Pharmacy Drug Interactions 3

Question 1

Rifampin is a potent inducer of CYP450 enzymes. When a patient on oral contraceptives starts rifampin, you should warn them about:

Accepted Answer

Decreased contraceptive efficacy and risk of unintended pregnancy

Answer

Increased contraceptive efficacy

Answer

Higher risk of thromboembolism

Answer

Severe skin rash from the combination

Question 2

The combination of sildenafil and nitrates is contraindicated because it can cause:

Accepted Answer

Severe hypotension

Answer

Severe hypertension

Answer

Renal failure

Answer

Hepatotoxicity

Question 3

Which drug interaction occurs when phenytoin decreases the effect of doxycycline by increasing its metabolism?

Accepted Answer

CYP enzyme induction

Answer

Pharmacodynamic antagonism

Answer

CYP enzyme inhibition

Answer

Protein binding displacement

Question 4

Lithium toxicity risk increases when a patient starts a thiazide diuretic because:

Accepted Answer

Thiazides cause sodium depletion, leading to compensatory lithium reabsorption

Answer

Thiazides increase lithium renal excretion

Answer

Thiazides block lithium's mechanism of action

Answer

The combination causes serotonin syndrome

Question 5

A patient taking digoxin begins amiodarone therapy. What adjustment is typically needed?

Accepted Answer

Decrease the digoxin dose by approximately 50%

Answer

Increase the digoxin dose

Answer

Discontinue digoxin immediately

Answer

No change is necessary

Question 6

Taking an MAOI within 14 days of starting meperidine can cause which life-threatening reaction?

Accepted Answer

Serotonin syndrome / hyperpyrexic crisis

Answer

Anticholinergic crisis

Answer

Neuroleptic malignant syndrome

Answer

Torsades de pointes