Dosing in renal failure and extracorporeal drug removal MCQs With Answer

This MCQ set on dosing in renal failure and extracorporeal drug removal is designed for M.Pharm students studying Clinical Pharmacokinetics and Therapeutic Drug Monitoring. It focuses on principles that guide dose selection and timing in impaired renal function, factors determining drug removal by hemodialysis, CRRT, peritoneal dialysis and plasmapheresis, and practical approaches including loading dose strategy, use of fraction excreted, sieving coefficients, and monitoring. The questions integrate mechanistic understanding with clinical application—when to adjust maintenance doses, how extracorporeal modalities change clearance, and how to interpret therapeutic drug monitoring to optimize efficacy and minimize toxicity.

Q1. Which principle most often applies to administering a loading dose in patients with renal failure?

• Reduce the loading dose proportional to creatinine clearance
• Increase the loading dose due to reduced clearance
• Loading dose is usually unchanged because it depends primarily on volume of distribution
• Omit the loading dose until steady state is achieved

Correct Answer: Loading dose is usually unchanged because it depends primarily on volume of distribution

Q2. Among the listed drug properties, which most strongly predicts removal by intermittent hemodialysis?

• High plasma protein binding (>90%)
• Large molecular weight (>50 kDa)
• Low volume of distribution (small Vd, e.g., <1 L/kg)
• High lipid solubility

Correct Answer: Low volume of distribution (small Vd, e.g., <1 L/kg)

Q3. What is the sieving coefficient in the context of hemofiltration?

• The ratio of drug removed by adsorption to drug in plasma
• The ratio of drug concentration in ultrafiltrate to plasma concentration (reflecting free fraction)
• The ratio of dialysate flow to blood flow
• The percentage of total body drug in the extracellular fluid

Correct Answer: The ratio of drug concentration in ultrafiltrate to plasma concentration (reflecting free fraction)

Q4. How does high plasma protein binding (>90%) generally affect extracorporeal removal during hemodialysis?

• It increases dialysis clearance because albumin-bound drug is readily filtered
• It has minimal effect; highly protein-bound drugs are usually not significantly removed by dialysis
• It enhances convective removal more than diffusive removal
• It leads to greater removal during peritoneal dialysis vs hemodialysis

Correct Answer: It has minimal effect; highly protein-bound drugs are usually not significantly removed by dialysis

Q5. For a drug known to be substantially removed by hemodialysis, what is the preferred dosing strategy surrounding an intermittent dialysis session?

• Administer the maintenance dose immediately before dialysis
• Administer the maintenance dose during dialysis to maintain steady levels
• Administer the maintenance dose after dialysis to avoid its removal
• No timing adjustment is necessary

Correct Answer: Administer the maintenance dose after dialysis to avoid its removal

Q6. Which is the recommended general approach to aminoglycoside dosing in severe renal impairment?

• Reduce the loading dose but keep the same dosing interval
• Give the usual loading dose and extend the dosing interval based on renal clearance and TDM
• Stop aminoglycosides entirely and never use them
• Double the maintenance dose to overcome reduced clearance

Correct Answer: Give the usual loading dose and extend the dosing interval based on renal clearance and TDM

Q7. How is drug clearance during continuous renal replacement therapy (CRRT) best characterized compared with intermittent hemodialysis?

• CRRT provides intermittent high clearance only during treatment hours
• CRRT provides continuous clearance roughly approximated by the effluent flow rate and may require higher total daily dosing
• CRRT does not remove drugs at all because it is convective only
• CRRT clearance equals native renal clearance and therefore requires no dose change

Correct Answer: CRRT provides continuous clearance roughly approximated by the effluent flow rate and may require higher total daily dosing

Q8. What is the main difference between high-flux and low-flux dialysis membranes relevant to drug removal?

• High-flux membranes have smaller pores and remove fewer solutes
• High-flux membranes remove larger ‘middle’ molecules and can increase clearance of some drugs compared with low-flux membranes
• Low-flux membranes are superior for removing protein-bound drugs
• There is no difference in drug removal between high-flux and low-flux membranes

Correct Answer: High-flux membranes remove larger ‘middle’ molecules and can increase clearance of some drugs compared with low-flux membranes

Q9. Which extracorporeal technique is most likely to remove highly protein-bound or very large molecules?

• Conventional low-flux hemodialysis
• Haemodiafiltration at low effluent rates
• Therapeutic plasma exchange (plasmapheresis)
• Peritoneal dialysis with short dwell times

Correct Answer: Therapeutic plasma exchange (plasmapheresis)

Q10. For a drug with substantial hepatic metabolism and only minor renal excretion, how should maintenance dosing change in renal failure?

