MAC Value — FRCA Primary MCQ
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Correct answer: B — 2.1%
The correct answer is B: 2.1%. Current UK product information gives an average sevoflurane MAC in oxygen of 2.1% at 40 years of age. MAC is the steady-state alveolar concentration that prevents purposeful movement in response to a standard surgical stimulus in 50% of subjects. It is age-dependent and decreases as age increases. Nitrous oxide has an additive anaesthetic effect: with 65% nitrous oxide, the sevoflurane MAC at age 40 is approximately 1.1%, making D closer to the nitrous-oxide value rather than the oxygen value. Values around 6% and 104% correspond approximately to desflurane and nitrous oxide respectively, while 0.75% is associated with halothane.
Reference: electronic Medicines Compendium, Sevoflurane 100% Inhalation Vapour, liquid, Summary of Product Characteristics, section 4.2 and Table 1, updated 2026. https://www.medicines.org.uk/emc/product/9780/smpc