Carbamazepine TDM – Trough Level — SCE Neurology MCQ
Instant feedback + full explanation. One question, done properly.
Educational content. Not a substitute for clinical judgement or local policy.
Reveal the answer and explanation
Correct answer: A — Steady-state trough sampled immediately before the next dose
The best answer is “Steady-state trough sampled immediately before the next dose”. A pre-dose trough at steady state gives the most reproducible comparison with the reference range; interpretation must also include dose timing, auto-induction, active metabolite, symptoms, sodium and interacting drugs. “Immediate post-dose sample during the absorption phase” is less appropriate because a post-dose sample reflects absorption and may overstate baseline exposure “Random sample without documented dose or collection time” is less appropriate because undocumented random timing prevents meaningful serial comparison “Sample obtained during a habitual clinical seizure” is less appropriate because toxicity or interaction concerns justify testing outside seizures “Two-hour post-dose sample as the routine trough concentration” is less appropriate because a fixed two-hour sample is near absorption rather than a trough for many formulations
Reference: Tegretol 200 mg tablets: SmPC. https://www.medicines.org.uk/emc/product/7844/smpc