PSI Patient Counselling & Drug Interactions 2

Question 1

A patient is prescribed ACE inhibitor ramipril and potassium-sparing diuretic spironolactone together. The risk is:

Accepted Answer

Hyperkalaemia — both drugs increase serum potassium

Answer

Both ACE inhibitors (reduce aldosterone-driven potassium excretion) and spironolactone (block aldosterone receptors) raise serum potassium. Combination increases hyperkalaemia risk — monitor electrolytes closely.

Question 2

When counselling a patient on oral combined contraceptive pills (COC), which advice is most important regarding missed pills?

Accepted Answer

If 2 or more pills are missed, use additional contraception for 7 days and consider emergency contraception depending on timing

Answer

Current FSRH guidance: if 2+ pills missed, contraceptive efficacy is reduced. Additional barrier contraception for 7 days and consideration of emergency contraception (if unprotected sex during pill-free week or start of pack) is advised.

Question 3

A patient on MAO inhibitor phenelzine is brought into the pharmacy having eaten aged cheese. They complain of severe headache. This suggests:

Accepted Answer

Hypertensive crisis due to tyramine interaction (cheese reaction)

Answer

MAO inhibitors block breakdown of dietary tyramine (found in aged cheese, fermented foods, red wine). Tyramine accumulation causes massive noradrenaline release, causing hypertensive crisis — a potentially fatal emergency.

Question 4

Which interaction should a pharmacist counsel a patient about when dispensing sildenafil for erectile dysfunction?

Accepted Answer

Absolute contraindication with organic nitrates (GTN, isosorbide) — risk of fatal hypotension

Answer

Both sildenafil (PDE-5 inhibition) and nitrates (cGMP elevation via guanylate cyclase) cause vasodilation. Combined, they produce profound, potentially fatal hypotension. Nitrates are an absolute contraindication.

Question 5

A patient on warfarin asks about taking cranberry juice. The pharmacist should advise:

Accepted Answer

Avoid large amounts — cranberry juice may inhibit CYP2C9, raising warfarin levels and INR

Answer

Cranberry juice, especially in large quantities, may inhibit CYP2C9 (warfarin's main metabolic pathway), increasing INR and bleeding risk. Case reports and pharmacovigilance data support caution with regular large intakes.

PSI Pharmacy Practice Test

PSI Pharmacy Practice Test

PSI Patient Counselling & Drug Interactions 2