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Meyer-Overton Correlation — FRCA Primary MCQ

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ModeratePharmacology - Inhalational AgentsMeyer-Overton CorrelationFRCA Primary

For conventional volatile anaesthetic agents, which statement best describes the Meyer–Overton correlation between the oil:gas partition coefficient and minimum alveolar concentration (MAC)?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — A high oil:gas partition coefficient indicates high potency and a low MAC

Explanation lettering: E = shown as A · D = shown as C · A = shown as D · C = shown as E

D is correct. The Meyer–Overton correlation relates anaesthetic potency to lipid solubility. For conventional inhaled anaesthetics, the product of MAC and the oil:gas partition coefficient is approximately constant. Therefore, a higher oil:gas coefficient is associated with greater potency and a lower MAC; MAC acts as an inverse index of volatile-agent potency. Options A and C reverse this relationship, while E incorrectly denies it. Option B confuses oil:gas with the blood:gas partition coefficient: blood solubility is a major determinant of the rate at which alveolar and brain partial pressures rise and therefore influences onset and offset. The Meyer–Overton relationship is an empirical correlation with recognised exceptions, which is why the stem specifies conventional volatile anaesthetic agents.

Reference: Royal College of Anaesthetists. 15 SBA questions with answers, inhalational anaesthetic question and explanation, 2012. https://www.rcoa.ac.uk/media/9836