PSA Renal and Hepatic Prescribing 1 — Questions and Answers
Question 1: A patient with CrCl 20 mL/min requires gentamicin therapy. What is the most appropriate dose adjustment strategy?
- Increase dose frequency while maintaining dose size
- Reduce dose and extend the dosing interval (Correct answer)
- Maintain standard dose with increased monitoring only
- Give a higher loading dose with standard intervals
Correct answer: Reduce dose and extend the dosing interval
In renal impairment, aminoglycosides require dose reduction and extended dosing intervals to prevent accumulation and nephrotoxicity/ototoxicity.
Question 2: Which of the following drugs does NOT typically require dose reduction in renal impairment?
- Metformin
- Gabapentin
- Rifampicin (Correct answer)
- Digoxin
Correct answer: Rifampicin
Rifampicin is primarily hepatically metabolized and excreted in bile, so it does not require dose reduction in renal impairment.
Question 3: A patient with Child-Pugh Class C cirrhosis requires sedation. Which benzodiazepine is most appropriate?
- Diazepam
- Chlordiazepoxide
- Lorazepam (Correct answer)
- Midazolam
Correct answer: Lorazepam
Lorazepam undergoes direct glucuronidation rather than hepatic oxidative metabolism, making it safer in severe liver disease where CYP450 activity is impaired.
Question 4: Which opioid is considered relatively safest for analgesia in a patient with severe renal impairment (eGFR <15 mL/min)?
- Morphine
- Codeine
- Tramadol
- Fentanyl (Correct answer)
Correct answer: Fentanyl
Fentanyl is metabolized to inactive metabolites that are not significantly renally excreted, making it safer than morphine or codeine in severe renal impairment.
Question 5: A patient with stage 4 CKD (eGFR 20 mL/min) is currently taking metformin for type 2 diabetes. What is the most appropriate action?
- Continue metformin at the standard dose
- Reduce metformin dose by 50%
- Stop metformin immediately (Correct answer)
- Switch to a sulfonylurea
Correct answer: Stop metformin immediately
Metformin is contraindicated when eGFR falls below 30 mL/min due to the risk of potentially fatal lactic acidosis from drug accumulation.
Question 6: Which of the following antihypertensives requires the greatest dose reduction in severe renal impairment compared to normal renal function?
- Amlodipine
- Atenolol (Correct answer)
- Losartan
- Verapamil
Correct answer: Atenolol
Atenolol is almost entirely renally excreted unchanged, requiring significant dose reduction to prevent accumulation and bradycardia in renal impairment.
Question 7: In hepatic impairment, what change occurs to the first-pass effect of orally administered drugs with high hepatic extraction ratios?
- It is increased, reducing oral bioavailability
- It is decreased, increasing oral bioavailability (Correct answer)
- It is unchanged as hepatocyte number remains constant
- It increases bioavailability only for acidic drugs
Correct answer: It is decreased, increasing oral bioavailability
Hepatic impairment reduces first-pass metabolism, allowing more of an orally administered high-extraction drug to reach systemic circulation, increasing bioavailability.
PSA Renal and Hepatic Prescribing 1
A patient with CrCl 20 mL/min requires gentamicin therapy.
What is the most appropriate dose adjustment strategy?