Antimicrobial pharmacology, selection, dosing and stewardship in children — formative SAQs

SAQ 1 — Developmental pharmacokinetics, dosing and monitoring

Question 1 — 10 formative marks; suggested time 15 minutes [15]

A 3-week-old neonate born at 30 weeks gestation is treated for late-onset sepsis with vancomycin and gentamicin. The registrar consults you about the dosing and monitoring plan. Separately, a 4-year-old child (15 kg) on the ward is receiving vancomycin for a central-line-associated bloodstream infection, and the team asks whether trough monitoring alone is sufficient. [15] [16]

1. Explain how developmental pharmacokinetics changes vancomycin and gentamicin handling in this neonate compared to an older child. (3 marks)
2. Outline the weight-based dosing and therapeutic drug monitoring principles for vancomycin in the 4-year-old, including the AUC/MIC rationale. (3 marks)
3. Justify why extended-interval aminoglycoside dosing is appropriate in most children, and what evidence supports it. (2 marks)
4. Describe how you would use the WHO AWaRe framework to guide empiric selection in a previously well child with community-acquired pneumonia. (2 marks)

Full-credit answer — SAQ 1

Marking grid — SAQ 1

Common pitfalls — SAQ 1

• Quoting a fixed mg/kg dose without stating it must be age-adjusted and verified against the current formulary.
• Prescribing vancomycin by trough alone without mentioning AUC-guided monitoring.
• Forgetting that critically ill children may have augmented clearance requiring higher doses.
• Not knowing the Access, Watch, and Reserve categories or the 60 per cent target.

SAQ 2 — De-escalation, IV-to-oral switch, duration and delabeling

Question 2 — 10 formative marks; suggested time 15 minutes [1]

A 6-year-old with a complicated skin and soft tissue infection was started empirically on intravenous flucloxacillin and clindamycin. At 72 hours her cultures return Streptococcus pyogenes sensitive to penicillin. She is afebrile, eating, and improving, but her chart lists a penicillin allergy from infancy. [1] [10]

1. Describe your de-escalation plan from empiric to targeted therapy. (2 marks)
2. Justify whether and when to switch from IV to oral therapy, and which oral agent you would use. (3 marks)
3. Explain how you would assess and manage her reported penicillin allergy, including the evidence for delabeling. (3 marks)
4. Outline the shortest evidence-based duration and the stewardship safeguards that prevent over-treatment. (2 marks)

Full-credit answer — SAQ 2

Marking grid — SAQ 2

Common pitfalls — SAQ 2

• Continuing broad empiric therapy without de-escalating once the organism is known.
• Delaying oral switch in a child who meets the criteria, or using a low-bioavailability agent for stepdown.
• Accepting the penicillin allergy label without assessment, driving broader and more toxic therapy.
• Prescribing a long default duration without setting a documented stop date or review point.