PSI Patient Counselling & Drug Interactions 3

Question 1

A patient taking isotretinoin for severe acne must be counselled about which mandatory precaution?

Accepted Answer

Strict contraception throughout treatment and for one month after — severe teratogen

Answer

Isotretinoin is teratogenic. In Ireland, the HPRA-mandated iPLEDGE-equivalent (Roaccutane/Accutane REMS) requires two forms of contraception, monthly pregnancy testing and patient agreement form.

Question 2

Which antibiotic should not be prescribed with warfarin without close INR monitoring?

Accepted Answer

Ciprofloxacin — inhibits CYP1A2 and CYP2C9, raising warfarin levels significantly

Answer

Ciprofloxacin inhibits multiple CYP enzymes that metabolise warfarin, reducing its clearance. INR can rise substantially, increasing bleeding risk. Enhanced INR monitoring is required.

Question 3

A patient prescribed lithium is starting ibuprofen for back pain. The pharmacist should:

Accepted Answer

Advise against ibuprofen — recommend paracetamol instead, and monitor for lithium toxicity signs

Answer

NSAIDs reduce renal lithium clearance, raising plasma levels into the toxic range within days. Paracetamol is the safe alternative. If NSAIDs are essential, lithium levels must be monitored closely.

Question 4

Which counselling point is essential for a patient using transdermal hormone patches?

Accepted Answer

Rotate application sites, apply to clean dry skin and press firmly for 30 seconds — avoid same site for at least one week

Answer

Site rotation prevents skin irritation and maintains consistent drug absorption. Clean, dry, non-hairy skin (e.g., lower abdomen, upper arm) maximises adhesion. Intervals between uses of the same site allow skin recovery.

Question 5

Which combination of antibiotics produces significant risk of QT interval prolongation and ventricular arrhythmia?

Accepted Answer

Azithromycin combined with moxifloxacin

Answer

Both azithromycin and moxifloxacin individually prolong QT interval. Co-administration significantly increases risk of torsades de pointes — a potentially fatal ventricular arrhythmia. Avoid combining QT-prolonging agents.

PSI Pharmacy Practice Test

PSI Pharmacy Practice Test

PSI Patient Counselling & Drug Interactions 3