MAC Age Reduction Calculation — FRCA Primary MCQ

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HardPharmacology - Inhalational AgentsMAC Age Reduction CalculationFRCA Primary

MAC of sevoflurane is reduced by approximately 6% per decade of age after age 40. A 70-year-old would have an approximate MAC of:

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Correct answer: D — 1.6%

MAC at age 40 is 2.0%. Three decades of reduction at 6% per decade: 2.0 × (1 - 0.06)³ = 2.0 × 0.83 = 1.66% ≈ 1.6%. Alternatively: 3 decades × 6% = 18% reduction / 2.0 - (2.0 × 0.18) = 2.0 - 0.36 = 1.64%. This age-related MAC reduction is clinically important for dose adjustment in elderly patients.

Reference: Peck Hill Williams 2014 Pharmacology for Anaesthesia and Intensive Care