher levels raise the risk of muscle damage (myopathy and, rarely, rhabdomyolysis).
Why not A: Grapefruit increases, not decreases, simvastatin levels.
Why not C: Grapefruit acts through enzyme inhibition, not by binding the drug like an antacid.
Why not D: A disulfiram-like reaction is caused by alcohol with drugs such as metronidazole.
Exam tactic: Grapefruit blocks CYP3A4 = drug levels go UP (simvastatin, lovastatin).
Answer: D. Calcium, magnesium, aluminum, iron and zinc bind fluoroquinolones and tetracyclines in the gut and reduce absorption. The doses must be spaced apart according to the labeling.
Why not A: The problem is managed by spacing doses; the antacid does not have to wait until the course ends.
Why not B: Taking them together blocks ciprofloxacin absorption and can cause treatment failure.
Why not C: The antacid reduces ciprofloxacin absorption; it does not make it toxic.
Exam tactic: Fluoroquinolones and tetracyclines + Ca/Mg/Al/Fe/Zn = chelation. Space doses.
Answer: A. St. John's wort induces liver enzymes (CYP3A4), lowering levels of many drugs, including hormonal contraceptives, which can lead to breakthrough bleeding and unintended pregnancy. It also adds serotonin syndrome risk with antidepressants.
Why not B: St. John's wort lowers, not raises, hormone levels.
Why not C: Severe low blood pressure is not the main St. John's wort interaction with contraceptives.
Why not D: St. John's wort does not convert contraceptives into sedatives.
Exam tactic: St. John's wort = enzyme inducer: other drugs go DOWN.
Answer: B. Alcohol with metronidazole can cause a disulfiram-like reaction: flushing, nausea, vomiting, abdominal cramps and headache. Patients avoid alcohol during therapy and for a period after, per labeling.
Why not A: Hypertensive crisis is the MAOI-tyramine reaction.
Why not C: Serotonin syndrome comes from serotonergic drug combinations.
Why not D: Hypoglycemia is not the classic metronidazole-alcohol reaction.
Exam tactic: Metronidazole + alcohol = disulfiram-like reaction. Auxiliary label: avoid alcohol.
Answer: D. Tramadol has serotonergic activity and lowers the seizure threshold. Combined with an SSRI such as sertraline, the risk of serotonin syndrome and seizures increases.
Why not A: A disulfiram-like reaction occurs with alcohol and drugs such as metronidazole.
Why not B: The main concern is toxicity from added serotonin, not loss of pain relief.
Why not C: Hyperkalemia is linked to ACE inhibitors, ARBs and potassium-sparing diuretics.
Exam tactic: Tramadol + SSRI/SNRI = serotonin syndrome and seizures.
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