SAQ 1 — Definitions, the formulation gap and the stepwise pathway

Stem (20 marks; suggested 15 minutes): [2]

A 6-year-old renal transplant recipient has had erratic tacrolimus levels for three months despite a "correct" weight-based dose. At clinic the registrar asks the mother how the child actually takes the medicine; she reports that he spits out the bitter liquid and the half-tablets crumble. [1] [2]

(a) Define medication adherence, distinguish it from compliance and persistence, and name the three dimensions of adherence. (8 marks) [2]

(b) Outline the stepwise formulation-and-adherence management pathway the registrar should run at this clinic visit. (8 marks) [2]

(c) Explain why an erratic tacrolimus level should be treated as adherence-until-proven-otherwise, and name two objective markers of adherence. (4 marks) [2]

Model answer — SAQ 1

(a) Definitions and dimensions (8 marks). [2]

• Medication adherence — the extent to which a person's medicine-taking behaviour corresponds to the agreed recommendations; shared, negotiated and behavioural. (2 marks)
• Adherence versus compliance — adherence is shared and negotiated; compliance is the older, discouraged term implying the patient obeys the prescriber (and is therefore the prescriber's "fault-free" framing). (2 marks)
• Persistence — the length of time a patient continues to take the medicine before stopping; a separate dimension from day-to-day implementation. (1 mark)
• Three dimensions (ABC taxonomy) — initiation (taking the first dose), implementation (taking it as prescribed day to day), discontinuation (stopping). Non-adherence can sit in any one. (3 marks) [2]

(b) Stepwise pathway (8 marks — 1 mark per named step, capped at 8). [2]

1. Assess adherence openly and without blame — ask how does your child actually take this medicine?; triangulate with an objective marker (tacrolimus level). [2]
2. Identify the barrier — here the barrier is the formulation (bitter liquid, crumbling split tablets), with possible regimen and family layers. [1]
3. Match the formulation to the child — explore a taste-masked liquid, a dispersible preparation, or a mini-tablet at a strength that allows weight-based dosing; involve the pharmacist. [9]
4. Simplify the regimen — tacrolimus is twice-daily by nature, but align doses with daily routines (mealtimes, tooth-brushing) and provide dosing aids. [2]
5. Counsel the child and family — explain the rationale, teach technique, offer taste-masking, and (because this is a six-year-old) include the child in the conversation. [3]
6. Review and reinforce — re-assess adherence and the level at every visit; adjust the formulation as the child grows. [2]

(c) Erratic level as adherence signal (4 marks). [2]

• An erratic or unexpectedly low drug level on a stable dose is near-pathognomonic for intermittent dosing; chasing it with dose escalation produces toxicity once the child briefly becomes adherent, so the level should be treated as adherence-until-proven-otherwise and re-assessed before any dose change. (2 marks)
• Two objective markers: therapeutic drug monitoring (the tacrolimus level itself), and pharmacy refill records or electronic dosing monitors; in some diseases, a disease biomarker (here, creatinine / graft function) is a third. (2 marks) [2]

SAQ 2 — Palatability, age-appropriate formulations and excipient safety

Stem (20 marks; suggested 15 minutes): [1]

A fellowship examiner asks: "Why is the formulation half of adherence in children, and how do you choose an age-appropriate formulation — including in a neonate?" [1] [3]

(a) Explain the developmental and formulation reasons why a medicine an adult tolerates may be genuinely untakeable for a young child. (8 marks) [3]

(b) Describe how the choice of formulation should change across the paediatric age range (neonate, toddler/preschool, school-age, adolescent), citing named evidence where relevant. (8 marks) [6] [9]

(c) Outline the excipient-safety principle in neonates, name three classical offending excipients, and name the database that systematises excipient safety. (4 marks) [5]

Model answer — SAQ 2

(a) Developmental and formulation reasons (8 marks). [3]

• Taste and palatability — children are biologically more bitter-sensitive than adults (an evolutionary poison protection); most active pharmaceutical ingredients are intensely bitter, and a liquid an adult tolerates may be genuinely untakeable for a two-year-old (Mennella 2008, 2013). (3 marks) [3]
• Swallowing readiness — safe swallowing of a standard tablet is a developmental skill acquired around five to six years with wide variability; a tablet for a four-year-old is a formulation failure, not a child failure. (2 marks)
• The formulation gap (Nunn 2005) — many drugs have no age-appropriate liquid, no palatable form, and no strength-correct dose, so they are crushed, split, diluted or forced. (2 marks) [1]
• Regimen burden compounds the formulation burden — a bitter liquid given four times daily is harder than the same drug given once daily. (1 mark)

(b) Formulation across the age range (8 marks — 2 per band). [6] [9]

• Neonates — excipient safety is the first question (benzyl alcohol, propylene glycol, ethanol); prefer formulations free of these, check the STEP database, and involve the pharmacist on dilution and compounding. (2 marks) [6]
• Toddlers and preschool children — prefer a taste-masked liquid, a dispersible tablet, or a mini-tablet (2 mm), which many young children can swallow from about two years; the default is no longer "always a liquid" (Münch 2023). (2 marks) [9]
• School-age children — chewable and dispersible tablets bridge, then standard tablets once swallowing is reliable; simplify toward before-school and bedtime dosing to avoid school-hour doses (Palmeirim 2020 chewable mebendazole trial). (2 marks) [7]
• Adolescents — standard tablets or capsules; long-acting once-daily or long-acting injectable formulations outperform short-acting frequent dosing; structured transition and an honest conversation are the best-evidenced adherence interventions (Edgcomb 2018). (2 marks) [12]

(c) Excipient safety in neonates (4 marks). [5]

• Principle — neonates handle excipients differently from older children and adults because of immature hepatic metabolism and renal clearance, so excipients tolerated elsewhere can cause real harm in a neonate. (1 mark) [6]
• Three classical offending excipients — benzyl alcohol (gasping syndrome), propylene glycol (hyperosmolality, neurological toxicity), and ethanol; high sorbitol causes osmotic diarrhoea. (2 marks) [6]
• Named database — the STEP (Safety and Toxicity of Excipients for Paediatrics) database (Salunke 2013) systematises excipient safety across paediatric formulations and is the reference to name. (1 mark) [5]