• Large dose reduction is always required because renal failure affects all clearances
• No adjustment or minimal adjustment is usually needed since nonrenal clearance predominates
• Switch to continuous infusion regardless of renal function
• Reduce loading dose substantially but maintain frequent maintenance dosing

Correct Answer: No adjustment or minimal adjustment is usually needed since nonrenal clearance predominates

Q11. Which nomogram or method uses the fraction of drug excreted unchanged in urine (fe) to estimate maintenance dose adjustments in renal impairment?

• Beer-Lambert method
• Dettli method (fractional renal clearance approach)
• Henderson-Hasselbalch equation
• Fick’s first law

Correct Answer: Dettli method (fractional renal clearance approach)

Q12. If a drug has a very large volume of distribution (e.g., Vd >> total body water), what is the expected impact of hemodialysis on its plasma concentrations?

• Hemodialysis will rapidly and substantially reduce total body drug stores
• Hemodialysis will cause rebound increases due to redistribution
• Hemodialysis will have minimal immediate effect because most drug is outside the vascular compartment
• Hemodialysis will convert the drug to inactive metabolites

Correct Answer: Hemodialysis will have minimal immediate effect because most drug is outside the vascular compartment

Q13. In continuous venovenous hemofiltration (CVVH), which operational parameter most directly determines solute clearance for an unbound small molecule?

• Dialysate glucose concentration
• Ultrafiltration (effluent) rate
• Duration of the blood pump priming
• Patient body temperature

Correct Answer: Ultrafiltration (effluent) rate

Q14. For vancomycin dosing in a patient on intermittent high-flux hemodialysis, what is an appropriate strategy?

• Give only a loading dose and never re-dose during therapy
• Give a loading dose then administer maintenance/supplemental doses after dialysis sessions and use TDM to guide dosing
• Give continuous infusion through the dialysis circuit
• Administer vancomycin only during dialysis to maximize removal

Correct Answer: Give a loading dose then administer maintenance/supplemental doses after dialysis sessions and use TDM to guide dosing

Q15. Which factor is most important for drug removal during peritoneal dialysis?

• Patient age only
• Peritoneal membrane transport characteristics and dwell time
• Dialyzer surface area (hemodialysis parameter)
• Pore size of a synthetic dialysis membrane

Correct Answer: Peritoneal membrane transport characteristics and dwell time

Q16. How can adsorption to an extracorporeal circuit affect drug disposition?

• Adsorption does not occur with modern circuits
• Adsorption may cause significant early loss of drug unrelated to pore size or clearance rates, especially for lipophilic drugs
• Adsorption increases systemic clearance proportionally to molecular weight
• Adsorption only affects aqueous solutes and not protein-bound drugs

Correct Answer: Adsorption may cause significant early loss of drug unrelated to pore size or clearance rates, especially for lipophilic drugs

Q17. A drug is 70% renally excreted unchanged (fe = 0.7). If the patient’s renal function is reduced to 25% of normal, approximately what fraction of the usual maintenance dose should be given using a simple proportional adjustment?

• Approximately 25% of the usual maintenance dose
• Approximately 75% of the usual maintenance dose
• Approximately 48% of the usual maintenance dose
• No change; give 100% of the usual maintenance dose

Correct Answer: Approximately 48% of the usual maintenance dose

Q18. What is the typical effect of veno-arterial extracorporeal membrane oxygenation (ECMO) on drug pharmacokinetics relevant to dosing?

• ECMO always decreases volume of distribution for all drugs
• ECMO circuits can increase apparent volume of distribution and sequester lipophilic drugs, altering initial concentrations and clearance
• ECMO increases renal clearance directly and reduces need for dose adjustment
• ECMO eliminates the need for therapeutic drug monitoring

Correct Answer: ECMO circuits can increase apparent volume of distribution and sequester lipophilic drugs, altering initial concentrations and clearance

Q19. How does hemodiafiltration (convective + diffusive) differ from pure diffusion-based dialysis in terms of drug removal?

• Convective clearance favors removal of larger middle molecules compared with diffusion alone
• Convective clearance removes only protein-bound drugs
• Diffusion removes larger molecules better than convection
• There is no difference in solute selectivity between convective and diffusive methods

Correct Answer: Convective clearance favors removal of larger middle molecules compared with diffusion alone

Q20. For drugs with narrow therapeutic indices in patients with renal failure and extracorporeal therapies, which monitoring strategy is most informative for dose optimization?

• Single random concentration measurement without context
• Therapeutic drug monitoring guided by AUC (area under the curve) and timing relative to dialysis
• Rely solely on creatinine clearance trends without drug levels
• Measure only peak levels and ignore troughs or AUC

Correct Answer: Therapeutic drug monitoring guided by AUC (area under the curve) and timing relative to dialysis

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