PSA Drug Interactions 1 — Questions and Answers
Question 1: What is a drug-drug interaction?
- When one drug affects the activity of another when both are administered together (Correct answer)
- When a drug interacts with food
- When a drug causes an allergic reaction
- When a drug expires
Correct answer: When one drug affects the activity of another when both are administered together
Drug-drug interactions occur when one medication modifies the effect of another, potentially causing increased toxicity, reduced efficacy, or unexpected adverse effects.
Question 2: What enzyme system is most commonly involved in drug metabolism interactions?
- Cytochrome P450 (CYP450) enzyme system (Correct answer)
- Digestive enzymes
- Respiratory enzymes
- Cardiac enzymes
Correct answer: Cytochrome P450 (CYP450) enzyme system
The CYP450 system in the liver is responsible for metabolizing most drugs, and interactions involving CYP inducers or inhibitors are the most clinically significant.
Question 3: What happens when a CYP450 inhibitor is given with a substrate drug?
- The substrate drug level increases because its metabolism is slowed (Correct answer)
- The substrate drug level decreases
- No effect occurs
- The inhibitor stops working
Correct answer: The substrate drug level increases because its metabolism is slowed
CYP450 inhibitors block the enzyme, reducing metabolism of the substrate drug, leading to higher blood levels and potentially increased toxicity.
Question 4: Why is warfarin particularly prone to drug interactions?
- It has a narrow therapeutic index, is highly protein-bound, and is metabolized by multiple CYP enzymes (Correct answer)
- It is always given in high doses
- It is not absorbed orally
- It has no known interactions
Correct answer: It has a narrow therapeutic index, is highly protein-bound, and is metabolized by multiple CYP enzymes
Warfarin's narrow therapeutic window means small changes in drug levels can cause serious bleeding or therapeutic failure, and many factors affect its metabolism.
Question 5: What is the interaction between ACE inhibitors and potassium-sparing diuretics?
- Both increase potassium levels, risking dangerous hyperkalemia (Correct answer)
- They cancel each other out
- They decrease potassium levels
- No interaction exists
Correct answer: Both increase potassium levels, risking dangerous hyperkalemia
ACE inhibitors reduce aldosterone-mediated potassium excretion, while potassium-sparing diuretics prevent potassium loss. Together they can cause dangerous hyperkalemia.
Question 6: What is serotonin syndrome?
- A potentially life-threatening condition caused by excessive serotonin, often from combining serotonergic drugs (Correct answer)
- A mild headache from antidepressants
- A withdrawal symptom
- An allergic reaction
Correct answer: A potentially life-threatening condition caused by excessive serotonin, often from combining serotonergic drugs
Serotonin syndrome results from excessive serotonergic activity, caused by combining drugs like SSRIs with MAOIs, tramadol, or triptans. Symptoms include agitation, hyperthermia, and clonus.
PSA Drug Interactions 1
What is a drug-drug interaction?