PSI Patient Counselling & Drug Interactions

Question 1

Which counselling point is most important for a patient starting a new SSRI for depression?

Accepted Answer

Antidepressant effect takes 2–4 weeks — continue even if no immediate improvement

Answer

Stop the medication if side effects occur in week 1

Answer

SSRIs work immediately

Answer

Take double dose if you miss a day

Question 2

A patient asks why they must avoid grapefruit juice with their simvastatin. The pharmacist explains:

Accepted Answer

Grapefruit inhibits CYP3A4 in the intestinal wall, raising simvastatin plasma levels and increasing myopathy risk

Answer

Grapefruit reduces simvastatin absorption

Answer

Grapefruit increases renal excretion of simvastatin

Answer

Grapefruit causes a taste interaction only

Question 3

Which drug interaction mechanism underlies the interaction between antacids and fluoroquinolone antibiotics?

Accepted Answer

Chelation — antacid cations (Al3+, Mg2+) complex with fluoroquinolones reducing oral absorption

Answer

Antacids induce CYP enzymes

Answer

Competition for protein binding

Answer

Fluoroquinolones inhibit antacid neutralisation

Question 4

A patient on phenytoin is started on fluconazole. Which outcome should the pharmacist anticipate?

Accepted Answer

Increased phenytoin levels (risk of toxicity) — fluconazole inhibits CYP2C9

Answer

Decreased phenytoin levels

Answer

No interaction — phenytoin levels unchanged

Answer

Fluconazole levels increase only

Question 5

Which patient counselling approach best ensures medication adherence in a patient with low health literacy?

Accepted Answer

Simple verbal instructions with demonstrate-and-return demonstration, written pictogram leaflets

Answer

Providing a detailed written clinical summary

Answer

Referring all low-literacy patients to a specialist

Answer

Only verbal instructions in a loud, clear voice

Question 6

Which drug interaction between methotrexate and NSAIDs is clinically significant?

Accepted Answer

NSAIDs reduce renal methotrexate clearance, causing toxicity (mucositis, myelosuppression)

Answer

NSAIDs reduce methotrexate absorption

Answer

NSAIDs enhance methotrexate efficacy safely

Answer

No clinically relevant interaction