Paeds · clinical-pharmacology-and-therapeutics
Therapeutic drug monitoring
Also known as Drug level monitoring in children · TDM in paediatrics · Therapeutic drug monitoring · Vancomycin and gentamicin monitoring · Phenytoin level monitoring
A fellowship approach to therapeutic drug monitoring in children covering why narrow-therapeutic-index drugs such as aminoglycosides, vancomycin, phenytoin, digoxin and tacrolimus are monitored, how developmental pharmacokinetics and the maturation of glomerular filtration move a level, how linear and Michaelis-Menten nonlinear kinetics differ, the vancomycin area-under-the-curve target, extended-interval aminoglycoside dosing, the phenytoin free fraction in hypoalbuminaemia, and the correct sampling times for a true trough, peak and steady-state level.
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Target exams
Red flags
- Vancomycin or aminoglycoside prescribed without weight-based dosing and a documented plan to check a level
- Drug level drawn during the infusion, from the infusing line, or at the wrong time and acted on as if valid
- Phenytoin total level reported and acted on without accounting for hypoalbuminaemia and the free fraction
- Aminoglycoside continued in a child with a rising creatinine or falling urine output without a level
- Vancomycin trough used as the sole target for serious MRSA infection when area-under-curve monitoring is available
- Dose adjusted on a single number without confirming the time of the last dose and the sample
Life stages
Care settings
Clinical exam formats
Board mappings
- General and Community Paediatrics
- Current 2026 PREP curriculum — Learning Objective 2.2.1: Recognise, prioritise and manage an acutely ill infant, child or young person
- Current 2026 PREP curriculum — Learning Objective: Safe prescribing and medication management in infants, children and young people
- Renewed curriculum for first-year trainees from 2027 — Learning goal 6: Clinical management – essential general paediatrics
- Renewed curriculum for first-year trainees from 2027 — Learning goal 9: Quality and safety, including medication safety
- Clinical Applications
- Medical Sciences
- Long Cases
- Short Cases
- 4. Professional skills and knowledge: Patient management
- 7. Patient safety, including safe prescribing
- 8. Quality improvement and patient safety
- General Paediatrics: Prescribes and monitors medicines safely, using weight-based dosing and therapeutic drug monitoring where indicated
- Foundation of Practice (FOP)
- Theory and Science (TAS)
- Applied Knowledge in Practice (AKP)
- Clinical
- History
- Communication
- General Pediatrics Content Outline — Domain 10: Principles of Pharmacology and Medication Management
- General Pediatrics Content Outline — Domain 9: Infectious Diseases
- General Pediatrics Content Outline — Universal Task 4: Management and Treatment
- Systems-Based Practice 2: Antimicrobial Stewardship
- Patient Safety/Quality Improvement 1: Medication Safety
- Medical Knowledge 2: Diagnostic and Therapeutic Decision Making
- Medical Expert
- Pharmacist
- Pediatrics: Core EPA #5 — Recommending and Initiating Pharmacologic Interventions
Overview & Definition
Picture a three-year-old on a gentamicin drip for a urinary tract infection, a neonate on vancomycin for a line infection, and a ten-year-old on phenytoin for epilepsy. Each child carries a drug whose healing dose and its harmful dose sit close together. Therapeutic drug monitoring is the discipline that keeps those children in the safe gap between the two. [6] [7]
A drug earns monitoring when two things are true at once. First, the dose that achieves the effect and the dose that causes harm lie close together — a narrow therapeutic index. Second, the blood concentration predicts the effect better than the dose alone does, because between the dose written and the level reached stand absorption, distribution, metabolism, excretion, age, organ function, interactions and adherence. Aminoglycosides, vancomycin and phenytoin meet both tests; amoxicillin does not, because a wide gap separates its effective dose from any toxic dose. [6] [7]
From the first dose to a safe, on-target level
- 1
1 · Dose by weight and age
Prescribe a weight-based loading and maintenance dose, age-adjusted for developmental pharmacokinetics and organ function.
- 2
2 · Reach steady state
Wait four to five half-lives (for vancomycin, usually around the fourth dose) before interpreting a maintenance level, unless a post-load level is needed urgently.
- 3
3 · Sample at the true trough
Draw the trough immediately before the next dose, from a clean line, not during the infusion.
- 4
4 · Compare to the target
Match the level to the age-specific target: AUC for vancomycin, peak for aminoglycosides, range for anticonvulsants.
- 5
5 · Adjust and recheck
Change the dose or interval using pharmacokinetics or a Bayesian tool, then recheck after steady state is re-established.
References11ShowHide
- [1]Rybak MJ, Le J, Lodise TP, et al. Therapeutic Monitoring of Vancomycin for Serious Methicillin-resistant Staphylococcus aureus Infections: A Revised Consensus Guideline and Review by the American Society of Health-system Pharmacists, the Infectious Diseases Society of America, the Pediatric Infectious Diseases Society, and the Society of Infectious Diseases Pharmacists. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 2020.PMID 32658968
- [2]He CY, Ye PP, Liu B, et al. Population Pharmacokinetics and Dosing Optimization of Vancomycin in Infants, Children, and Adolescents with Augmented Renal Clearance. Antimicrobial agents and chemotherapy, 2021.PMID 34339268
- [3]Camaione L, Elliott K, Mitchell-Van Steele A, et al. Vancomycin dosing in children and young adults: back to the drawing board. Pharmacotherapy, 2013.PMID 24019205
- [4]Nestaas E, Bangstad HJ, Sandvik L, et al. Aminoglycoside extended interval dosing in neonates is safe and effective: a meta-analysis. Archives of disease in childhood Fetal and neonatal edition, 2005.PMID 15857879
- [5]Contopoulos-Ioannidis DG, Giotis ND, Baliatsa DV, et al. Extended-interval aminoglycoside administration for children: a meta-analysis. Pediatrics, 2004.PMID 15231982
- [6]Jenh AM, Tamma PD, Milstone AM Extended-interval aminoglycoside dosing in pediatrics. The Pediatric infectious disease journal, 2011.PMID 21407038
- [7]Kearns GL, Abdel-Rahman SM, Alander SW, et al. Developmental pharmacology--drug disposition, action, and therapy in infants and children. The New England journal of medicine, 2003.PMID 13679531
- [8]Ludden TM Nonlinear pharmacokinetics: clinical Implications. Clinical pharmacokinetics, 1991.PMID 2044328
- [9]Patsalos PN, Zugman M, Lake C, et al. Serum protein binding of 25 antiepileptic drugs in a routine clinical setting: A comparison of free non-protein-bound concentrations. Epilepsia, 2017.PMID 28542801
- [10]Tasa T, Metsvaht T, Kalamees R, et al. DosOpt: A Tool for Personalized Bayesian Dose Adjustment of Vancomycin in Neonates. Therapeutic drug monitoring, 2017.PMID 29084032
- [11]Dao K, Guidi M, André P, et al. Optimisation of vancomycin exposure in neonates based on the best level of evidence. Pharmacological research, 2020.PMID 31108184