Saudi Prometric Pharmacist Drug Interactions and Adverse Effects

Question 1

A patient on warfarin starts taking fluconazole for a vaginal yeast infection. What is the expected pharmacokinetic interaction?

Accepted Answer

Fluconazole inhibits CYP2C9, increasing warfarin levels and INR — increased bleeding risk

Answer

Fluconazole induces CYP2C9, decreasing warfarin levels

Answer

No interaction — fluconazole only affects CYP3A4

Answer

Fluconazole enhances warfarin absorption from the GI tract

Question 2

Which adverse effect is associated with ACE inhibitor therapy and is caused by bradykinin accumulation?

Accepted Answer

Dry, persistent cough — occurs in 10–15% of patients

Answer

Hyperkalemia — due to aldosterone reduction

Answer

Renal insufficiency — in bilateral renal artery stenosis

Answer

Angioedema — life-threatening, rare (0.1–0.5%)

Question 3

A patient taking MAO inhibitors (phenelzine) eats tyramine-rich food. What reaction occurs?

Accepted Answer

Hypertensive crisis — tyramine cannot be metabolized, causes massive norepinephrine release

Answer

Hypotension and bradycardia

Answer

Serotonin syndrome

Answer

Peripheral neuropathy

Question 4

Which class of drugs can cause hyperkalemia when combined with ACE inhibitors or ARBs?

Accepted Answer

Potassium-sparing diuretics and aldosterone antagonists (spironolactone, eplerenone)

Answer

Thiazide diuretics

Answer

Loop diuretics

Answer

Beta-blockers

Question 5

A patient taking lithium is prescribed ibuprofen for joint pain. What should the pharmacist advise?

Accepted Answer

Avoid NSAIDs — they increase lithium levels via renal prostaglandin inhibition; use paracetamol instead

Answer

NSAIDs are safe with lithium — no significant interaction

Answer

Use low-dose ibuprofen only — safe at <400 mg/day

Answer

Increase fluid intake when taking ibuprofen with lithium

Question 6

A patient on methotrexate is prescribed trimethoprim for a urinary tract infection. What is the major concern?

Accepted Answer

Additive folate antagonism causing severe myelosuppression and mucositis

Answer

Methotrexate reduces trimethoprim renal excretion

Answer

Trimethoprim induces methotrexate metabolism, reducing efficacy

Answer

No significant interaction — different mechanisms