Meyer-Overton Hypothesis — FRCA Final MCQ
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Correct answer: B — Drug pKa and ionisation
The Meyer-Overton hypothesis (1899-1901) states that the potency of an anaesthetic agent (inverse of MAC) correlates with its lipid solubility (oil:gas partition coefficient). More lipid-soluble agents have lower MACs (more potent). This held true for all volatile agents for >100 years, though exceptions now exist (e.g., perfluorocarbon compounds with high lipid solubility but no anaesthetic effect), suggesting that specific molecular targets (GABA-A, glycine receptors) rather than simple lipid membrane disruption are responsible.
Reference: RCOA – 2023 – Pharmacology: mechanism of anaesthesia; Peck TE – 2014